# fort77

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           fort77 — FORTRAN compiler (**FORTRAN**)
    


## SYNOPSIS



           fort77 **[** -c**] [** -g**] [** -L _directory_**]**... **[** -O _optlevel_**] [** -o _outfile_**] [** -s**]**
               **[** -w**]**_operand_...
    


## DESCRIPTION



           The _fort77_ utility is the interface to the FORTRAN compilation
           system; it shall accept the full FORTRAN-77 language defined by
           the ANSI X3.9‐1978 standard. The system conceptually consists of a
           compiler and link editor. The files referenced by _operand_ s are
           compiled and linked to produce an executable file. It is
           unspecified whether the linking occurs entirely within the
           operation of _fort77_ ; some implementations may produce objects that
           are not fully resolved until the file is executed.
    
           If the **-c** option is present, for all pathname operands of the form
           _file_**.f** , the files:
    
               $(basename _pathname_.f).o
    
           shall be created or overwritten as the result of successful
           compilation. If the **-c** option is not specified, it is unspecified
           whether such **.o** files are created or deleted for the _file_**.f**
           operands.
    
           If there are no options that prevent link editing (such as **-c**) and
           all operands compile and link without error, the resulting
           executable file shall be written into the file named by the **-o**
           option (if present) or to the file **a.out**.  The executable file
           shall be created as specified in the System Interfaces volume of
           POSIX.1‐2017, except that the file permissions shall be set to:
           S_IRWXO | S_IRWXG | S_IRWXU
    
           and that the bits specified by the _umask_ of the process shall be
           cleared.
    


## OPTIONS



           The _fort77_ utility shall conform to the Base Definitions volume of
           POSIX.1‐2017, _Section 12.2_ , _Utility Syntax Guidelines_ , except
           that:
    
            *  The **-l** _library_ operands have the format of options, but their
               position within a list of operands affects the order in which
               libraries are searched.
    
            *  The order of specifying the multiple **-L** options is
               significant.
    
            *  Conforming applications shall specify each option separately;
               that is, grouping option letters (for example, **-cg**) need not
               be recognized by all implementations.
    
           The following options shall be supported:
    
           **-c** Suppress the link-edit phase of the compilation, and do
                     not remove any object files that are produced.
    
           **-g** Produce symbolic information in the object or executable
                     files; the nature of this information is unspecified,
                     and may be modified by implementation-defined
                     interactions with other options.
    
           **-s** Produce object or executable files, or both, from which
                     symbolic and other information not required for proper
                     execution using the _exec_ family of functions defined in
                     the System Interfaces volume of POSIX.1‐2017 has been
                     removed (stripped).  If both **-g** and **-s** options are
                     present, the action taken is unspecified.
    
           **-o** _outfile_
                     Use the pathname _outfile_ , instead of the default **a.out** ,
                     for the executable file produced. If the **-o** option is
                     present with **-c** , the result is unspecified.
    
           **-L** _directory_
                     Change the algorithm of searching for the libraries
                     named in **-l** operands to look in the directory named by
                     the _directory_ pathname before looking in the usual
                     places. Directories named in **-L** options shall be
                     searched in the specified order. At least ten instances
                     of this option shall be supported in a single _fort77_
                     command invocation. If a directory specified by a **-L**
                     option contains a file named **libf.a** , the results are
                     unspecified.
    
           **-O** _optlevel_
                     Specify the level of code optimization. If the _optlevel_
                     option-argument is the digit **'0'** , all special code
                     optimizations shall be disabled. If it is the digit **'1'** ,
                     the nature of the optimization is unspecified. If the **-O**
                     option is omitted, the nature of the system's default
                     optimization is unspecified. It is unspecified whether
                     code generated in the presence of the **-O** 0 option is the
                     same as that generated when **-O** is omitted. Other
                     _optlevel_ values may be supported.
    
           **-w** Suppress warnings.
    
           Multiple instances of **-L** options can be specified.
    


## OPERANDS



           An _operand_ is either in the form of a pathname or the form **-l**
           _library_.  At least one operand of the pathname form shall be
           specified. The following operands shall be supported:
    
           _file._**f** The pathname of a FORTRAN source file to be compiled and
                     optionally passed to the link editor. The filename
                     operand shall be of this form if the **-c** option is used.
    
           _file._**a** A library of object files typically produced by _ar_ , and
                     passed directly to the link editor. Implementations may
                     recognize implementation-defined suffixes other than **.a**
                     as denoting object file libraries.
    
           _file._**o** An object file produced by _fort77_ **-c** and passed directly
                     to the link editor. Implementations may recognize
                     implementation-defined suffixes other than **.o** as
                     denoting object files.
    
           The processing of other files is implementation-defined.
    
           **-l** _library_
                     (The letter ell.) Search the library named:
    
                         lib _library_.a
    
                     A library is searched when its name is encountered, so
                     the placement of a **-l** operand is significant. Several
                     standard libraries can be specified in this manner, as
                     described in the EXTENDED DESCRIPTION section.
                     Implementations may recognize implementation-defined
                     suffixes other than **.a** as denoting libraries.
    


## STDIN



           Not used.
    


## INPUT FILES



           The input file shall be one of the following: a text file
           containing FORTRAN source code; an object file in the format
           produced by _fort77_ **-c** ; or a library of object files, in the format
           produced by archiving zero or more object files, using _ar_.
           Implementations may supply additional utilities that produce files
           in these formats. Additional input files are implementation-
           defined.
    
           A <tab> encountered within the first six characters on a line of
           source code shall cause the compiler to interpret the following
           character as if it were the seventh character on the line (that
           is, in column 7).
    


## ENVIRONMENT VARIABLES



           The following environment variables shall affect the execution of
           _fort77_ :
    
           _LANG_      Provide a default value for the internationalization
                     variables that are unset or null. (See the Base
                     Definitions volume of POSIX.1‐2017, _Section 8.2_ ,
                     _Internationalization Variables_ for the precedence of
                     internationalization variables used to determine the
                     values of locale categories.)
    
           _LC_ALL_    If set to a non-empty string value, override the values
                     of all the other internationalization variables.
    
           _LC_CTYPE_  Determine the locale for the interpretation of sequences
                     of bytes of text data as characters (for example,
                     single-byte as opposed to multi-byte characters in
                     arguments and input files).
    
           _LC_MESSAGES_
                     Determine the locale that should be used to affect the
                     format and contents of diagnostic messages written to
                     standard error.
    
           _NLSPATH_   Determine the location of message catalogs for the
                     processing of _LC_MESSAGES_.
    
           _TMPDIR_    Determine the pathname that should override the default
                     directory for temporary files, if any.
    


## ASYNCHRONOUS EVENTS



           Default.
    


## STDOUT



           Not used.
    


## STDERR



           The standard error shall be used only for diagnostic messages.  If
           more than one _file_ operand ending in **.f**(or possibly other
           unspecified suffixes) is given, for each such file:
    
               "%s:\n", <_file_ >
    
           may be written to allow identification of the diagnostic message
           with the appropriate input file.
    
           This utility may produce warning messages about certain conditions
           that do not warrant returning an error (non-zero) exit value.
    


## OUTPUT FILES



           Object files, listing files, and executable files shall be
           produced in unspecified formats.
    


## EXTENDED DESCRIPTION



       **Standard Libraries**
           The _fort77_ utility shall recognize the following **-l** operand for
           the standard library:
    
           **-l f** This library contains all functions referenced in the
                     ANSI X3.9‐1978 standard. This operand shall not be
                     required to be present to cause a search of this
                     library.
    
           In the absence of options that inhibit invocation of the link
           editor, such as **-c** , the _fort77_ utility shall cause the equivalent
           of a **-l f** operand to be passed to the link editor as the last **-l**
           operand, causing it to be searched after all other object files
           and libraries are loaded.
    
           It is unspecified whether the library **libf.a** exists as a regular
           file. The implementation may accept as **-l** operands names of
           objects that do not exist as regular files.
    
       **External Symbols**
           The FORTRAN compiler and link editor shall support the
           significance of external symbols up to a length of at least 31
           bytes; case folding is permitted. The action taken upon
           encountering symbols exceeding the implementation-defined maximum
           symbol length is unspecified.
    
           The compiler and link editor shall support a minimum of 511
           external symbols per source or object file, and a minimum of 4095
           external symbols total. A diagnostic message is written to
           standard output if the implementation-defined limit is exceeded;
           other actions are unspecified.
    


## EXIT STATUS



           The following exit values shall be returned:
    
            0    Successful compilation or link edit.
    
           >0    An error occurred.
    


## CONSEQUENCES OF ERRORS



           When _fort77_ encounters a compilation error, it shall write a
           diagnostic to standard error and continue to compile other source
           code operands. It shall return a non-zero exit status, but it is
           implementation-defined whether an object module is created. If the
           link edit is unsuccessful, a diagnostic message shall be written
           to standard error, and _fort77_ shall exit with a non-zero status.
    
           _The following sections are informative._
    


## APPLICATION USAGE



           None.
    


## EXAMPLES



           The following usage example compiles **xyz.f** and creates the
           executable file **foo** :
    
               fort77 -o foo xyz.f
    
           The following example compiles **xyz.f** and creates the object file
           **xyz.o** :
    
               fort77 -c xyz.f
    
           The following example compiles **xyz.f** and creates the executable
           file **a.out** :
    
               fort77 xyz.f
    
           The following example compiles **xyz.f** , links it with **b.o** , and
           creates the executable **a.out** :
    
               fort77 xyz.f b.o
    


## RATIONALE



           The name of this utility was chosen as _fort77_ to parallel the
           renaming of the C compiler. The name _f77_ was not chosen to avoid
           problems with historical implementations. The ANSI X3.9‐1978
           standard was selected as a normative reference because the ISO/IEC
           version of FORTRAN-77 has been superseded by the ISO/IEC 1539:1991
           standard.
    
           The file inclusion and symbol definition **#define** mechanisms used
           by the _c99_ utility were not included in this volume of
           POSIX.1‐2017—even though they are commonly implemented—since there
           is no requirement that the FORTRAN compiler use the C
           preprocessor.
    
           The **-onetrip** option was not included in this volume of
           POSIX.1‐2017, even though many historical compilers support it,
           because it is derived from FORTRAN-66; it is an anachronism that
           should not be perpetuated.
    
           Some implementations produce compilation listings. This aspect of
           FORTRAN has been left unspecified because there was controversy
           concerning the various methods proposed for implementing it: a **-V**
           option overlapped with historical vendor practice and a naming
           convention of creating files with **.l** suffixes collided with
           historical _lex_ file naming practice.
    
           There is no **-I** option in this version of this volume of
           POSIX.1‐2017 to specify a directory for file inclusion. An INCLUDE
           directive has been a part of the Fortran-90 discussions, but an
           interface supporting that standard is not in the current scope.
    
           It is noted that many FORTRAN compilers produce an object module
           even when compilation errors occur; during a subsequent
           compilation, the compiler may patch the object module rather than
           recompiling all the code. Consequently, it is left to the
           implementor whether or not an object file is created.
    
           A reference to MIL-STD-1753 was removed from an early proposal in
           response to a request from the POSIX FORTRAN-binding standard
           developers. It was not the intention of the standard developers to
           require certification of the FORTRAN compiler, and
           IEEE Std 1003.9‐1992 does not specify the military standard or any
           special preprocessing requirements. Furthermore, use of that
           document would have been inappropriate for an international
           standard.
    
           The specification of optimization has been subject to changes
           through early proposals. At one time, **-O** and **-N** were Booleans:
           optimize and do not optimize (with an unspecified default). Some
           historical practice led this to be changed to:
    
           **-O** 0      No optimization.
    
           **-O** 1      Some level of optimization.
    
           **-O** _n_      Other, unspecified levels of optimization.
    
           It is not always clear whether ``good code generation'' is the
           same thing as optimization. Simple optimizations of local actions
           do not usually affect the semantics of a program. The **-O** 0 option
           has been included to accommodate the very particular nature of
           scientific calculations in a highly optimized environment;
           compilers make errors. Some degree of optimization is expected,
           even if it is not documented here, and the ability to shut it off
           completely could be important when porting an application. An
           implementation may treat **-O** 0 as ``do less than normal'' if it
           wishes, but this is only meaningful if any of the operations it
           performs can affect the semantics of a program. It is highly
           dependent on the implementation whether doing less than normal is
           logical. It is not the intent of the **-O** 0 option to ask for
           inefficient code generation, but rather to assure that any
           semantically visible optimization is suppressed.
    
           The specification of standard library access is consistent with
           the C compiler specification. Implementations are not required to
           have **/usr/lib/libf.a** , as many historical implementations do, but
           if not they are required to recognize **f** as a token.
    
           External symbol size limits are in normative text; conforming
           applications need to know these limits. However, the minimum
           maximum symbol length should be taken as a constraint on a
           conforming application, not on an implementation, and consequently
           the action taken for a symbol exceeding the limit is unspecified.
           The minimum size for the external symbol table was added for
           similar reasons.
    
           The CONSEQUENCES OF ERRORS section clearly specifies the behavior
           of the compiler when compilation or link-edit errors occur. The
           behavior of several historical implementations was examined, and
           the choice was made to be silent on the status of the executable,
           or **a.out** , file in the face of compiler or linker errors. If a
           linker writes the executable file, then links it on disk with
           _lseek_()s and _write_()s, the partially linked executable file can be
           left on disk and its execute bits turned off if the link edit
           fails. However, if the linker links the image in memory before
           writing the file to disk, it need not touch the executable file
           (if it already exists) because the link edit fails. Since both
           approaches are historical practice, a conforming application shall
           rely on the exit status of _fort77_ , rather than on the existence or
           mode of the executable file.
    
           The **-g** and **-s** options are not specified as mutually-exclusive.
           Historically, these two options have been mutually-exclusive, but
           because both are so loosely specified, it seemed appropriate to
           leave their interaction unspecified.
    
           The requirement that conforming applications specify compiler
           options separately is to reserve the multi-character option name
           space for vendor-specific compiler options, which are known to
           exist in many historical implementations. Implementations are not
           required to recognize, for example, **-gc** as if it were **-g -c** ; nor
           are they forbidden from doing so. The SYNOPSIS shows all of the
           options separately to highlight this requirement on applications.
    
           Echoing filenames to standard error is considered a diagnostic
           message because it would otherwise be difficult to associate an
           error message with the erring file. They are described with
           ``may'' to allow implementations to use other methods of
           identifying files and to parallel the description in _c99_.
    


## FUTURE DIRECTIONS



           Future versions of this standard may withdraw this utility. There
           are implementations of compilers that conform to much more recent
           versions of the FORTRAN programming language. Since there is no
           active FORTRAN binding to POSIX.1‐2008, this standard does not
           need to specify any compiler.
    


* * *