# valgrind

## NAME



           valgrind - a suite of tools for debugging and profiling programs
    


## SYNOPSIS



    
           **valgrind**[_valgrind-options_] [_your-program_] [_your-program-options_]
    


## DESCRIPTION



           **Valgrind** is a flexible program for debugging and profiling Linux
           executables. It consists of a core, which provides a synthetic CPU
           in software, and a series of debugging and profiling tools. The
           architecture is modular, so that new tools can be created easily
           and without disturbing the existing structure.
    
           Some of the options described below work with all Valgrind tools,
           and some only work with a few or one. The section MEMCHECK OPTIONS
           and those below it describe tool-specific options.
    
           This manual page covers only basic usage and options. For more
           comprehensive information, please see the HTML documentation on
           your system: $INSTALL/share/doc/valgrind/html/index.html, or
           online: http://www.valgrind.org/docs/manual/index.html.
    


## TOOL SELECTION OPTIONS



           The single most important option.
    
           **--tool= <toolname> [default: memcheck]**
               Run the Valgrind tool called _toolname_ , e.g. memcheck,
               cachegrind, callgrind, helgrind, drd, massif, dhat, lackey,
               none, exp-bbv, etc.
    


## BASIC OPTIONS



           These options work with all tools.
    
           **-h --help**
               Show help for all options, both for the core and for the
               selected tool. If the option is repeated it is equivalent to
               giving **--help-debug**.
    
           **--help-debug**
               Same as **--help** , but also lists debugging options which usually
               are only of use to Valgrind's developers.
    
           **--version**
               Show the version number of the Valgrind core. Tools can have
               their own version numbers. There is a scheme in place to
               ensure that tools only execute when the core version is one
               they are known to work with. This was done to minimise the
               chances of strange problems arising from tool-vs-core version
               incompatibilities.
    
           **-q** , **--quiet**
               Run silently, and only print error messages. Useful if you are
               running regression tests or have some other automated test
               machinery.
    
           **-v** , **--verbose**
               Be more verbose. Gives extra information on various aspects of
               your program, such as: the shared objects loaded, the
               suppressions used, the progress of the instrumentation and
               execution engines, and warnings about unusual behaviour.
               Repeating the option increases the verbosity level.
    
           **--trace-children= <yes|no> [default: no]**
               When enabled, Valgrind will trace into sub-processes initiated
               via the _exec_ system call. This is necessary for multi-process
               programs.
    
               Note that Valgrind does trace into the child of a _fork_ (it
               would be difficult not to, since _fork_ makes an identical copy
               of a process), so this option is arguably badly named.
               However, most children of _fork_ calls immediately call _exec_
               anyway.
    
           **--trace-children-skip=patt1,patt2,...**
               This option only has an effect when **--trace-children=yes** is
               specified. It allows for some children to be skipped. The
               option takes a comma separated list of patterns for the names
               of child executables that Valgrind should not trace into.
               Patterns may include the metacharacters ?  and *, which have
               the usual meaning.
    
               This can be useful for pruning uninteresting branches from a
               tree of processes being run on Valgrind. But you should be
               careful when using it. When Valgrind skips tracing into an
               executable, it doesn't just skip tracing that executable, it
               also skips tracing any of that executable's child processes.
               In other words, the flag doesn't merely cause tracing to stop
               at the specified executables -- it skips tracing of entire
               process subtrees rooted at any of the specified executables.
    
           **--trace-children-skip-by-arg=patt1,patt2,...**
               This is the same as **--trace-children-skip** , with one
               difference: the decision as to whether to trace into a child
               process is made by examining the arguments to the child
               process, rather than the name of its executable.
    
           **--child-silent-after-fork= <yes|no> [default: no]**
               When enabled, Valgrind will not show any debugging or logging
               output for the child process resulting from a _fork_ call. This
               can make the output less confusing (although more misleading)
               when dealing with processes that create children. It is
               particularly useful in conjunction with _--trace-children=_. Use
               of this option is also strongly recommended if you are
               requesting XML output (_--xml=yes_), since otherwise the XML
               from child and parent may become mixed up, which usually makes
               it useless.
    
           **--vgdb= <no|yes|full> [default: yes]**
               Valgrind will provide "gdbserver" functionality when
               **--vgdb=yes** or **--vgdb=full** is specified. This allows an
               external GNU GDB debugger to control and debug your program
               when it runs on Valgrind.  **--vgdb=full** incurs significant
               performance overheads, but provides more precise breakpoints
               and watchpoints. See Debugging your program using Valgrind's
               gdbserver and GDB for a detailed description.
    
               If the embedded gdbserver is enabled but no gdb is currently
               being used, the vgdb command line utility can send "monitor
               commands" to Valgrind from a shell. The Valgrind core provides
               a set of Valgrind monitor commands. A tool can optionally
               provide tool specific monitor commands, which are documented
               in the tool specific chapter.
    
           **--vgdb-error= <number> [default: 999999999]**
               Use this option when the Valgrind gdbserver is enabled with
               **--vgdb=yes** or **--vgdb=full**. Tools that report errors will wait
               for "number" errors to be reported before freezing the program
               and waiting for you to connect with GDB. It follows that a
               value of zero will cause the gdbserver to be started before
               your program is executed. This is typically used to insert GDB
               breakpoints before execution, and also works with tools that
               do not report errors, such as Massif.
    
           **--vgdb-stop-at= <set> [default: none]**
               Use this option when the Valgrind gdbserver is enabled with
               **--vgdb=yes** or **--vgdb=full**. The Valgrind gdbserver will be
               invoked for each error after **--vgdb-error** have been reported.
               You can additionally ask the Valgrind gdbserver to be invoked
               for other events, specified in one of the following ways:
    
               •   a comma separated list of one or more of **startup exit**
                   **abexit valgrindabexit**.
    
                   The values **startup exit valgrindabexit** respectively
                   indicate to invoke gdbserver before your program is
                   executed, after the last instruction of your program, on
                   Valgrind abnormal exit (e.g. internal error, out of
                   memory, ...).
    
                   The option **abexit** is similar to **exit** but tells to invoke
                   gdbserver only when your application exits abnormally
                   (i.e. with an exit code different of 0).
    
                   Note: **startup** and **--vgdb-error=0** will both cause Valgrind
                   gdbserver to be invoked before your program is executed.
                   The **--vgdb-error=0** will in addition cause your program to
                   stop on all subsequent errors.
    
               •   **all** to specify the complete set. It is equivalent to
                   **--vgdb-stop-at=startup,exit,abexit,valgrindabexit**.
    
               •   **none** for the empty set.
    
           **--track-fds= <yes|no|all|bad> [default: no]**
               When enabled, Valgrind will track all file descriptor usage.
               It will produce errors for bad file descriptor usage like
               closing a file descriptor twice, using a file descriptor
               (number) that was never created, or passing an already closed
               file descriptor to a system call. It will also print out a
               list of open file descriptors on exit. Or on request, via the
               gdbserver monitor command _v.info open_fds_.
    
               When an error is generated, or when listing the still open
               file descriptors at exit, a stack backtrace of where the file
               was opened is printed. If the file descriptor has already been
               closed, it will also include a backtrace of where it was
               previously closed. Any error will include details relating to
               the file descriptor such as the file name or socket details.
    
               Use **all** to also include reporting on stdin, stdout and stderr
               (or other inherited file descriptors) at exit. If **bad** option
               is used, then exclude reporting on leaked file descriptors at
               exit and only produce errors about bad file decriptors usage.
    
           **--modify-fds= <no|yes|high> [default: no]**
               When enabled, when the program opens a new file descriptor,
               the highest available file descriptor is returned instead of
               the lowest one. Use **yes** to restrict the feature from the 0/1/2
               file descriptors as they're often used for stdout/stderr
               redirection.
    
           **--time-stamp= <yes|no> [default: no]**
               When enabled, each message is preceded with an indication of
               the elapsed wallclock time since startup, expressed as days,
               hours, minutes, seconds and milliseconds.
    
           **--log-fd= <number> [default: 2, stderr]**
               Specifies that Valgrind should send all of its messages to the
               specified file descriptor. The default, 2, is the standard
               error channel (stderr). Note that this may interfere with the
               client's own use of stderr, as Valgrind's output will be
               interleaved with any output that the client sends to stderr.
    
           **--log-file= <filename>**
               Specifies that Valgrind should send all of its messages to the
               specified file. If the file name is empty, it causes an abort.
               There are three special format specifiers that can be used in
               the file name.
    
               **%p** is replaced with the current process ID. This is very
               useful for program that invoke multiple processes. WARNING: If
               you use **--trace-children=yes** and your program invokes multiple
               processes OR your program forks without calling exec
               afterwards, and you don't use this specifier (or the **%q**
               specifier below), the Valgrind output from all those processes
               will go into one file, possibly jumbled up, and possibly
               incomplete. Note: If the program forks and calls exec
               afterwards, Valgrind output of the child from the period
               between fork and exec will be lost. Fortunately this gap is
               really tiny for most programs; and modern programs use
               posix_spawn anyway.
    
               **%n** is replaced with a file sequence number unique for this
               process. This is useful for processes that produces several
               files from the same filename template.
    
               **%q{FOO}** is replaced with the contents of the environment
               variable _FOO_. If the **{FOO}** part is malformed, it causes an
               abort. This specifier is rarely needed, but very useful in
               certain circumstances (eg. when running MPI programs). The
               idea is that you specify a variable which will be set
               differently for each process in the job, for example
               BPROC_RANK or whatever is applicable in your MPI setup. If the
               named environment variable is not set, it causes an abort.
               Note that in some shells, the **{** and **}** characters may need to
               be escaped with a backslash.
    
               **%%** is replaced with **%**.
    
               If an **%** is followed by any other character, it causes an
               abort.
    
               If the file name specifies a relative file name, it is put in
               the program's initial working directory: this is the current
               directory when the program started its execution after the
               fork or after the exec. If it specifies an absolute file name
               (ie. starts with '/') then it is put there.
    
           **--log-socket= <ip-address:port-number>**
               Specifies that Valgrind should send all of its messages to the
               specified port at the specified IP address. The port may be
               omitted, in which case port 1500 is used. If a connection
               cannot be made to the specified socket, Valgrind falls back to
               writing output to the standard error (stderr). This option is
               intended to be used in conjunction with the valgrind-listener
               program. For further details, see the commentary in the
               manual.
    
           **--enable-debuginfod= <no|yes> [default: yes]**
               When enabled Valgrind will attempt to download missing
               debuginfo from debuginfod servers if space-separated server
               URLs are present in the $DEBUGINFOD_URLS environment variable.
               This option is supported on Linux only.
    


## ERROR-RELATED OPTIONS



           These options are used by all tools that can report errors, e.g.
           Memcheck, but not Cachegrind.
    
           **--xml= <yes|no> [default: no]**
               When enabled, the important parts of the output (e.g. tool
               error messages) will be in XML format rather than plain text.
               Furthermore, the XML output will be sent to a different output
               channel than the plain text output. Therefore, you also must
               use one of **--xml-fd** , **--xml-file** or **--xml-socket** to specify
               where the XML is to be sent.
    
               Less important messages will still be printed in plain text,
               but because the XML output and plain text output are sent to
               different output channels (the destination of the plain text
               output is still controlled by **--log-fd** , **--log-file** and
               **--log-socket**) this should not cause problems.
    
               This option is aimed at making life easier for tools that
               consume Valgrind's output as input, such as GUI front ends.
               Currently this option works with Memcheck, Helgrind and DRD.
               The output format is specified in the file
               docs/internals/xml-output-protocol4.txt in the source tree for
               Valgrind 3.5.0 or later.
    
               The recommended options for a GUI to pass, when requesting XML
               output, are: **--xml=yes** to enable XML output, **--xml-file** to
               send the XML output to a (presumably GUI-selected) file,
               **--log-file** to send the plain text output to a second
               GUI-selected file, **--child-silent-after-fork=yes** , and **-q** to
               restrict the plain text output to critical error messages
               created by Valgrind itself. For example, failure to read a
               specified suppressions file counts as a critical error
               message. In this way, for a successful run the text output
               file will be empty. But if it isn't empty, then it will
               contain important information which the GUI user should be
               made aware of.
    
           **--xml-fd= <number> [default: -1, disabled]**
               Specifies that Valgrind should send its XML output to the
               specified file descriptor. It must be used in conjunction with
               **--xml=yes**.
    
           **--xml-file= <filename>**
               Specifies that Valgrind should send its XML output to the
               specified file. It must be used in conjunction with **--xml=yes**.
               Any **%p** or **%q** sequences appearing in the filename are expanded
               in exactly the same way as they are for **--log-file**. See the
               description of --log-file for details.
    
           **--xml-socket= <ip-address:port-number>**
               Specifies that Valgrind should send its XML output the
               specified port at the specified IP address. It must be used in
               conjunction with **--xml=yes**. The form of the argument is the
               same as that used by **--log-socket**. See the description of
               **--log-socket** for further details.
    
           **--xml-user-comment= <string>**
               Embeds an extra user comment string at the start of the XML
               output. Only works when **--xml=yes** is specified; ignored
               otherwise.
    
           **--demangle= <yes|no> [default: yes]**
               Enable/disable automatic demangling (decoding) of C++, D,
               Rust, Java, Ada names. Enabled by default. When enabled,
               Valgrind will attempt to translate encoded names in the listed
               languages back to something approaching the original. Note
               that the callgrind tool always disables Ada demangling in
               order to differentiate overloaded functions and procedures in
               the callgraph. The demangler handles symbols mangled by g++
               versions 2.X, 3.X and 4.X.
    
               An important fact about demangling is that function names
               mentioned in suppressions files should be in their mangled
               form. Valgrind does not demangle function names when searching
               for applicable suppressions, because to do otherwise would
               make suppression file contents dependent on the state of
               Valgrind's demangling machinery, and also slow down
               suppression matching.
    
           **--num-callers= <number> [default: 12]**
               Specifies the maximum number of entries shown in stack traces
               that identify program locations. Note that errors are commoned
               up using only the top four function locations (the place in
               the current function, and that of its three immediate
               callers). So this doesn't affect the total number of errors
               reported.
    
               The maximum value for this is 500. Note that higher settings
               will make Valgrind run a bit more slowly and take a bit more
               memory, but can be useful when working with programs with
               deeply-nested call chains.
    
           **--unw-stack-scan-thresh= <number> [default: 0] **,
           **--unw-stack-scan-frames= <number> [default: 5]**
               Stack-scanning support is available only on ARM targets.
    
               These flags enable and control stack unwinding by stack
               scanning. When the normal stack unwinding mechanisms -- usage
               of Dwarf CFI records, and frame-pointer following -- fail,
               stack scanning may be able to recover a stack trace.
    
               Note that stack scanning is an imprecise, heuristic mechanism
               that may give very misleading results, or none at all. It
               should be used only in emergencies, when normal unwinding
               fails, and it is important to nevertheless have stack traces.
    
               Stack scanning is a simple technique: the unwinder reads words
               from the stack, and tries to guess which of them might be
               return addresses, by checking to see if they point just after
               ARM or Thumb call instructions. If so, the word is added to
               the backtrace.
    
               The main danger occurs when a function call returns, leaving
               its return address exposed, and a new function is called, but
               the new function does not overwrite the old address. The
               result of this is that the backtrace may contain entries for
               functions which have already returned, and so be very
               confusing.
    
               A second limitation of this implementation is that it will
               scan only the page (4KB, normally) containing the starting
               stack pointer. If the stack frames are large, this may result
               in only a few (or not even any) being present in the trace.
               Also, if you are unlucky and have an initial stack pointer
               near the end of its containing page, the scan may miss all
               interesting frames.
    
               By default stack scanning is disabled. The normal use case is
               to ask for it when a stack trace would otherwise be very
               short. So, to enable it, use --unw-stack-scan-thresh=number.
               This requests Valgrind to try using stack scanning to "extend"
               stack traces which contain fewer than number frames.
    
               If stack scanning does take place, it will only generate at
               most the number of frames specified by
               --unw-stack-scan-frames. Typically, stack scanning generates
               so many garbage entries that this value is set to a low value
               (5) by default. In no case will a stack trace larger than the
               value specified by --num-callers be created.
    
           **--error-limit= <yes|no> [default: yes]**
               When enabled, Valgrind stops reporting errors after 10,000,000
               in total, or 1,000 different ones, have been seen. This is to
               stop the error tracking machinery from becoming a huge
               performance overhead in programs with many errors.
    
           **--error-exitcode= <number> [default: 0]**
               Specifies an alternative exit code to return if Valgrind
               reported any errors in the run. When set to the default value
               (zero), the return value from Valgrind will always be the
               return value of the process being simulated. When set to a
               nonzero value, that value is returned instead, if Valgrind
               detects any errors. This is useful for using Valgrind as part
               of an automated test suite, since it makes it easy to detect
               test cases for which Valgrind has reported errors, just by
               inspecting return codes. When set to a nonzero value and
               Valgrind detects no error, the return value of Valgrind will
               be the return value of the program being simulated.
    
           **--exit-on-first-error= <yes|no> [default: no]**
               If this option is enabled, Valgrind exits on the first error.
               A nonzero exit value must be defined using --error-exitcode
               option. Useful if you are running regression tests or have
               some other automated test machinery.
    
           **--error-markers= <begin>,<end> [default: none]**
               When errors are output as plain text (i.e. XML not used),
               **--error-markers** instructs to output a line containing the
               **begin**(**end**) string before (after) each error.
    
               Such marker lines facilitate searching for errors and/or
               extracting errors in an output file that contain valgrind
               errors mixed with the program output.
    
               Note that empty markers are accepted. So, only using a begin
               (or an end) marker is possible.
    
           **--show-error-list=no|yes|all [default: no]**
               If this option is yes, for tools that report errors, valgrind
               will show the list of detected errors and the list of used
               suppressions at exit. The value all indicates to also show the
               list of suppressed errors.
    
               Note that at verbosity 2 and above, valgrind automatically
               shows the list of detected errors and the list of used
               suppressions at exit, unless **--show-error-list=no** is selected.
    
           **-s**
               Specifying **-s** is equivalent to **--show-error-list=yes**.
    
           **--sigill-diagnostics= <yes|no> [default: yes]**
               Enable/disable printing of illegal instruction diagnostics.
               Enabled by default, but defaults to disabled when **--quiet** is
               given. The default can always be explicitly overridden by
               giving this option.
    
               When enabled, a warning message will be printed, along with
               some diagnostics, whenever an instruction is encountered that
               Valgrind cannot decode or translate, before the program is
               given a SIGILL signal. Often an illegal instruction indicates
               a bug in the program or missing support for the particular
               instruction in Valgrind. But some programs do deliberately try
               to execute an instruction that might be missing and trap the
               SIGILL signal to detect processor features. Using this flag
               makes it possible to avoid the diagnostic output that you
               would otherwise get in such cases.
    
           **--keep-debuginfo= <yes|no> [default: no]**
               When enabled, keep ("archive") symbols and all other debuginfo
               for unloaded code. This allows saved stack traces to include
               file/line info for code that has been dlclose'd (or similar).
               Be careful with this, since it can lead to unbounded memory
               use for programs which repeatedly load and unload shared
               objects.
    
               Some tools and some functionalities have only limited support
               for archived debug info. Memcheck fully supports it.
               Generally, tools that report errors can use archived debug
               info to show the error stack traces. The known limitations
               are: Helgrind's past access stack trace of a race condition is
               does not use archived debug info. Massif (and more generally
               the xtree Massif output format) does not make use of archived
               debug info. Only Memcheck has been (somewhat) tested with
               **--keep-debuginfo=yes** , so other tools may have unknown
               limitations.
    
           **--show-below-main= <yes|no> [default: no]**
               By default, stack traces for errors do not show any functions
               that appear beneath **main** because most of the time it's
               uninteresting C library stuff and/or gobbledygook.
               Alternatively, if **main** is not present in the stack trace,
               stack traces will not show any functions below **main** -like
               functions such as glibc's **__libc_start_main**. Furthermore, if
               **main** -like functions are present in the trace, they are
               normalised as **(below main)** , in order to make the output more
               deterministic.
    
               If this option is enabled, all stack trace entries will be
               shown and **main** -like functions will not be normalised.
    
           **--fullpath-after= <string> [default: don't show source paths]**
               By default Valgrind only shows the filenames in stack traces,
               but not full paths to source files. When using Valgrind in
               large projects where the sources reside in multiple different
               directories, this can be inconvenient.  **--fullpath-after**
               provides a flexible solution to this problem. When this option
               is present, the path to each source file is shown, with the
               following all-important caveat: if **string** is found in the
               path, then the path up to and including **string** is omitted,
               else the path is shown unmodified. Note that **string** is not
               required to be a prefix of the path.
    
               For example, consider a file named
               /home/janedoe/blah/src/foo/bar/xyzzy.c. Specifying
               **--fullpath-after=/home/janedoe/blah/src/** will cause Valgrind
               to show the name as foo/bar/xyzzy.c.
    
               Because the string is not required to be a prefix,
               **--fullpath-after=src/** will produce the same output. This is
               useful when the path contains arbitrary machine-generated
               characters. For example, the path
               /my/build/dir/C32A1B47/blah/src/foo/xyzzy can be pruned to
               foo/xyzzy using **--fullpath-after=/blah/src/**.
    
               If you simply want to see the full path, just specify an empty
               string: **--fullpath-after=**. This isn't a special case, merely a
               logical consequence of the above rules.
    
               Finally, you can use **--fullpath-after** multiple times. Any
               appearance of it causes Valgrind to switch to producing full
               paths and applying the above filtering rule. Each produced
               path is compared against all the **--fullpath-after** -specified
               strings, in the order specified. The first string to match
               causes the path to be truncated as described above. If none
               match, the full path is shown. This facilitates chopping off
               prefixes when the sources are drawn from a number of unrelated
               directories.
    
           **--extra-debuginfo-path= <path> [default: undefined and unused]**
               By default Valgrind searches in several well-known paths for
               debug objects, such as /usr/lib/debug/.
    
               However, there may be scenarios where you may wish to put
               debug objects at an arbitrary location, such as external
               storage when running Valgrind on a mobile device with limited
               local storage. Another example might be a situation where you
               do not have permission to install debug object packages on the
               system where you are running Valgrind.
    
               In these scenarios, you may provide an absolute path as an
               extra, final place for Valgrind to search for debug objects by
               specifying **--extra-debuginfo-path=/path/to/debug/objects**. The
               given path will be prepended to the absolute path name of the
               searched-for object. For example, if Valgrind is looking for
               the debuginfo for /w/x/y/zz.so and
               **--extra-debuginfo-path=/a/b/c** is specified, it will look for a
               debug object at /a/b/c/w/x/y/zz.so.
    
               This flag should only be specified once. If it is specified
               multiple times, only the last instance is honoured.
    
           **--debuginfo-server=ipaddr:port [default: undefined and unused]**
               This is a new, experimental, feature introduced in version
               3.9.0.
    
               In some scenarios it may be convenient to read debuginfo from
               objects stored on a different machine. With this flag,
               Valgrind will query a debuginfo server running on ipaddr and
               listening on port port, if it cannot find the debuginfo object
               in the local filesystem.
    
               The debuginfo server must accept TCP connections on port port.
               The debuginfo server is contained in the source file
               auxprogs/valgrind-di-server.c. It will only serve from the
               directory it is started in.  port defaults to 1500 in both
               client and server if not specified.
    
               If Valgrind looks for the debuginfo for /w/x/y/zz.so by using
               the debuginfo server, it will strip the pathname components
               and merely request zz.so on the server. That in turn will look
               only in its current working directory for a matching debuginfo
               object.
    
               The debuginfo data is transmitted in small fragments (8 KB) as
               requested by Valgrind. Each block is compressed using LZO to
               reduce transmission time. The implementation has been tuned
               for best performance over a single-stage 802.11g (WiFi)
               network link.
    
               Note that checks for matching primary vs debug objects, using
               GNU debuglink CRC scheme, are performed even when using the
               debuginfo server. To disable such checking, you need to also
               specify --allow-mismatched-debuginfo=yes.
    
               By default the Valgrind build system will build
               valgrind-di-server for the target platform, which is almost
               certainly not what you want. So far we have been unable to
               find out how to get automake/autoconf to build it for the
               build platform. If you want to use it, you will have to
               recompile it by hand using the command shown at the top of
               auxprogs/valgrind-di-server.c.
    
               Valgrind can also download debuginfo via debuginfod. See the
               DEBUGINFOD section for more information.
    
           **--allow-mismatched-debuginfo=no|yes [no]**
               When reading debuginfo from separate debuginfo objects,
               Valgrind will by default check that the main and debuginfo
               objects match, using the GNU debuglink mechanism. This
               guarantees that it does not read debuginfo from out of date
               debuginfo objects, and also ensures that Valgrind can't crash
               as a result of mismatches.
    
               This check can be overridden using
               --allow-mismatched-debuginfo=yes. This may be useful when the
               debuginfo and main objects have not been split in the proper
               way. Be careful when using this, though: it disables all
               consistency checking, and Valgrind has been observed to crash
               when the main and debuginfo objects don't match.
    
           **--suppressions= <filename> [default:**
           **$PREFIX/lib/valgrind/default.supp]**
               Specifies an extra file from which to read descriptions of
               errors to suppress. You may use up to 100 extra suppression
               files.
    
           **--gen-suppressions= <yes|no|all> [default: no]**
               When set to _yes_ , Valgrind will pause after every error shown
               and print the line:
    
                       ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----
    
               Pressing _Ret_ , or _N Ret_ or _n Ret_ , causes Valgrind continue
               execution without printing a suppression for this error.
    
               Pressing _Y Ret_ or _y Ret_ causes Valgrind to write a suppression
               for this error. You can then cut and paste it into a
               suppression file if you don't want to hear about the error in
               the future.
    
               When set to _all_ , Valgrind will print a suppression for every
               reported error, without querying the user.
    
               This option is particularly useful with C++ programs, as it
               prints out the suppressions with mangled names, as required.
    
               Note that the suppressions printed are as specific as
               possible. You may want to common up similar ones, by adding
               wildcards to function names, and by using frame-level
               wildcards. The wildcarding facilities are powerful yet
               flexible, and with a bit of careful editing, you may be able
               to suppress a whole family of related errors with only a few
               suppressions.
    
               Sometimes two different errors are suppressed by the same
               suppression, in which case Valgrind will output the
               suppression more than once, but you only need to have one copy
               in your suppression file (but having more than one won't cause
               problems). Also, the suppression name is given as <insert a
               suppression name here>; the name doesn't really matter, it's
               only used with the **-v** option which prints out all used
               suppression records.
    
           **--input-fd= <number> [default: 0, stdin]**
               When using **--gen-suppressions=yes** , Valgrind will stop so as to
               read keyboard input from you when each error occurs. By
               default it reads from the standard input (stdin), which is
               problematic for programs which close stdin. This option allows
               you to specify an alternative file descriptor from which to
               read input.
    
           **--dsymutil=no|yes [yes]**
               This option is only relevant when running Valgrind on macOS.
    
               macOS uses a deferred debug information (debuginfo) linking
               scheme. When object files containing debuginfo are linked into
               a .dylib or an executable, the debuginfo is not copied into
               the final file. Instead, the debuginfo must be linked manually
               by running dsymutil, a system-provided utility, on the
               executable or .dylib. The resulting combined debuginfo is
               placed in a directory alongside the executable or .dylib, but
               with the extension .dSYM.
    
               With **--dsymutil=no** , Valgrind will detect cases where the .dSYM
               directory is either missing, or is present but does not appear
               to match the associated executable or .dylib, most likely
               because it is out of date. In these cases, Valgrind will print
               a warning message but take no further action.
    
               With **--dsymutil=yes** , Valgrind will, in such cases,
               automatically run dsymutil as necessary to bring the debuginfo
               up to date. For all practical purposes, if you always use
               **--dsymutil=yes** , then there is never any need to run dsymutil
               manually or as part of your applications's build system, since
               Valgrind will run it as necessary.
    
               Valgrind will not attempt to run dsymutil on any executable or
               library in /usr/, /bin/, /sbin/, /opt/, /sw/, /System/,
               /Library/ or /Applications/ since dsymutil will always fail in
               such situations. It fails both because the debuginfo for such
               pre-installed system components is not available anywhere, and
               also because it would require write privileges in those
               directories.
    
               Be careful when using **--dsymutil=yes** , since it will cause
               pre-existing .dSYM directories to be silently deleted and
               re-created. Also note that dsymutil is quite slow, sometimes
               excessively so.
    
           **--max-stackframe= <number> [default: 2000000]**
               The maximum size of a stack frame. If the stack pointer moves
               by more than this amount then Valgrind will assume that the
               program is switching to a different stack.
    
               You may need to use this option if your program has large
               stack-allocated arrays. Valgrind keeps track of your program's
               stack pointer. If it changes by more than the threshold
               amount, Valgrind assumes your program is switching to a
               different stack, and Memcheck behaves differently than it
               would for a stack pointer change smaller than the threshold.
               Usually this heuristic works well. However, if your program
               allocates large structures on the stack, this heuristic will
               be fooled, and Memcheck will subsequently report large numbers
               of invalid stack accesses. This option allows you to change
               the threshold to a different value.
    
               You should only consider use of this option if Valgrind's
               debug output directs you to do so. In that case it will tell
               you the new threshold you should specify.
    
               In general, allocating large structures on the stack is a bad
               idea, because you can easily run out of stack space,
               especially on systems with limited memory or which expect to
               support large numbers of threads each with a small stack, and
               also because the error checking performed by Memcheck is more
               effective for heap-allocated data than for stack-allocated
               data. If you have to use this option, you may wish to consider
               rewriting your code to allocate on the heap rather than on the
               stack.
    
           **--main-stacksize= <number> [default: use current 'ulimit' value]**
               Specifies the size of the main thread's stack.
    
               To simplify its memory management, Valgrind reserves all
               required space for the main thread's stack at startup. That
               means it needs to know the required stack size at startup.
    
               By default, Valgrind uses the current "ulimit" value for the
               stack size, or 16 MB, whichever is lower. In many cases this
               gives a stack size in the range 8 to 16 MB, which almost never
               overflows for most applications.
    
               If you need a larger total stack size, use **--main-stacksize** to
               specify it. Only set it as high as you need, since reserving
               far more space than you need (that is, hundreds of megabytes
               more than you need) constrains Valgrind's memory allocators
               and may reduce the total amount of memory that Valgrind can
               use. This is only really of significance on 32-bit machines.
    
               On Linux, you may request a stack of size up to 2GB. Valgrind
               will stop with a diagnostic message if the stack cannot be
               allocated.
    
               **--main-stacksize** only affects the stack size for the program's
               initial thread. It has no bearing on the size of thread
               stacks, as Valgrind does not allocate those.
    
               You may need to use both **--main-stacksize** and **--max-stackframe**
               together. It is important to understand that **--main-stacksize**
               sets the maximum total stack size, whilst **--max-stackframe**
               specifies the largest size of any one stack frame. You will
               have to work out the **--main-stacksize** value for yourself
               (usually, if your applications segfaults). But Valgrind will
               tell you the needed **--max-stackframe** size, if necessary.
    
               As discussed further in the description of **--max-stackframe** , a
               requirement for a large stack is a sign of potential
               portability problems. You are best advised to place all large
               data in heap-allocated memory.
    
           **--max-threads= <number> [default: 500]**
               By default, Valgrind can handle to up to 500 threads.
               Occasionally, that number is too small. Use this option to
               provide a different limit. E.g.  --max-threads=3000.
    
           **--realloc-zero-bytes-frees=yes|no [default: yes for glibc no**
           **otherwise]**
               The behaviour of realloc() with a size of zero is
               implementation defined in C17 and undefined in C23. Valgrind
               tries to work in the same way as the underlying system and C
               runtime library that it was configured and built on. However,
               if you use a different C runtime library then this default may
               be wrong. If the value is **yes** then _realloc_ will deallocate the
               memory and return NULL. If the value is **no** then _realloc_ will
               not deallocate the memory and the size will be handled as
               though it were one byte.
    
               As an example, if you use Valgrind installed via a package on
               a Linux distro using GNU libc but link your test executable
               with musl libc or the JEMalloc library then consider using
               --realloc-zero-bytes-frees=no.
    
               Address Sanitizer has a similar and even wordier option
               allocator_frees_and_returns_null_on_realloc_zero.
    


## MALLOC()-RELATED OPTIONS



           For tools that use their own version of malloc (e.g. Memcheck,
           Massif, Helgrind, DRD), the following options apply.
    
           **--alignment= <number> [default: 8 or 16, depending on the platform]**
               By default Valgrind's **malloc** , **realloc** , etc, return a block
               whose starting address is 8-byte aligned or 16-byte aligned
               (the value depends on the platform and matches the platform
               default). This option allows you to specify a different
               alignment. The supplied value must be greater than or equal to
               the default, less than or equal to 4096, and must be a power
               of two.
    
           **--redzone-size= <number> [default: depends on the tool]**
               Valgrind's **malloc, realloc,** etc, add padding blocks before and
               after each heap block allocated by the program being run. Such
               padding blocks are called redzones. The default value for the
               redzone size depends on the tool. For example, Memcheck adds
               and protects a minimum of 16 bytes before and after each block
               allocated by the client. This allows it to detect block
               underruns or overruns of up to 16 bytes.
    
               Increasing the redzone size makes it possible to detect
               overruns of larger distances, but increases the amount of
               memory used by Valgrind. Decreasing the redzone size will
               reduce the memory needed by Valgrind but also reduces the
               chances of detecting over/underruns, so is not recommended.
    
           **--xtree-memory=none|allocs|full [none]**
               Tools replacing Valgrind's **malloc, realloc,** etc, can
               optionally produce an execution tree detailing which piece of
               code is responsible for heap memory usage. See Execution Trees
               for a detailed explanation about execution trees.
    
               When set to _none_ , no memory execution tree is produced.
    
               When set to _allocs_ , the memory execution tree gives the
               current number of allocated bytes and the current number of
               allocated blocks.
    
               When set to _full_ , the memory execution tree gives 6 different
               measurements : the current number of allocated bytes and
               blocks (same values as for _allocs_), the total number of
               allocated bytes and blocks, the total number of freed bytes
               and blocks.
    
               Note that the overhead in cpu and memory to produce an xtree
               depends on the tool. The overhead in cpu is small for the
               value _allocs_ , as the information needed to produce this report
               is maintained in any case by the tool. For massif and
               helgrind, specifying _full_ implies to capture a stack trace for
               each free operation, while normally these tools only capture
               an allocation stack trace. For Memcheck, the cpu overhead for
               the value _full_ is small, as this can only be used in
               combination with **--keep-stacktraces=alloc-and-free** or
               **--keep-stacktraces=alloc-then-free** , which already records a
               stack trace for each free operation. The memory overhead
               varies between 5 and 10 words per unique stacktrace in the
               xtree, plus the memory needed to record the stack trace for
               the free operations, if needed specifically for the xtree.
    
           **--xtree-memory-file= <filename> [default: xtmemory.kcg.%p]**
               Specifies that Valgrind should produce the xtree memory report
               in the specified file. Any **%p** or **%q** sequences appearing in the
               filename are expanded in exactly the same way as they are for
               **--log-file**. See the description of --log-file for details.
    
               If the filename contains the extension **.ms** , then the produced
               file format will be a massif output file format. If the
               filename contains the extension **.kcg** or no extension is
               provided or recognised, then the produced file format will be
               a callgrind output format.
    
               See Execution Trees for a detailed explanation about execution
               trees formats.
    


## UNCOMMON OPTIONS



           These options apply to all tools, as they affect certain obscure
           workings of the Valgrind core. Most people won't need to use them.
    
           **--smc-check= <none|stack|all|all-non-file> [default: all-non-file**
           **for x86/amd64/s390x, stack for other archs]**
               This option controls Valgrind's detection of self-modifying
               code. If no checking is done, when a program executes some
               code, then overwrites it with new code, and executes the new
               code, Valgrind will continue to execute the translations it
               made for the old code. This will likely lead to incorrect
               behaviour and/or crashes.
    
               For "modern" architectures -- anything that's not x86, amd64
               or s390x -- the default is _stack_. This is because a correct
               program must take explicit action to reestablish D-I cache
               coherence following code modification. Valgrind observes and
               honours such actions, with the result that self-modifying code
               is transparently handled with zero extra cost.
    
               For x86, amd64 and s390x, the program is not required to
               notify the hardware of required D-I coherence syncing. Hence
               the default is _all-non-file_ , which covers the normal case of
               generating code into an anonymous (non-file-backed) mmap'd
               area.
    
               The meanings of the four available settings are as follows. No
               detection (_none_), detect self-modifying code on the stack
               (which is used by GCC to implement nested functions) (_stack_),
               detect self-modifying code everywhere (_all_), and detect
               self-modifying code everywhere except in file-backed mappings
               (_all-non-file_).
    
               Running with _all_ will slow Valgrind down noticeably. Running
               with _none_ will rarely speed things up, since very little code
               gets dynamically generated in most programs. The
               **VALGRIND_DISCARD_TRANSLATIONS** client request is an alternative
               to **--smc-check=all** and **--smc-check=all-non-file** that requires
               more programmer effort but allows Valgrind to run your program
               faster, by telling it precisely when translations need to be
               re-made.
    
               **--smc-check=all-non-file** provides a cheaper but more limited
               version of **--smc-check=all**. It adds checks to any translations
               that do not originate from file-backed memory mappings.
               Typical applications that generate code, for example JITs in
               web browsers, generate code into anonymous mmaped areas,
               whereas the "fixed" code of the browser always lives in
               file-backed mappings.  **--smc-check=all-non-file** takes
               advantage of this observation, limiting the overhead of
               checking to code which is likely to be JIT generated.
    
           **--read-inline-info= <yes|no> [default: see below]**
               When enabled, Valgrind will read information about inlined
               function calls from DWARF3 debug info. This slows Valgrind
               startup and makes it use more memory (typically for each
               inlined piece of code, 6 words and space for the function
               name), but it results in more descriptive stacktraces.
               Currently, this functionality is enabled by default only for
               Linux, FreeBSD, Android and Solaris targets and only for the
               tools Memcheck, Massif, Helgrind and DRD. Here is an example
               of some stacktraces with **--read-inline-info=no** :
    
                   ==15380== Conditional jump or move depends on uninitialised value(s)
                   ==15380==    at 0x80484EA: main (inlinfo.c:6)
                   ==15380==
                   ==15380== Conditional jump or move depends on uninitialised value(s)
                   ==15380==    at 0x8048550: fun_noninline (inlinfo.c:6)
                   ==15380==    by 0x804850E: main (inlinfo.c:34)
                   ==15380==
                   ==15380== Conditional jump or move depends on uninitialised value(s)
                   ==15380==    at 0x8048520: main (inlinfo.c:6)
    
               And here are the same errors with **--read-inline-info=yes** :
    
                   ==15377== Conditional jump or move depends on uninitialised value(s)
                   ==15377==    at 0x80484EA: fun_d (inlinfo.c:6)
                   ==15377==    by 0x80484EA: fun_c (inlinfo.c:14)
                   ==15377==    by 0x80484EA: fun_b (inlinfo.c:20)
                   ==15377==    by 0x80484EA: fun_a (inlinfo.c:26)
                   ==15377==    by 0x80484EA: main (inlinfo.c:33)
                   ==15377==
                   ==15377== Conditional jump or move depends on uninitialised value(s)
                   ==15377==    at 0x8048550: fun_d (inlinfo.c:6)
                   ==15377==    by 0x8048550: fun_noninline (inlinfo.c:41)
                   ==15377==    by 0x804850E: main (inlinfo.c:34)
                   ==15377==
                   ==15377== Conditional jump or move depends on uninitialised value(s)
                   ==15377==    at 0x8048520: fun_d (inlinfo.c:6)
                   ==15377==    by 0x8048520: main (inlinfo.c:35)
    
           **--read-var-info= <yes|no> [default: no]**
               When enabled, Valgrind will read information about variable
               types and locations from DWARF3 debug info. This slows
               Valgrind startup significantly and makes it use significantly
               more memory, but for the tools that can take advantage of it
               (Memcheck, Helgrind, DRD) it can result in more precise error
               messages. For example, here are some standard errors issued by
               Memcheck:
    
                   ==15363== Uninitialised byte(s) found during client check request
                   ==15363==    at 0x80484A9: croak (varinfo1.c:28)
                   ==15363==    by 0x8048544: main (varinfo1.c:55)
                   ==15363==  Address 0x80497f7 is 7 bytes inside data symbol "global_i2"
                   ==15363==
                   ==15363== Uninitialised byte(s) found during client check request
                   ==15363==    at 0x80484A9: croak (varinfo1.c:28)
                   ==15363==    by 0x8048550: main (varinfo1.c:56)
                   ==15363==  Address 0xbea0d0cc is on thread 1's stack
                   ==15363==  in frame #1, created by main (varinfo1.c:45)
    
               And here are the same errors with **--read-var-info=yes** :
    
                   ==15370== Uninitialised byte(s) found during client check request
                   ==15370==    at 0x80484A9: croak (varinfo1.c:28)
                   ==15370==    by 0x8048544: main (varinfo1.c:55)
                   ==15370==  Location 0x80497f7 is 0 bytes inside global_i2[7],
                   ==15370==  a global variable declared at varinfo1.c:41
                   ==15370==
                   ==15370== Uninitialised byte(s) found during client check request
                   ==15370==    at 0x80484A9: croak (varinfo1.c:28)
                   ==15370==    by 0x8048550: main (varinfo1.c:56)
                   ==15370==  Location 0xbeb4a0cc is 0 bytes inside local var "local"
                   ==15370==  declared at varinfo1.c:46, in frame #1 of thread 1
    
           **--vgdb-poll= <number> [default: 5000]**
               As part of its main loop, the Valgrind scheduler will poll to
               check if some activity (such as an external command or some
               input from a gdb) has to be handled by gdbserver. This
               activity poll will be done after having run the given number
               of basic blocks (or slightly more than the given number of
               basic blocks). This poll is quite cheap so the default value
               is set relatively low. You might further decrease this value
               if vgdb cannot use ptrace system call to interrupt Valgrind if
               all threads are (most of the time) blocked in a system call.
    
           **--vgdb-shadow-registers=no|yes [default: no]**
               When activated, gdbserver will expose the Valgrind shadow
               registers to GDB. With this, the value of the Valgrind shadow
               registers can be examined or changed using GDB. Exposing
               shadow registers only works with GDB version 7.1 or later.
    
           **--vgdb-prefix= <prefix> [default: /tmp/vgdb-pipe]**
               To communicate with gdb/vgdb, the Valgrind gdbserver creates 3
               files (2 named FIFOs and a mmap shared memory file). The
               prefix option controls the directory and prefix for the
               creation of these files.
    
           **--run-libc-freeres= <yes|no> [default: yes]**
               This option is only relevant when running Valgrind on Linux
               with GNU libc.
    
               The GNU C library (**libc.so**), which is used by all programs,
               may allocate memory for its own uses. Usually it doesn't
               bother to free that memory when the program ends—there would
               be no point, since the Linux kernel reclaims all process
               resources when a process exits anyway, so it would just slow
               things down.
    
               The glibc authors realised that this behaviour causes leak
               checkers, such as Valgrind, to falsely report leaks in glibc,
               when a leak check is done at exit. In order to avoid this,
               they provided a routine called **__libc_freeres** specifically to
               make glibc release all memory it has allocated. Memcheck
               therefore tries to run **__libc_freeres** at exit.
    
               Unfortunately, in some very old versions of glibc,
               **__libc_freeres** is sufficiently buggy to cause segmentation
               faults. This was particularly noticeable on Red Hat 7.1. So
               this option is provided in order to inhibit the run of
               **__libc_freeres**. If your program seems to run fine on Valgrind,
               but segfaults at exit, you may find that **--run-libc-freeres=no**
               fixes that, although at the cost of possibly falsely reporting
               space leaks in libc.so.
    
           **--run-cxx-freeres= <yes|no> [default: yes]**
               This option is only relevant when running Valgrind on Linux,
               FreeBSD or Solaris C++ programs using libstdc++.
    
               The GNU Standard C++ library (**libstdc++.so**), which is used by
               all C++ programs compiled with g++, may allocate memory for
               its own uses. Usually it doesn't bother to free that memory
               when the program ends—there would be no point, since the
               kernel reclaims all process resources when a process exits
               anyway, so it would just slow things down.
    
               The gcc authors realised that this behaviour causes leak
               checkers, such as Valgrind, to falsely report leaks in
               libstdc++, when a leak check is done at exit. In order to
               avoid this, they provided a routine called
               **__gnu_cxx::__freeres** specifically to make libstdc++ release
               all memory it has allocated. Memcheck therefore tries to run
               **__gnu_cxx::__freeres** at exit.
    
               For the sake of flexibility and unforeseen problems with
               **__gnu_cxx::__freeres** , option **--run-cxx-freeres=no** exists,
               although at the cost of possibly falsely reporting space leaks
               in libstdc++.so.
    
           **--sim-hints=hint1,hint2,...**
               Pass miscellaneous hints to Valgrind which slightly modify the
               simulated behaviour in nonstandard or dangerous ways, possibly
               to help the simulation of strange features. By default no
               hints are enabled. Use with caution! Currently known hints
               are:
    
               •   **lax-ioctls:** Be very lax about ioctl handling; the only
                   assumption is that the size is correct. Doesn't require
                   the full buffer to be initialised when writing. Without
                   this, using some device drivers with a large number of
                   strange ioctl commands becomes very tiresome.
    
               •   **fuse-compatible:** Enable special handling for certain
                   system calls that may block in a FUSE file-system. This
                   may be necessary when running Valgrind on a multi-threaded
                   program that uses one thread to manage a FUSE file-system
                   and another thread to access that file-system.
    
               •   **enable-outer:** Enable some special magic needed when the
                   program being run is itself Valgrind.
    
               •   **no-inner-prefix:** Disable printing a prefix **> **in front of
                   each stdout or stderr output line in an inner Valgrind
                   being run by an outer Valgrind. This is useful when
                   running Valgrind regression tests in an outer/inner setup.
                   Note that the prefix **> **will always be printed in front of
                   the inner debug logging lines.
    
               •   **no-nptl-pthread-stackcache:** This hint is only relevant
                   when running Valgrind on Linux; it is ignored on FreeBSD,
                   Solaris and macOS.
    
                   The GNU glibc pthread library (**libpthread.so**), which is
                   used by pthread programs, maintains a cache of pthread
                   stacks. When a pthread terminates, the memory used for the
                   pthread stack and some thread local storage related data
                   structure are not always directly released. This memory is
                   kept in a cache (up to a certain size), and is re-used if
                   a new thread is started.
    
                   This cache causes the helgrind tool to report some false
                   positive race condition errors on this cached memory, as
                   helgrind does not understand the internal glibc cache
                   synchronisation primitives. So, when using helgrind,
                   disabling the cache helps to avoid false positive race
                   conditions, in particular when using thread local storage
                   variables (e.g. variables using the **__thread** qualifier).
    
                   When using the memcheck tool, disabling the cache ensures
                   the memory used by glibc to handle __thread variables is
                   directly released when a thread terminates.
    
                   Note: Valgrind disables the cache using some internal
                   knowledge of the glibc stack cache implementation and by
                   examining the debug information of the pthread library.
                   This technique is thus somewhat fragile and might not work
                   for all glibc versions. This has been successfully tested
                   with various glibc versions (e.g. 2.11, 2.16, 2.18) on
                   various platforms.
    
               •   **lax-doors:**(Solaris only) Be very lax about door syscall
                   handling over unrecognised door file descriptors. Does not
                   require that full buffer is initialised when writing.
                   Without this, programs using libdoor(3LIB) functionality
                   with completely proprietary semantics may report large
                   number of false positives.
    
               •   **fallback-llsc:**(MIPS and ARM64 only): Enables an
                   alternative implementation of Load-Linked (LL) and
                   Store-Conditional (SC) instructions. The standard
                   implementation gives more correct behaviour, but can cause
                   indefinite looping on certain processor implementations
                   that are intolerant of extra memory references between LL
                   and SC. So far this is known only to happen on Cavium 3
                   cores. You should not need to use this flag, since the
                   relevant cores are detected at startup and the alternative
                   implementation is automatically enabled if necessary.
                   There is no equivalent anti-flag: you cannot force-disable
                   the alternative implementation, if it is automatically
                   enabled. The underlying problem exists because the
                   "standard" implementation of LL and SC is done by copying
                   through LL and SC instructions into the instrumented code.
                   However, tools may insert extra instrumentation memory
                   references in between the LL and SC instructions. These
                   memory references are not present in the original
                   uninstrumented code, and their presence in the
                   instrumented code can cause the SC instructions to
                   persistently fail, leading to indefinite looping in LL-SC
                   blocks. The alternative implementation gives correct
                   behaviour of LL and SC instructions between threads in a
                   process, up to and including the ABA scenario. It also
                   gives correct behaviour between a Valgrinded thread and a
                   non-Valgrinded thread running in a different process, that
                   communicate via shared memory, but only up to and
                   including correct CAS behaviour -- in this case the ABA
                   scenario may not be correctly handled.
    
           **--scheduling-quantum= <number> [default: 100000]**
               The **--scheduling-quantum** option controls the maximum number of
               basic blocks executed by a thread before releasing the lock
               used by Valgrind to serialise thread execution. Smaller values
               give finer interleaving but increases the scheduling overhead.
               Finer interleaving can be useful to reproduce race conditions
               with helgrind or DRD. For more details about the Valgrind
               thread serialisation scheme and its impact on performance and
               thread scheduling, see Scheduling and Multi-Thread
               Performance.
    
           **--fair-sched= <no|yes|try> [default: no]**
               The **--fair-sched** option controls the locking mechanism used by
               Valgrind to serialise thread execution. The locking mechanism
               controls the way the threads are scheduled, and different
               settings give different trade-offs between fairness and
               performance. For more details about the Valgrind thread
               serialisation scheme and its impact on performance and thread
               scheduling, see Scheduling and Multi-Thread Performance.
    
               •   The value **--fair-sched=yes** activates a fair scheduler. In
                   short, if multiple threads are ready to run, the threads
                   will be scheduled in a round robin fashion. This mechanism
                   is not available on all platforms or Linux versions. If
                   not available, using **--fair-sched=yes** will cause Valgrind
                   to terminate with an error.
    
                   You may find this setting improves overall responsiveness
                   if you are running an interactive multithreaded program,
                   for example a web browser, on Valgrind.
    
               •   The value **--fair-sched=try** activates fair scheduling if
                   available on the platform. Otherwise, it will
                   automatically fall back to **--fair-sched=no**.
    
               •   The value **--fair-sched=no** activates a scheduler which does
                   not guarantee fairness between threads ready to run, but
                   which in general gives the highest performance.
    
           **--kernel-variant=variant1,variant2,...**
               Handle system calls and ioctls arising from minor variants of
               the default kernel for this platform. This is useful for
               running on hacked kernels or with kernel modules which support
               nonstandard ioctls, for example. Use with caution. If you
               don't understand what this option does then you almost
               certainly don't need it. Currently known variants are:
    
               •   **bproc** : support the **sys_broc** system call on x86. This is
                   for running on BProc, which is a minor variant of standard
                   Linux which is sometimes used for building clusters.
    
               •   **android-no-hw-tls** : some versions of the Android emulator
                   for ARM do not provide a hardware TLS (thread-local state)
                   register, and Valgrind crashes at startup. Use this
                   variant to select software support for TLS.
    
               •   **android-gpu-sgx5xx** : use this to support handling of
                   proprietary ioctls for the PowerVR SGX 5XX series of GPUs
                   on Android devices. Failure to select this does not cause
                   stability problems, but may cause Memcheck to report false
                   errors after the program performs GPU-specific ioctls.
    
               •   **android-gpu-adreno3xx** : similarly, use this to support
                   handling of proprietary ioctls for the Qualcomm Adreno 3XX
                   series of GPUs on Android devices.
    
           **--merge-recursive-frames= <number> [default: 0]**
               Some recursive algorithms, for example balanced binary tree
               implementations, create many different stack traces, each
               containing cycles of calls. A cycle is defined as two
               identical program counter values separated by zero or more
               other program counter values. Valgrind may then use a lot of
               memory to store all these stack traces. This is a poor use of
               memory considering that such stack traces contain repeated
               uninteresting recursive calls instead of more interesting
               information such as the function that has initiated the
               recursive call.
    
               The option **--merge-recursive-frames= <number> **instructs
               Valgrind to detect and merge recursive call cycles having a
               size of up to **< number> **frames. When such a cycle is detected,
               Valgrind records the cycle in the stack trace as a unique
               program counter.
    
               The value 0 (the default) causes no recursive call merging. A
               value of 1 will cause stack traces of simple recursive
               algorithms (for example, a factorial implementation) to be
               collapsed. A value of 2 will usually be needed to collapse
               stack traces produced by recursive algorithms such as binary
               trees, quick sort, etc. Higher values might be needed for more
               complex recursive algorithms.
    
               Note: recursive calls are detected by analysis of program
               counter values. They are not detected by looking at function
               names.
    
           **--num-transtab-sectors= <number> [default: 6 for Android platforms,**
           **16 for all others]**
               Valgrind translates and instruments your program's machine
               code in small fragments (basic blocks). The translations are
               stored in a translation cache that is divided into a number of
               sections (sectors). If the cache is full, the sector
               containing the oldest translations is emptied and reused. If
               these old translations are needed again, Valgrind must
               re-translate and re-instrument the corresponding machine code,
               which is expensive. If the "executed instructions" working set
               of a program is big, increasing the number of sectors may
               improve performance by reducing the number of re-translations
               needed. Sectors are allocated on demand. Once allocated, a
               sector can never be freed, and occupies considerable space,
               depending on the tool and the value of
               **--avg-transtab-entry-size**(about 40 MB per sector for
               Memcheck). Use the option **--stats=yes** to obtain precise
               information about the memory used by a sector and the
               allocation and recycling of sectors.
    
           **--avg-transtab-entry-size= <number> [default: 0, meaning use tool**
           **provided default]**
               Average size of translated basic block. This average size is
               used to dimension the size of a sector. Each tool provides a
               default value to be used. If this default value is too small,
               the translation sectors will become full too quickly. If this
               default value is too big, a significant part of the
               translation sector memory will be unused. Note that the
               average size of a basic block translation depends on the tool,
               and might depend on tool options. For example, the memcheck
               option **--track-origins=yes** increases the size of the basic
               block translations. Use **--avg-transtab-entry-size** to tune the
               size of the sectors, either to gain memory or to avoid too
               many retranslations.
    
           **--aspace-minaddr= <address> [default: depends on the platform]**
               To avoid potential conflicts with some system libraries,
               Valgrind does not use the address space below **--aspace-minaddr**
               value, keeping it reserved in case a library specifically
               requests memory in this region. So, some "pessimistic" value
               is guessed by Valgrind depending on the platform. On linux, by
               default, Valgrind avoids using the first 64MB even if
               typically there is no conflict in this complete zone. You can
               use the option **--aspace-minaddr** to have your memory hungry
               application benefitting from more of this lower memory. On the
               other hand, if you encounter a conflict, increasing
               aspace-minaddr value might solve it. Conflicts will typically
               manifest themselves with mmap failures in the low range of the
               address space. The provided address must be page aligned and
               must be equal or bigger to 0x1000 (4KB). To find the default
               value on your platform, do something such as valgrind -d -d
               date 2>&1 | grep -i minaddr. Values lower than 0x10000 (64KB)
               are known to create problems on some distributions.
    
           **--valgrind-stacksize= <number> [default: 1MB]**
               For each thread, Valgrind needs its own 'private' stack. The
               default size for these stacks is largely dimensioned, and so
               should be sufficient in most cases. In case the size is too
               small, Valgrind will segfault. Before segfaulting, a warning
               might be produced by Valgrind when approaching the limit.
    
               Use the option **--valgrind-stacksize** if such an (unlikely)
               warning is produced, or Valgrind dies due to a segmentation
               violation. Such segmentation violations have been seen when
               demangling huge C++ symbols.
    
               If your application uses many threads and needs a lot of
               memory, you can gain some memory by reducing the size of these
               Valgrind stacks using the option **--valgrind-stacksize**.
    
           **--show-emwarns= <yes|no> [default: no]**
               When enabled, Valgrind will emit warnings about its CPU
               emulation in certain cases. These are usually not interesting.
    
           **--require-text-symbol=:sonamepatt:fnnamepatt**
               When a shared object whose soname matches _sonamepatt_ is loaded
               into the process, examine all the text symbols it exports. If
               none of those match _fnnamepatt_ , print an error message and
               abandon the run. This makes it possible to ensure that the run
               does not continue unless a given shared object contains a
               particular function name.
    
               Both _sonamepatt_ and _fnnamepatt_ can be written using the usual
               _?_  and _*_ wildcards. For example: _":*libc.so*:foo?bar"_. You may
               use characters other than a colon to separate the two
               patterns. It is only important that the first character and
               the separator character are the same. For example, the above
               example could also be written _"Q*libc.so*Qfoo?bar"_. Multiple
                _--require-text-symbol_ flags are allowed, in which case shared
               objects that are loaded into the process will be checked
               against all of them.
    
               The purpose of this is to support reliable usage of marked-up
               libraries. For example, suppose we have a version of GCC's
               _libgomp.so_ which has been marked up with annotations to
               support Helgrind. It is only too easy and confusing to load
               the wrong, un-annotated _libgomp.so_ into the application. So
               the idea is: add a text symbol in the marked-up library, for
               example _annotated_for_helgrind_3_6_ , and then give the flag
               _--require-text-symbol=:*libgomp*so*:annotated_for_helgrind_3_6_
               so that when _libgomp.so_ is loaded, Valgrind scans its symbol
               table, and if the symbol isn't present the run is aborted,
               rather than continuing silently with the un-marked-up library.
               Note that you should put the entire flag in quotes to stop
               shells expanding up the _*_ and _?_  wildcards.
    
           **--soname-synonyms=syn1=pattern1,syn2=pattern2,...**
               When a shared library is loaded, Valgrind checks for functions
               in the library that must be replaced or wrapped. For example,
               Memcheck replaces some string and memory functions (strchr,
               strlen, strcpy, memchr, memcpy, memmove, etc.) with its own
               versions. Such replacements are normally done only in shared
               libraries whose soname matches a predefined soname pattern
               (e.g.  _libc.so*_ on linux). By default, no replacement is done
               for a statically linked binary or for alternative libraries,
               except for the allocation functions (malloc, free, calloc,
               memalign, realloc, operator new, operator delete, etc.) Such
               allocation functions are intercepted by default in any shared
               library or in the executable if they are exported as global
               symbols. This means that if a replacement allocation library
               such as tcmalloc is found, its functions are also intercepted
               by default. In some cases, the replacements allow
               **--soname-synonyms** to specify one additional synonym pattern,
               giving flexibility in the replacement. Or to prevent
               interception of all public allocation symbols.
    
               Currently, this flexibility is only allowed for the malloc
               related functions, using the synonym _somalloc_. This synonym is
               usable for all tools doing standard replacement of malloc
               related functions (e.g. memcheck, helgrind, drd, massif,
               dhat).
    
               •   Alternate malloc library: to replace the malloc related
                   functions in a specific alternate library with soname
                   _mymalloclib.so_ (and not in any others), give the option
                   **--soname-synonyms=somalloc=mymalloclib.so**. A pattern can
                   be used to match multiple libraries sonames. For example,
                   **--soname-synonyms=somalloc=*tcmalloc*** will match the
                   soname of all variants of the tcmalloc library (native,
                   debug, profiled, ... tcmalloc variants).
    
                   Note: the soname of a elf shared library can be retrieved
                   using the readelf utility.
    
               •   Replacements in a statically linked library are done by
                   using the _NONE_ pattern. For example, if you link with
                   _libtcmalloc.a_ , and only want to intercept the malloc
                   related functions in the executable (and standard
                   libraries) themselves, but not any other shared libraries,
                   you can give the option **--soname-synonyms=somalloc=NONE**.
                   Note that a NONE pattern will match the main executable
                   and any shared library having no soname.
    
               •   To only intercept allocation symbols in the default system
                   libraries, but not in any other shared library or the
                   executable defining public malloc or operator new related
                   functions use a non-existing library name like
                   **--soname-synonyms=somalloc=nouserintercepts**(where
                   _nouserintercepts_ can be any non-existing library name).
    
               •   Shared library of the dynamic (runtime) linker is excluded
                   from searching for global public symbols, such as those
                   for the malloc related functions (identified by _somalloc_
                   synonym).
    
           **--progress-interval= <number> [default: 0, meaning 'disabled']**
               This is an enhancement to Valgrind's debugging output. It is
               unlikely to be of interest to end users.
    
               When _number_ is set to a non-zero value, Valgrind will print a
               one-line progress summary every _number_ seconds. Valid settings
               for _number_ are between 0 and 3600 inclusive. Here's some
               example output with _number_ set to 10:
    
                   PROGRESS: U 110s, W 113s, 97.3% CPU, EvC 414.79M, TIn 616.7k, TOut 0.5k, #thr 67
                   PROGRESS: U 120s, W 124s, 96.8% CPU, EvC 505.27M, TIn 636.6k, TOut 3.0k, #thr 64
                   PROGRESS: U 130s, W 134s, 97.0% CPU, EvC 574.90M, TIn 657.5k, TOut 3.0k, #thr 63
    
               Each line shows:
    
               •   _U_ : total user time
    
               •   _W_ : total wallclock time
    
               •   _CPU_ : overall average cpu use
    
               •   _EvC_ : number of event checks. An event check is a backwards
                   branch in the simulated program, so this is a measure of
                   forward progress of the program
    
               •   _TIn_ : number of code blocks instrumented by the JIT
    
               •   _TOut_ : number of instrumented code blocks that have been
                   thrown away
    
               •   _#thr_ : number of threads in the program
    
               From the progress of these, it is possible to observe:
    
               •   when the program is compute bound (_TIn_ rises slowly, _EvC_
                   rises rapidly)
    
               •   when the program is in a spinloop (_TIn_ /_TOut_ fixed, _EvC_
                   rises rapidly)
    
               •   when the program is JIT-bound (_TIn_ rises rapidly)
    
               •   when the program is rapidly discarding code (_TOut_ rises
                   rapidly)
    
               •   when the program is about to achieve some expected state
                   (_EvC_ arrives at some value you expect)
    
               •   when the program is idling (_U_ rises more slowly than _W_)
    


## DEBUGGING VALGRIND OPTIONS



           There are also some options for debugging Valgrind itself. You
           shouldn't need to use them in the normal run of things. If you
           wish to see the list, use the **--help-debug** option.
    


## MEMCHECK OPTIONS



           **--leak-check= <no|summary|yes|full> [default: summary]**
               When enabled, search for memory leaks when the client program
               finishes. If set to _summary_ , it says how many leaks occurred.
               If set to _full_ or _yes_ , each individual leak will be shown in
               detail and/or counted as an error, as specified by the options
               **--show-leak-kinds** and **--errors-for-leak-kinds**.
    
               If _--xml=yes_ is given, memcheck will automatically use the
               value _--leak-check=full_. You can use **--show-leak-kinds=none** to
               reduce the size of the xml output if you are not interested in
               the leak results.
    
           **--leak-resolution= <low|med|high> [default: high]**
               When doing leak checking, determines how willing Memcheck is
               to consider different backtraces to be the same for the
               purposes of merging multiple leaks into a single leak report.
               When set to _low_ , only the first two entries need match. When
               _med_ , four entries have to match. When _high_ , all entries need
               to match.
    
               For hardcore leak debugging, you probably want to use
               **--leak-resolution=high** together with **--num-callers=40** or some
               such large number.
    
               Note that the **--leak-resolution** setting does not affect
               Memcheck's ability to find leaks. It only changes how the
               results are presented.
    
           **--show-leak-kinds= <set> [default: definite,possible]**
               Specifies the leak kinds to show in a _full_ leak search, in one
               of the following ways:
    
               •   a comma separated list of one or more of **definite indirect**
                   **possible reachable**.
    
               •   **all** to specify the complete set (all leak kinds). It is
                   equivalent to
                   **--show-leak-kinds=definite,indirect,possible,reachable**.
    
               •   **none** for the empty set.
    
           **--errors-for-leak-kinds= <set> [default: definite,possible]**
               Specifies the leak kinds to count as errors in a _full_ leak
               search. The **< set> **is specified similarly to **--show-leak-kinds**
    
           **--leak-check-heuristics= <set> [default: all]**
               Specifies the set of leak check heuristics to be used during
               leak searches. The heuristics control which interior pointers
               to a block cause it to be considered as reachable. The
               heuristic set is specified in one of the following ways:
    
               •   a comma separated list of one or more of **stdstring**
                   **length64 newarray multipleinheritance**.
    
               •   **all** to activate the complete set of heuristics. It is
                   equivalent to
                   **--leak-check-heuristics=stdstring,length64,newarray,multipleinheritance**.
    
               •   **none** for the empty set.
    
               Note that these heuristics are dependent on the layout of the
               objects produced by the C++ compiler. They have been tested
               with some gcc versions (e.g. 4.4 and 4.7). They might not work
               properly with other C++ compilers.
    
           **--show-reachable= <yes|no> **, **--show-possibly-lost= <yes|no>**
               These options provide an alternative way to specify the leak
               kinds to show:
    
               •   **--show-reachable=no --show-possibly-lost=yes** is equivalent
                   to **--show-leak-kinds=definite,possible**.
    
               •   **--show-reachable=no --show-possibly-lost=no** is equivalent
                   to **--show-leak-kinds=definite**.
    
               •   **--show-reachable=yes** is equivalent to
                   **--show-leak-kinds=all**.
    
               Note that **--show-possibly-lost=no** has no effect if
               **--show-reachable=yes** is specified.
    
           **--xtree-leak= <no|yes> [no]**
               If set to yes, the results for the leak search done at exit
               will be output in a 'Callgrind Format' execution tree file.
               Note that this automatically sets the options
               **--leak-check=full** and **--show-leak-kinds=all** , to allow xtree
               visualisation tools such as kcachegrind to select what kind to
               leak to visualize. The produced file will contain the
               following events:
    
               •   **RB** : Reachable Bytes
    
               •   **PB** : Possibly lost Bytes
    
               •   **IB** : Indirectly lost Bytes
    
               •   **DB** : Definitely lost Bytes (direct plus indirect)
    
               •   **DIB** : Definitely Indirectly lost Bytes (subset of DB)
    
               •   **RBk** : reachable Blocks
    
               •   **PBk** : Possibly lost Blocks
    
               •   **IBk** : Indirectly lost Blocks
    
               •   **DBk** : Definitely lost Blocks
    
               The increase or decrease for all events above will also be
               output in the file to provide the delta (increase or decrease)
               between 2 successive leak searches. For example, **iRB** is the
               increase of the **RB** event, **dPBk** is the decrease of **PBk** event.
               The values for the increase and decrease events will be zero
               for the first leak search done.
    
               See Execution Trees for a detailed explanation about execution
               trees.
    
           **--xtree-leak-file= <filename> [default: xtleak.kcg.%p]**
               Specifies that Valgrind should produce the xtree leak report
               in the specified file. Any **%p** , **%q** or **%n** sequences appearing in
               the filename are expanded in exactly the same way as they are
               for **--log-file**. See the description of --log-file for details.
    
               See Execution Trees for a detailed explanation about execution
               trees formats.
    
           **--undef-value-errors= <yes|no> [default: yes]**
               Controls whether Memcheck reports uses of undefined value
               errors. Set this to _no_ if you don't want to see undefined
               value errors. It also has the side effect of speeding up
               Memcheck somewhat. AddrCheck (removed in Valgrind 3.1.0)
               functioned like Memcheck with **--undef-value-errors=no**.
    
           **--track-origins= <yes|no> [default: no]**
               Controls whether Memcheck tracks the origin of uninitialised
               values. By default, it does not, which means that although it
               can tell you that an uninitialised value is being used in a
               dangerous way, it cannot tell you where the uninitialised
               value came from. This often makes it difficult to track down
               the root problem.
    
               When set to _yes_ , Memcheck keeps track of the origins of all
               uninitialised values. Then, when an uninitialised value error
               is reported, Memcheck will try to show the origin of the
               value. An origin can be one of the following four places: a
               heap block, a stack allocation, a client request, or
               miscellaneous other sources (eg, a call to _brk_).
    
               For uninitialised values originating from a heap block,
               Memcheck shows where the block was allocated. For
               uninitialised values originating from a stack allocation,
               Memcheck can tell you which function allocated the value, but
               no more than that -- typically it shows you the source
               location of the opening brace of the function. So you should
               carefully check that all of the function's local variables are
               initialised properly.
    
               Performance overhead: origin tracking is expensive. It halves
               Memcheck's speed and increases memory use by a minimum of
               100MB, and possibly more. Nevertheless it can drastically
               reduce the effort required to identify the root cause of
               uninitialised value errors, and so is often a programmer
               productivity win, despite running more slowly.
    
               Accuracy: Memcheck tracks origins quite accurately. To avoid
               very large space and time overheads, some approximations are
               made. It is possible, although unlikely, that Memcheck will
               report an incorrect origin, or not be able to identify any
               origin.
    
               Note that the combination **--track-origins=yes** and
               **--undef-value-errors=no** is nonsensical. Memcheck checks for
               and rejects this combination at startup.
    
           **--partial-loads-ok= <yes|no> [default: yes]**
               Controls how Memcheck handles 32-, 64-, 128- and 256-bit
               naturally aligned loads from addresses for which some bytes
               are addressable and others are not. When _yes_ , such loads do
               not produce an address error. Instead, loaded bytes
               originating from illegal addresses are marked as
               uninitialised, and those corresponding to legal addresses are
               handled in the normal way.
    
               When _no_ , loads from partially invalid addresses are treated
               the same as loads from completely invalid addresses: an
               illegal-address error is issued, and the resulting bytes are
               marked as initialised.
    
               Note that code that behaves in this way is in violation of the
               ISO C/C++ standards, and should be considered broken. If at
               all possible, such code should be fixed.
    
           **--expensive-definedness-checks= <no|auto|yes> [default: auto]**
               Controls whether Memcheck should employ more precise but also
               more expensive (time consuming) instrumentation when checking
               the definedness of certain values. In particular, this affects
               the instrumentation of integer adds, subtracts and equality
               comparisons.
    
               Selecting **--expensive-definedness-checks=yes** causes Memcheck
               to use the most accurate analysis possible. This minimises
               false error rates but can cause up to 30% performance
               degradation.
    
               Selecting **--expensive-definedness-checks=no** causes Memcheck to
               use the cheapest instrumentation possible. This maximises
               performance but will normally give an unusably high false
               error rate.
    
               The default setting, **--expensive-definedness-checks=auto** , is
               strongly recommended. This causes Memcheck to use the minimum
               of expensive instrumentation needed to achieve the same false
               error rate as **--expensive-definedness-checks=yes**. It also
               enables an instrumentation-time analysis pass which aims to
               further reduce the costs of accurate instrumentation. Overall,
               the performance loss is generally around 5% relative to
               **--expensive-definedness-checks=no** , although this is strongly
               workload dependent. Note that the exact instrumentation
               settings in this mode are architecture dependent.
    
           **--keep-stacktraces=alloc|free|alloc-and-free|alloc-then-free|none**
           **[default: alloc-and-free]**
               Controls which stack trace(s) to keep for malloc'd and/or
               free'd blocks.
    
               With _alloc-then-free_ , a stack trace is recorded at allocation
               time, and is associated with the block. When the block is
               freed, a second stack trace is recorded, and this replaces the
               allocation stack trace. As a result, any "use after free"
               errors relating to this block can only show a stack trace for
               where the block was freed.
    
               With _alloc-and-free_ , both allocation and the deallocation
               stack traces for the block are stored. Hence a "use after
               free" error will show both, which may make the error easier to
               diagnose. Compared to _alloc-then-free_ , this setting slightly
               increases Valgrind's memory use as the block contains two
               references instead of one.
    
               With _alloc_ , only the allocation stack trace is recorded (and
               reported). With _free_ , only the deallocation stack trace is
               recorded (and reported). These values somewhat decrease
               Valgrind's memory and cpu usage. They can be useful depending
               on the error types you are searching for and the level of
               detail you need to analyse them. For example, if you are only
               interested in memory leak errors, it is sufficient to record
               the allocation stack traces.
    
               With _none_ , no stack traces are recorded for malloc and free
               operations. If your program allocates a lot of blocks and/or
               allocates/frees from many different stack traces, this can
               significantly decrease cpu and/or memory required. Of course,
               few details will be reported for errors related to heap
               blocks.
    
               Note that once a stack trace is recorded, Valgrind keeps the
               stack trace in memory even if it is not referenced by any
               block. Some programs (for example, recursive algorithms) can
               generate a huge number of stack traces. If Valgrind uses too
               much memory in such circumstances, you can reduce the memory
               required with the options _--keep-stacktraces_ and/or by using a
               smaller value for the option _--num-callers_.
    
               If you want to use --xtree-memory=full memory profiling (see
               Execution Trees), then you cannot specify
               _--keep-stacktraces=free_ or _--keep-stacktraces=none_.
    
           **--freelist-vol= <number> [default: 20000000]**
               When the client program releases memory using **free**(in C) or
               delete (C++), that memory is not immediately made available
               for re-allocation. Instead, it is marked inaccessible and
               placed in a queue of freed blocks. The purpose is to defer as
               long as possible the point at which freed-up memory comes back
               into circulation. This increases the chance that Memcheck will
               be able to detect invalid accesses to blocks for some
               significant period of time after they have been freed.
    
               This option specifies the maximum total size, in bytes, of the
               blocks in the queue. The default value is twenty million
               bytes. Increasing this increases the total amount of memory
               used by Memcheck but may detect invalid uses of freed blocks
               which would otherwise go undetected.
    
           **--freelist-big-blocks= <number> [default: 1000000]**
               When making blocks from the queue of freed blocks available
               for re-allocation, Memcheck will in priority re-circulate the
               blocks with a size greater or equal to **--freelist-big-blocks**.
               This ensures that freeing big blocks (in particular freeing
               blocks bigger than **--freelist-vol**) does not immediately lead
               to a re-circulation of all (or a lot of) the small blocks in
               the free list. In other words, this option increases the
               likelihood to discover dangling pointers for the "small"
               blocks, even when big blocks are freed.
    
               Setting a value of 0 means that all the blocks are
               re-circulated in a FIFO order.
    
           **--workaround-gcc296-bugs= <yes|no> [default: no]**
               When enabled, assume that reads and writes some small distance
               below the stack pointer are due to bugs in GCC 2.96, and does
               not report them. The "small distance" is 256 bytes by default.
               Note that GCC 2.96 is the default compiler on some ancient
               Linux distributions (RedHat 7.X) and so you may need to use
               this option. Do not use it if you do not have to, as it can
               cause real errors to be overlooked. A better alternative is to
               use a more recent GCC in which this bug is fixed.
    
               You may also need to use this option when working with GCC 3.X
               or 4.X on 32-bit PowerPC Linux. This is because GCC generates
               code which occasionally accesses below the stack pointer,
               particularly for floating-point to/from integer conversions.
               This is in violation of the 32-bit PowerPC ELF specification,
               which makes no provision for locations below the stack pointer
               to be accessible.
    
               This option is deprecated as of version 3.12 and may be
               removed from future versions. You should instead use
               **--ignore-range-below-sp** to specify the exact range of offsets
               below the stack pointer that should be ignored. A suitable
               equivalent is **--ignore-range-below-sp=1024-1**.
    
           **--ignore-range-below-sp= <number>-<number>**
               This is a more general replacement for the deprecated
               **--workaround-gcc296-bugs** option. When specified, it causes
               Memcheck not to report errors for accesses at the specified
               offsets below the stack pointer. The two offsets must be
               positive decimal numbers and -- somewhat counterintuitively --
               the first one must be larger, in order to imply a
               non-wraparound address range to ignore. For example, to ignore
               4 byte accesses at 8192 bytes below the stack pointer, use
               **--ignore-range-below-sp=8192-8189**. Only one range may be
               specified.
    
           **--show-mismatched-frees= <yes|no> [default: yes]**
               When enabled, Memcheck checks that heap blocks are deallocated
               using a function that matches the allocating function. That
               is, it expects _free_ to be used to deallocate blocks allocated
               by _malloc_ , _delete_ for blocks allocated by _new_ , and _delete[]_
               for blocks allocated by _new[]_. If a mismatch is detected, an
               error is reported. This is in general important because in
               some environments, freeing with a non-matching function can
               cause crashes.
    
               There is however a scenario where such mismatches cannot be
               avoided. That is when the user provides implementations of
               _new_ /_new[]_ that call _malloc_ and of _delete_ /_delete[]_ that call
               _free_ , and these functions are asymmetrically inlined. For
               example, imagine that _delete[]_ is inlined but _new[]_ is not.
               The result is that Memcheck "sees" all _delete[]_ calls as
               direct calls to _free_ , even when the program source contains no
               mismatched calls.
    
               This causes a lot of confusing and irrelevant error reports.
               _--show-mismatched-frees=no_ disables these checks. It is not
               generally advisable to disable them, though, because you may
               miss real errors as a result.
    
           **--show-realloc-size-zero= <yes|no> [default: yes]**
               When enabled, Memcheck checks for uses of _realloc_ with a size
               of zero. This usage of _realloc_ is unsafe since it is not
               portable. On some systems it will behave like _free_. On other
               systems it will either do nothing or else behave like a call
               to _free_ followed by a call to _malloc_ with a size of zero.
    
           **--ignore-ranges=0xPP-0xQQ[,0xRR-0xSS]**
               Any ranges listed in this option (and multiple ranges can be
               specified, separated by commas) will be ignored by Memcheck's
               addressability checking.
    
           **--malloc-fill= <hexnumber>**
               Fills blocks allocated by malloc, new, etc, but not by calloc,
               with the specified byte. This can be useful when trying to
               shake out obscure memory corruption problems. The allocated
               area is still regarded by Memcheck as undefined -- this option
               only affects its contents. Note that **--malloc-fill** does not
               affect a block of memory when it is used as argument to client
               requests VALGRIND_MEMPOOL_ALLOC or VALGRIND_MALLOCLIKE_BLOCK.
    
           **--free-fill= <hexnumber>**
               Fills blocks freed by free, delete, etc, with the specified
               byte value. This can be useful when trying to shake out
               obscure memory corruption problems. The freed area is still
               regarded by Memcheck as not valid for access -- this option
               only affects its contents. Note that **--free-fill** does not
               affect a block of memory when it is used as argument to client
               requests VALGRIND_MEMPOOL_FREE or VALGRIND_FREELIKE_BLOCK.
    


## CACHEGRIND OPTIONS



           **--cachegrind-out-file= <file>**
               Write the Cachegrind output file to file rather than to the
               default output file, cachegrind.out.<pid>. The **%p** and **%q**
               format specifiers can be used to embed the process ID and/or
               the contents of an environment variable in the name, as is the
               case for the core option **--log-file**.
    
           **--cache-sim=no|yes [no]**
               Enables or disables collection of cache access and miss
               counts.
    
           **--branch-sim=no|yes [no]**
               Enables or disables collection of branch instruction and
               misprediction counts.
    
           **--instr-at-start=no|yes [yes]**
               Enables or disables instrumentation at the start of execution.
               Use this in combination with CACHEGRIND_START_INSTRUMENTATION
               and CACHEGRIND_STOP_INSTRUMENTATION to measure only part of a
               client program's execution.
    
           **--I1= <size>,<associativity>,<line size>**
               Specify the size, associativity and line size of the level 1
               instruction cache. Only useful with **--cache-sim=yes**.
    
           **--D1= <size>,<associativity>,<line size>**
               Specify the size, associativity and line size of the level 1
               data cache. Only useful with **--cache-sim=yes**.
    
           **--LL= <size>,<associativity>,<line size>**
               Specify the size, associativity and line size of the
               last-level cache. Only useful with **--cache-sim=yes**.
    


## CALLGRIND OPTIONS



           **--callgrind-out-file= <file>**
               Write the profile data to file rather than to the default
               output file, callgrind.out.<pid>. The **%p** and **%q** format
               specifiers can be used to embed the process ID and/or the
               contents of an environment variable in the name, as is the
               case for the core option **--log-file**. When multiple dumps are
               made, the file name is modified further; see below.
    
           **--dump-line= <no|yes> [default: yes]**
               This specifies that event counting should be performed at
               source line granularity. This allows source annotation for
               sources which are compiled with debug information (**-g**).
    
           **--dump-instr= <no|yes> [default: no]**
               This specifies that event counting should be performed at
               per-instruction granularity. This allows for assembly code
               annotation. Currently the results can only be displayed by
               KCachegrind.
    
           **--compress-strings= <no|yes> [default: yes]**
               This option influences the output format of the profile data.
               It specifies whether strings (file and function names) should
               be identified by numbers. This shrinks the file, but makes it
               more difficult for humans to read (which is not recommended in
               any case).
    
           **--compress-pos= <no|yes> [default: yes]**
               This option influences the output format of the profile data.
               It specifies whether numerical positions are always specified
               as absolute values or are allowed to be relative to previous
               numbers. This shrinks the file size.
    
           **--combine-dumps= <no|yes> [default: no]**
               When enabled, when multiple profile data parts are to be
               generated these parts are appended to the same output file.
               Not recommended.
    
           **--dump-every-bb= <count> [default: 0, never]**
               Dump profile data every **count** basic blocks. Whether a dump is
               needed is only checked when Valgrind's internal scheduler is
               run. Therefore, the minimum setting useful is about 100000.
               The count is a 64-bit value to make long dump periods
               possible.
    
           **--dump-before= <function>**
               Dump when entering **function**.
    
           **--zero-before= <function>**
               Zero all costs when entering **function**.
    
           **--dump-after= <function>**
               Dump when leaving **function**.
    
           **--instr-atstart= <yes|no> [default: yes]**
               Specify if you want Callgrind to start simulation and
               profiling from the beginning of the program. When set to no,
               Callgrind will not be able to collect any information,
               including calls, but it will have at most a slowdown of around
               4, which is the minimum Valgrind overhead. Instrumentation can
               be interactively enabled via callgrind_control -i on.
    
               Note that the resulting call graph will most probably not
               contain **main** , but will contain all the functions executed
               after instrumentation was enabled. Instrumentation can also be
               programmatically enabled/disabled. See the Callgrind include
               file callgrind.h for the macro you have to use in your source
               code.
    
               For cache simulation, results will be less accurate when
               switching on instrumentation later in the program run, as the
               simulator starts with an empty cache at that moment. Switch on
               event collection later to cope with this error.
    
           **--collect-atstart= <yes|no> [default: yes]**
               Specify whether event collection is enabled at beginning of
               the profile run.
    
               To only look at parts of your program, you have two
               possibilities:
    
                1. Zero event counters before entering the program part you
                   want to profile, and dump the event counters to a file
                   after leaving that program part.
    
                2. Switch on/off collection state as needed to only see event
                   counters happening while inside of the program part you
                   want to profile.
    
               The second option can be used if the program part you want to
               profile is called many times. Option 1, i.e. creating a lot of
               dumps is not practical here.
    
               Collection state can be toggled at entry and exit of a given
               function with the option **--toggle-collect**. If you use this
               option, collection state should be disabled at the beginning.
               Note that the specification of **--toggle-collect** implicitly
               sets **--collect-state=no**.
    
               Collection state can be toggled also by inserting the client
               request CALLGRIND_TOGGLE_COLLECT ; at the needed code
               positions.
    
           **--toggle-collect= <function>**
               Toggle collection on entry/exit of **function**.
    
           **--collect-jumps= <no|yes> [default: no]**
               This specifies whether information for (conditional) jumps
               should be collected. As above, callgrind_annotate currently is
               not able to show you the data. You have to use KCachegrind to
               get jump arrows in the annotated code.
    
           **--collect-systime= <no|yes|msec|usec|nsec> [default: no]**
               This specifies whether information for system call times
               should be collected.
    
               The value no indicates to record no system call information.
    
               The other values indicate to record the number of system calls
               done (sysCount event) and the elapsed time (sysTime event)
               spent in system calls. The --collect-systime value gives the
               unit used for sysTime : milli seconds, micro seconds or nano
               seconds. With the value nsec, callgrind also records the cpu
               time spent during system calls (sysCpuTime).
    
               The value yes is a synonym of msec. The value nsec is not
               supported on Darwin.
    
           **--collect-bus= <no|yes> [default: no]**
               This specifies whether the number of global bus events
               executed should be collected. The event type "Ge" is used for
               these events.
    
           **--cache-sim= <yes|no> [default: no]**
               Specify if you want to do full cache simulation. By default,
               only instruction read accesses will be counted ("Ir"). With
               cache simulation, further event counters are enabled: Cache
               misses on instruction reads ("I1mr"/"ILmr"), data read
               accesses ("Dr") and related cache misses ("D1mr"/"DLmr"), data
               write accesses ("Dw") and related cache misses
               ("D1mw"/"DLmw"). For more information, see Cachegrind: a cache
               and branch-prediction profiler.
    
           **--branch-sim= <yes|no> [default: no]**
               Specify if you want to do branch prediction simulation.
               Further event counters are enabled: Number of executed
               conditional branches and related predictor misses
               ("Bc"/"Bcm"), executed indirect jumps and related misses of
               the jump address predictor ("Bi"/"Bim").
    


## HELGRIND OPTIONS



           **--free-is-write=no|yes [default: no]**
               When enabled (not the default), Helgrind treats freeing of
               heap memory as if the memory was written immediately before
               the free. This exposes races where memory is referenced by one
               thread, and freed by another, but there is no observable
               synchronisation event to ensure that the reference happens
               before the free.
    
               This functionality is new in Valgrind 3.7.0, and is regarded
               as experimental. It is not enabled by default because its
               interaction with custom memory allocators is not well
               understood at present. User feedback is welcomed.
    
           **--track-lockorders=no|yes [default: yes]**
               When enabled (the default), Helgrind performs lock order
               consistency checking. For some buggy programs, the large
               number of lock order errors reported can become annoying,
               particularly if you're only interested in race errors. You may
               therefore find it helpful to disable lock order checking.
    
           **--history-level=none|approx|full [default: full]**
               **--history-level=full**(the default) causes Helgrind collects
               enough information about "old" accesses that it can produce
               two stack traces in a race report -- both the stack trace for
               the current access, and the trace for the older, conflicting
               access. To limit memory usage, "old" accesses stack traces are
               limited to a maximum of _--history-backtrace-size_ entries
               (default 8) or to **--num-callers** value if this value is
               smaller.
    
               Collecting such information is expensive in both speed and
               memory, particularly for programs that do many inter-thread
               synchronisation events (locks, unlocks, etc). Without such
               information, it is more difficult to track down the root
               causes of races. Nonetheless, you may not need it in
               situations where you just want to check for the presence or
               absence of races, for example, when doing regression testing
               of a previously race-free program.
    
               **--history-level=none** is the opposite extreme. It causes
               Helgrind not to collect any information about previous
               accesses. This can be dramatically faster than
               **--history-level=full**.
    
               **--history-level=approx** provides a compromise between these two
               extremes. It causes Helgrind to show a full trace for the
               later access, and approximate information regarding the
               earlier access. This approximate information consists of two
               stacks, and the earlier access is guaranteed to have occurred
               somewhere between program points denoted by the two stacks.
               This is not as useful as showing the exact stack for the
               previous access (as **--history-level=full** does), but it is
               better than nothing, and it is almost as fast as
               **--history-level=none**.
    
           **--history-backtrace-size= <number> [default: 8]**
               When _--history-level=full_ is selected,
               _--history-backtrace-size=number_ indicates how many entries to
               record in "old" accesses stack traces.
    
           **--delta-stacktrace=no|yes [default: yes on linux amd64/x86]**
               This flag only has any effect at **--history-level=full**.
    
               **--delta-stacktrace** configures the way Helgrind captures the
               stacktraces for the option **--history-level=full**. Such a
               stacktrace is typically needed each time a new piece of memory
               is read or written in a basic block of instructions.
    
               **--delta-stacktrace=no** causes Helgrind to compute a full
               history stacktrace from the unwind info each time a stacktrace
               is needed.
    
               **--delta-stacktrace=yes** indicates to Helgrind to derive a new
               stacktrace from the previous stacktrace, as long as there was
               no call instruction, no return instruction, or any other
               instruction changing the call stack since the previous
               stacktrace was captured. If no such instruction was executed,
               the new stacktrace can be derived from the previous stacktrace
               by just changing the top frame to the current program counter.
               This option can speed up Helgrind by 25% when using
               **--history-level=full**.
    
               The following aspects have to be considered when using
               **--delta-stacktrace=yes** :
    
               •   In some cases (for example in a function prologue), the
                   valgrind unwinder might not properly unwind the stack, due
                   to some limitations and/or due to wrong unwind info. When
                   using --delta-stacktrace=yes, the wrong stack trace
                   captured in the function prologue will be kept till the
                   next call or return.
    
               •   On the other hand, --delta-stacktrace=yes sometimes helps
                   to obtain a correct stacktrace, for example when the
                   unwind info allows a correct stacktrace to be done in the
                   beginning of the sequence, but not later on in the
                   instruction sequence.
    
               •   Determining which instructions are changing the callstack
                   is partially based on platform dependent heuristics, which
                   have to be tuned/validated specifically for the platform.
                   Also, unwinding in a function prologue must be good enough
                   to allow using --delta-stacktrace=yes. Currently, the
                   option --delta-stacktrace=yes has been reasonably
                   validated only on linux x86 32 bits and linux amd64 64
                   bits. For more details about how to validate
                   --delta-stacktrace=yes, see debug option --hg-sanity-flags
                   and the function check_cached_rcec_ok in libhb_core.c.
    
           **--conflict-cache-size=N [default: 1000000]**
               This flag only has any effect at **--history-level=full**.
    
               Information about "old" conflicting accesses is stored in a
               cache of limited size, with LRU-style management. This is
               necessary because it isn't practical to store a stack trace
               for every single memory access made by the program. Historical
               information on not recently accessed locations is periodically
               discarded, to free up space in the cache.
    
               This option controls the size of the cache, in terms of the
               number of different memory addresses for which conflicting
               access information is stored. If you find that Helgrind is
               showing race errors with only one stack instead of the
               expected two stacks, try increasing this value.
    
               The minimum value is 10,000 and the maximum is 30,000,000
               (thirty times the default value). Increasing the value by 1
               increases Helgrind's memory requirement by very roughly 100
               bytes, so the maximum value will easily eat up three extra
               gigabytes or so of memory.
    
           **--check-stack-refs=no|yes [default: yes]**
               By default Helgrind checks all data memory accesses made by
               your program. This flag enables you to skip checking for
               accesses to thread stacks (local variables). This can improve
               performance, but comes at the cost of missing races on
               stack-allocated data.
    
           **--ignore-thread-creation= <yes|no> [default: no]**
               Controls whether all activities during thread creation should
               be ignored. By default enabled only on Solaris. Solaris
               provides higher throughput, parallelism and scalability than
               other operating systems, at the cost of more fine-grained
               locking activity. This means for example that when a thread is
               created under glibc, just one big lock is used for all thread
               setup. Solaris libc uses several fine-grained locks and the
               creator thread resumes its activities as soon as possible,
               leaving for example stack and TLS setup sequence to the
               created thread. This situation confuses Helgrind as it assumes
               there is some false ordering in place between creator and
               created thread; and therefore many types of race conditions in
               the application would not be reported. To prevent such false
               ordering, this command line option is set to yes by default on
               Solaris. All activity (loads, stores, client requests) is
               therefore ignored during:
    
               •   pthread_create() call in the creator thread
    
               •   thread creation phase (stack and TLS setup) in the created
                   thread
    
               Also new memory allocated during thread creation is untracked,
               that is race reporting is suppressed there. DRD does the same
               thing implicitly. This is necessary because Solaris libc
               caches many objects and reuses them for different threads and
               that confuses Helgrind.
    


## DRD OPTIONS



           **--check-stack-var= <yes|no> [default: no]**
               Controls whether DRD detects data races on stack variables.
               Verifying stack variables is disabled by default because most
               programs do not share stack variables over threads.
    
           **--exclusive-threshold= <n> [default: off]**
               Print an error message if any mutex or writer lock has been
               held longer than the time specified in milliseconds. This
               option enables the detection of lock contention.
    
           **--join-list-vol= <n> [default: 10]**
               Data races that occur between a statement at the end of one
               thread and another thread can be missed if memory access
               information is discarded immediately after a thread has been
               joined. This option allows one to specify for how many joined
               threads memory access information should be retained.
    
            **--first-race-only= <yes|no> [default: no]**
               Whether to report only the first data race that has been
               detected on a memory location or all data races that have been
               detected on a memory location.
    
            **--free-is-write= <yes|no> [default: no]**
               Whether to report races between accessing memory and freeing
               memory. Enabling this option may cause DRD to run slightly
               slower. Notes:
    
               •   Don't enable this option when using custom memory
                   allocators that use the VG_USERREQ__MALLOCLIKE_BLOCK and
                   VG_USERREQ__FREELIKE_BLOCK because that would result in
                   false positives.
    
               •   Don't enable this option when using reference-counted
                   objects because that will result in false positives, even
                   when that code has been annotated properly with
                   ANNOTATE_HAPPENS_BEFORE and ANNOTATE_HAPPENS_AFTER. See
                   e.g. the output of the following command for an example:
                   valgrind --tool=drd --free-is-write=yes
                   drd/tests/annotate_smart_pointer.
    
            **--report-signal-unlocked= <yes|no> [default: yes]**
               Whether to report calls to **pthread_cond_signal** and
               **pthread_cond_broadcast** where the mutex associated with the
               signal through **pthread_cond_wait** or **pthread_cond_timed_wait** is
               not locked at the time the signal is sent. Sending a signal
               without holding a lock on the associated mutex is a common
               programming error which can cause subtle race conditions and
               unpredictable behavior. There exist some uncommon
               synchronization patterns however where it is safe to send a
               signal without holding a lock on the associated mutex.
    
           **--segment-merging= <yes|no> [default: yes]**
               Controls segment merging. Segment merging is an algorithm to
               limit memory usage of the data race detection algorithm.
               Disabling segment merging may improve the accuracy of the
               so-called 'other segments' displayed in race reports but can
               also trigger an out of memory error.
    
           **--segment-merging-interval= <n> [default: 10]**
               Perform segment merging only after the specified number of new
               segments have been created. This is an advanced configuration
               option that allows one to choose whether to minimize DRD's
               memory usage by choosing a low value or to let DRD run faster
               by choosing a slightly higher value. The optimal value for
               this parameter depends on the program being analyzed. The
               default value works well for most programs.
    
           **--shared-threshold= <n> [default: off]**
               Print an error message if a reader lock has been held longer
               than the specified time (in milliseconds). This option enables
               the detection of lock contention.
    
           **--show-confl-seg= <yes|no> [default: yes]**
               Show conflicting segments in race reports. Since this
               information can help to find the cause of a data race, this
               option is enabled by default. Disabling this option makes the
               output of DRD more compact.
    
           **--show-stack-usage= <yes|no> [default: no]**
               Print stack usage at thread exit time. When a program creates
               a large number of threads it becomes important to limit the
               amount of virtual memory allocated for thread stacks. This
               option makes it possible to observe how much stack memory has
               been used by each thread of the client program. Note: the DRD
               tool itself allocates some temporary data on the client thread
               stack. The space necessary for this temporary data must be
               allocated by the client program when it allocates stack
               memory, but is not included in stack usage reported by DRD.
    
           **--ignore-thread-creation= <yes|no> [default: no]**
               Controls whether all activities during thread creation should
               be ignored. By default enabled only on Solaris. Solaris
               provides higher throughput, parallelism and scalability than
               other operating systems, at the cost of more fine-grained
               locking activity. This means for example that when a thread is
               created under glibc, just one big lock is used for all thread
               setup. Solaris libc uses several fine-grained locks and the
               creator thread resumes its activities as soon as possible,
               leaving for example stack and TLS setup sequence to the
               created thread. This situation confuses DRD as it assumes
               there is some false ordering in place between creator and
               created thread; and therefore many types of race conditions in
               the application would not be reported. To prevent such false
               ordering, this command line option is set to yes by default on
               Solaris. All activity (loads, stores, client requests) is
               therefore ignored during:
    
               •   pthread_create() call in the creator thread
    
               •   thread creation phase (stack and TLS setup) in the created
                   thread
    
           **--trace-addr= <address> [default: none]**
               Trace all load and store activity for the specified address.
               This option may be specified more than once.
    
           **--ptrace-addr= <address> [default: none]**
               Trace all load and store activity for the specified address
               and keep doing that even after the memory at that address has
               been freed and reallocated.
    
           **--trace-alloc= <yes|no> [default: no]**
               Trace all memory allocations and deallocations. May produce a
               huge amount of output.
    
           **--trace-barrier= <yes|no> [default: no]**
               Trace all barrier activity.
    
           **--trace-cond= <yes|no> [default: no]**
               Trace all condition variable activity.
    
           **--trace-fork-join= <yes|no> [default: no]**
               Trace all thread creation and all thread termination events.
    
           **--trace-hb= <yes|no> [default: no]**
               Trace execution of the ANNOTATE_HAPPENS_BEFORE(),
               ANNOTATE_HAPPENS_AFTER() and ANNOTATE_HAPPENS_DONE() client
               requests.
    
           **--trace-mutex= <yes|no> [default: no]**
               Trace all mutex activity.
    
           **--trace-rwlock= <yes|no> [default: no]**
               Trace all reader-writer lock activity.
    
           **--trace-semaphore= <yes|no> [default: no]**
               Trace all semaphore activity.
    


## MASSIF OPTIONS



           **--heap= <yes|no> [default: yes]**
               Specifies whether heap profiling should be done.
    
           **--heap-admin= <size> [default: 8]**
               If heap profiling is enabled, gives the number of
               administrative bytes per block to use. This should be an
               estimate of the average, since it may vary. For example, the
               allocator used by glibc on Linux requires somewhere between 4
               to 15 bytes per block, depending on various factors. That
               allocator also requires admin space for freed blocks, but
               Massif cannot account for this.
    
           **--stacks= <yes|no> [default: no]**
               Specifies whether stack profiling should be done. This option
               slows Massif down greatly, and so is off by default. Note that
               Massif assumes that the main stack has size zero at start-up.
               This is not true, but doing otherwise accurately is difficult.
               Furthermore, starting at zero better indicates the size of the
               part of the main stack that a user program actually has
               control over.
    
               If you give at least 4 **-v** verbosity arguments, then massif
               produces a trace for each stack increase and decrease. The
               stack increase trace contains the IP address that increased
               the stack. Note that to get fully precise IP address, you must
               specify the options **-px-default=unwindregs-at-mem-access**
               **--px-file-backed=unwindregs-at-mem-access**.
    
           **--pages-as-heap= <yes|no> [default: no]**
               Tells Massif to profile memory at the page level rather than
               at the malloc'd block level. See above for details.
    
           **--depth= <number> [default: 30]**
               Maximum depth of the allocation trees recorded for detailed
               snapshots. Increasing it will make Massif run somewhat more
               slowly, use more memory, and produce bigger output files.
    
           **--alloc-fn= <name>**
               Functions specified with this option will be treated as though
               they were a heap allocation function such as **malloc**. This is
               useful for functions that are wrappers to **malloc** or **new** , which
               can fill up the allocation trees with uninteresting
               information. This option can be specified multiple times on
               the command line, to name multiple functions.
    
               Note that the named function will only be treated this way if
               it is the top entry in a stack trace, or just below another
               function treated this way. For example, if you have a function
               **malloc1** that wraps **malloc** , and **malloc2** that wraps **malloc1** ,
               just specifying **--alloc-fn=malloc2** will have no effect. You
               need to specify **--alloc-fn=malloc1** as well. This is a little
               inconvenient, but the reason is that checking for allocation
               functions is slow, and it saves a lot of time if Massif can
               stop looking through the stack trace entries as soon as it
               finds one that doesn't match rather than having to continue
               through all the entries.
    
               Note that C++ names are demangled. Note also that overloaded
               C++ names must be written in full. Single quotes may be
               necessary to prevent the shell from breaking them up. For
               example:
    
                   --alloc-fn='operator new(unsigned, std::nothrow_t const&)'
    
               Arguments of type size_t need to be replaced with unsigned
               long on 64bit platforms and unsigned on 32bit platforms.
    
               **--alloc-fn** will work with inline functions. Inline function
               names are not mangled, which means that you only need to
               provide the function name and not the argument list.
    
               **--alloc-fn** does not support wildcards.
    
           **--ignore-fn= <name>**
               Any direct heap allocation (i.e. a call to **malloc** , **new** , etc,
               or a call to a function named by an **--alloc-fn** option) that
               occurs in a function specified by this option will be ignored.
               This is mostly useful for testing purposes. This option can be
               specified multiple times on the command line, to name multiple
               functions.
    
               Any **realloc** of an ignored block will also be ignored, even if
               the **realloc** call does not occur in an ignored function. This
               avoids the possibility of negative heap sizes if ignored
               blocks are shrunk with **realloc**.
    
               The rules for writing C++ function names are the same as for
               **--alloc-fn** above.
    
           **--threshold= <m.n> [default: 1.0]**
               The significance threshold for heap allocations, as a
               percentage of total memory size. Allocation tree entries that
               account for less than this will be aggregated. Note that this
               should be specified in tandem with ms_print's option of the
               same name.
    
           **--peak-inaccuracy= <m.n> [default: 1.0]**
               Massif does not necessarily record the actual global memory
               allocation peak; by default it records a peak only when the
               global memory allocation size exceeds the previous peak by at
               least 1.0%. This is because there can be many local allocation
               peaks along the way, and doing a detailed snapshot for every
               one would be expensive and wasteful, as all but one of them
               will be later discarded. This inaccuracy can be changed (even
               to 0.0%) via this option, but Massif will run drastically
               slower as the number approaches zero.
    
           **--time-unit= <i|ms|B> [default: i]**
               The time unit used for the profiling. There are three
               possibilities: instructions executed (i), which is good for
               most cases; real (wallclock) time (ms, i.e. milliseconds),
               which is sometimes useful; and bytes allocated/deallocated on
               the heap and/or stack (B), which is useful for very short-run
               programs, and for testing purposes, because it is the most
               reproducible across different machines.
    
           **--detailed-freq= <n> [default: 10]**
               Frequency of detailed snapshots. With **--detailed-freq=1** , every
               snapshot is detailed.
    
           **--max-snapshots= <n> [default: 100]**
               The maximum number of snapshots recorded. If set to N, for all
               programs except very short-running ones, the final number of
               snapshots will be between N/2 and N.
    
           **--massif-out-file= <file> [default: massif.out.%p]**
               Write the profile data to file rather than to the default
               output file, massif.out.<pid>. The **%p** and **%q** format specifiers
               can be used to embed the process ID and/or the contents of an
               environment variable in the name, as is the case for the core
               option **--log-file**.
    


## BBV OPTIONS



           **--bb-out-file= <name> [default: bb.out.%p]**
               This option selects the name of the basic block vector file.
               The **%p** and **%q** format specifiers can be used to embed the
               process ID and/or the contents of an environment variable in
               the name, as is the case for the core option **--log-file**.
    
           **--pc-out-file= <name> [default: pc.out.%p]**
               This option selects the name of the PC file. This file holds
               program counter addresses and function name info for the
               various basic blocks. This can be used in conjunction with the
               basic block vector file to fast-forward via function names
               instead of just instruction counts. The **%p** and **%q** format
               specifiers can be used to embed the process ID and/or the
               contents of an environment variable in the name, as is the
               case for the core option **--log-file**.
    
           **--interval-size= <number> [default: 100000000]**
               This option selects the size of the interval to use. The
               default is 100 million instructions, which is a commonly used
               value. Other sizes can be used; smaller intervals can help
               programs with finer-grained phases. However smaller interval
               size can lead to accuracy issues due to warm-up effects (When
               fast-forwarding the various architectural features will be
               un-initialized, and it will take some number of instructions
               before they "warm up" to the state a full simulation would be
               at without the fast-forwarding. Large interval sizes tend to
               mitigate this.)
    
           **--instr-count-only [default: no]**
               This option tells the tool to only display instruction count
               totals, and to not generate the actual basic block vector
               file. This is useful for debugging, and for gathering
               instruction count info without generating the large basic
               block vector files.
    


## LACKEY OPTIONS



           **--basic-counts= <no|yes> [default: yes]**
               When enabled, Lackey prints the following statistics and
               information about the execution of the client program:
    
                1. The number of calls to the function specified by the
                   **--fnname** option (the default is main). If the program has
                   had its symbols stripped, the count will always be zero.
    
                2. The number of conditional branches encountered and the
                   number and proportion of those taken.
    
                3. The number of superblocks entered and completed by the
                   program. Note that due to optimisations done by the JIT,
                   this is not at all an accurate value.
    
                4. The number of guest (x86, amd64, ppc, etc.) instructions
                   and IR statements executed. IR is Valgrind's RISC-like
                   intermediate representation via which all instrumentation
                   is done.
    
                5. Ratios between some of these counts.
    
                6. The exit code of the client program.
    
           **--detailed-counts= <no|yes> [default: no]**
               When enabled, Lackey prints a table containing counts of
               loads, stores and ALU operations, differentiated by their IR
               types. The IR types are identified by their IR name ("I1",
               "I8", ... "I128", "F32", "F64", and "V128").
    
           **--trace-mem= <no|yes> [default: no]**
               When enabled, Lackey prints the size and address of almost
               every memory access made by the program. See the comments at
               the top of the file lackey/lk_main.c for details about the
               output format, how it works, and inaccuracies in the address
               trace. Note that this option produces immense amounts of
               output.
    
           **--trace-superblocks= <no|yes> [default: no]**
               When enabled, Lackey prints out the address of every
               superblock (a single entry, multiple exit, linear chunk of
               code) executed by the program. This is primarily of interest
               to Valgrind developers. See the comments at the top of the
               file lackey/lk_main.c for details about the output format.
               Note that this option produces large amounts of output.
    
           **--fnname= <name> [default: main]**
               Changes the function for which calls are counted when
               **--basic-counts=yes** is specified.
    


## DEBUGINFOD



           Valgrind supports the downloading of debuginfo files via
           debuginfod, an HTTP server for distributing ELF/DWARF debugging
           information. When a debuginfo file cannot be found locally,
           Valgrind is able to query debuginfod servers for the file using
           the file's build-id.
    
           In order to use this feature debuginfod-find must be installed and
           the $DEBUGINFOD_URLS environment variable must contain
           space-separated URLs of debuginfod servers. Valgrind does not
           support debuginfod-find verbose output that is normally enabled
           with $DEBUGINFOD_PROGRESS and $DEBUGINFOD_VERBOSE. These
           environment variables will be ignored. This feature is supported
           on Linux only.
    
           For more information regarding debuginfod, see **Elfutils**
           **Debuginfod******[1] .


## NOTES



            1. Elfutils Debuginfod
               https://sourceware.org/elfutils/Debuginfod.html
    
            2. Debugging your program using Valgrind's gdbserver and GDB
               http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.gdbserver
    
            3. vgdb
               http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.vgdb
    
            4. Valgrind monitor commands
               http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.valgrind-monitor-commands
    
            5. The Commentary
               http://www.valgrind.org/docs/manual/manual-core.html#manual-core.comment
    
            6. Scheduling and Multi-Thread Performance
               http://www.valgrind.org/docs/manual/manual-core.html#manual-core.pthreads_perf_sched
    
            7. Cachegrind: a cache and branch-prediction profiler
               http://www.valgrind.org/docs/manual/cg-manual.html
    
            8. Execution Trees
               http://www.valgrind.org/docs/manual/manual-core.html#manual-core.xtree
    


* * *