Abstract:
The present disclosure simplifies programming debugging by dynamically injecting debugger compiled instrumentation into the debuggee process such that the debuggee process executes the instrumentation without executing the debugger. In one example method, the debugger controls compiling a description of the instrumentation as an instrumentation method. The debugger can then write the instrumentation method into the debuggee. The debuggee can save the state of a target method of the debuggee process at a predetermined location. The debuggee process calls the instrumentation method from the debuggee. In addition, the state of the target method can be restored and the resumed from the predetermined location after the instrumentation method executes.

Description:
BACKGROUND 
       [0001]    Program debugging, or debugging, is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware to make the computer program behave as expected. Debugging in general is a lengthy, tiresome task, and programmers often use a software tool such as a debugger operating on a debuggee process to monitor execution of the computer program and to perform program debugging. During investigation of the program, the programmer may stop the execution of the debuggee process, collect data values, or otherwise affect the execution of the debuggee process based on the values of the variables. The program may know the points of investigation and build the logic into the program, or the programmer can make use of the debugger to place instrumentation. 
         [0002]    The use of the debugger can provide difficulties in program debugging. For example, the range of possible instrumentation varies depending on the debugger used, and thus the programmer will use care to select the correct debugger if one even exists. Further, the cost—in terms of delayed execution while the instrumentation is evaluated—is often prohibitive because the delayed execution with the debugger is often several orders of magnitude slower than if the programmer had built the same instrumentation into the program. In many cases, the programmer will often choose to exit the debugger and modify the computer program rather than make use of the instrumentation features of the debugger. 
         [0003]    Previous attempts to address these difficulties have included using breakpoints and debugger/debuggee communications with operating system facilities to provide instrumentation. The debugger is involved at every execution of the instrumentation. Program debuggers often allow the programmer to specify instrumentation points (such as conditional breakpoints, tracepoints, or the like) and a description to address ad hoc needs in the debugging process. The debugger implements these points based on the instrumentation point capability of the debugger. The debugger places an instrumentation point, such as a software interrupt instruction, into the program code of the debuggee process. When the debuggee executes the interrupt, the operating system pauses the execution of the debuggee process and notifies the debugger. The debugger executes the behavior specified in the instrumentation point description. For example, in the case of a conditional breakpoint, the debugger evaluates the conditional expression. Because these expressions often refer to program variables, the debugger makes call to the operating system to read the memory contents of the debuggee process and extract the variable values. If the condition evaluates true then the debugger notifies the programmer. Otherwise, the debugger notifies the operating system that then continues the execution of the debuggee process. 
         [0004]    This course of pausing the debuggee process, executing the debugger, querying the debugger state, and continuing the execution of the debuggee process requires the execution of a relatively large amount of code. Further, specifying this instrumentation at a program location that executes frequently can cause a relatively large perturbation in the execution of the debuggee process even if the condition is never true. This often makes a conditional breakpoint feature impractical to use. 
       SUMMARY 
       [0005]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is this summary intended to be used to limit the scope of the claimed subject matter. 
         [0006]    The present disclosure simplifies programming debugging by dynamically injecting debugger compiled instrumentation into the debuggee process such that the debuggee process executes the instrumentation without executing the debugger. In one example method, the debugger controls compiling a description of the instrumentation as an instrumentation method. The debugger can then write the instrumentation method into the debuggee. The debuggee can save the state of a target method of the debuggee process at a predetermined location. The debuggee process calls the instrumentation method from the debuggee. In addition, the state of the target method can be restored and the resumed from the predetermined location after the instrumentation method executes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. 
           [0008]      FIG. 1  is a schematic diagram illustrating a computer system according to one embodiment of the present disclosure. 
           [0009]      FIG. 2  is a block diagram illustrating one embodiment of a debugger system computer including a debugger system application interfacing with a debuggee process computer. 
           [0010]      FIG. 3  is a block diagram illustrating one embodiment of a method of the debugger system application and the debuggee process computer. 
           [0011]      FIG. 4  is a flow diagram illustrating one embodiment of a feature of the method performed in  FIG. 3 . 
           [0012]      FIG. 5  is a flow diagram illustrating one embodiment of another feature of the method performed in  FIG. 3   
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. It is to be understood that features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise. 
         [0014]    As illustrated in  FIG. 1 , an exemplary computer system that can be employed to implement one or more parts of an example debugger system and/or an example debugging agent and/or an example debuggee process includes a computing device, such as computing device  100 . In a basic configuration, computing device  100  typically includes processing unit(s) (i.e., processor(s))  102  and memory  104 . Depending on the exact configuration and type of computing device, memory  104  may be volatile (such as random access memory (RAM)), non-volatile (such as read only memory (ROM), flash memory, etc.), or some combination of the two. This basic configuration is illustrated in  FIG. 1  by dashed line  106 . 
         [0015]    Computing device  100  may also have additional features/functionality. For example, computing device  100  may also include additional storage (removable and/or non-removable) including, but not limited to, magnetic or optical disks, or tape, or flash storage devices. Such additional storage is illustrated in  FIG. 1  by removable storage  108  and non-removable storage  110 . Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any suitable method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Memory  104 , removable storage  108  and non-removable storage  110  are all examples of computer storage media. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, universal serial bus (USB) flash drive, flash memory card, or other flash storage devices, or any other medium that can be used to store the desired information and that can be accessed by computing device  100 . Any such computer storage media may be part of computing device  100 . 
         [0016]    Computing device  100  includes one or more communication connections  114  that allow computing device  100  to communicate with other computers/applications  115 . Computing device  100  may also include input device(s)  112 , such as keyboard, pointing device (e.g., mouse), pen, voice input device, touch input device, etc. Computing device  100  may also include output device(s)  111 , such as a display, speakers, printer, etc. 
         [0017]    In one implementation, computing device  100  includes a debugger system application  200 . Debugger system application  200  is described in further detail below with reference to  FIG. 2 . One embodiment of a debugger system computer  100  (e.g., computing device  100  illustrated in  FIG. 1 ) comprising a debugger system application  200  interfacing with a debuggee process computer  206  (e.g., a computing device similar to computing device  100  illustrated in  FIG. 1 ) comprising a debugging agent  208  and a debuggee process  210  is illustrated in  FIG. 2 . 
         [0018]    Debugger system application  200 , debugging agent  208 , and debuggee process  210  can be implemented on any suitable type and suitable number of computer systems, such as computing device  100  illustrated in  FIG. 1 . In one embodiment, debugger system application  200  is one of the application programs that reside on computing device  100 , debugging agent  208  is one of the application programs that reside on debuggee process computer  206 , and debuggee process  210  is one of the application programs that reside on debuggee process computer  206 . Debugger system application  200 , however, can alternatively or additionally be embodied as computer executable instructions on one or more computers and/or in different variations than illustrated in  FIG. 1 . Alternatively or additionally, one or more parts of debugger system application  200  can be stored in system memory  104 , on other computers/applications  115 , or other such suitable variations for running a debugger system application. 
         [0019]    In one embodiment, debugging agent  208  is on a debuggee process computer  206  which is remote from debugger system computer  100  which includes debugger system application  200 . In other embodiments, however, debugging agent  208  and/or debuggee process  210  resides on the same computer as debugger system application  200 . The debugger system application is configured to request a current call stack of multiple threads of debuggee process  210 . In the embodiment illustrated in  FIG. 2 , debuggee process  210  includes threads  1 ,  2 , . . . N which correspondingly have thread registers and stack memory indicated at  212   a ,  212   b , . . .  212   c.    
         [0020]    Embodiments of debugger system application  200 , debugging agent  208 , and debuggee process  210  are described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Embodiments may be practiced in distributing computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computer environment, program modules may be located in both local and remote computer storage media including media storage devices. 
         [0021]      FIG. 3  illustrates an example process  300  operating on the system illustrated in  FIG. 2 . The process  300  includes features  302  prior to adding instrumentation and features  304  after adding instrumentation. 
         [0022]    Features  302  of process  300  illustrate a target method T that is at least a portion of code to be debugged. In one example, target method T represents a portion of code of the application related to a segment that will include an instrumentation breakpoint. In other examples, the code can include more than just the related segment. Location L represents the location of the instrumentation breakpoint included into the target method T, which is often designated by the developer. The target method T includes a first portion  306  TpreL that includes the bytes of code to be executed before location L, and target method T includes a second portion  308  TpostL that includes the bytes of code to be executed after location L. 
         [0023]    In this example, the debugger  200  will inject code implementing the instrumentation directly into the debuggee process  210 . The debuggee process  210  can then execute the instrumentation without the debugger  200 . Many kinds of instrumentation can be added including conditional breakpoints, conditional traces, data structure integrity verification, pre-conditional and post-conditional verifications, event generation, statement timing, and so on. In the example process  300  illustrated in  FIG. 3 , the instrumentation is implemented as an instrumentation method M that is called from the location L. 
         [0024]    Features  304  of process  300  illustrate the instrumentation implemented as the instrumentation method M. In one example, the code for instrumentation method M is compiled either by the debugger  200  or elsewhere but still under the control of the debugger  200 . The debugger  200  allocates memory in the debuggee process  210  to include instrumentation method M, and then writes the bytes of the instrumentation method M to the debuggee process  210 . 
         [0025]    The debugger  200  also allocates memory in the debuggee process computer  206  to include a modified version of the target method T, which is called new T  310 . New T  310  is generated prior to the execution of target method T. As the process executes the application, the process encounters an instruction  312  to create New T  310 . New T  310  includes a copy of T in the debuggee process  210  that includes the first portion  306  TpreL and the second portion  308  TpostL. 
         [0026]    New T  310  includes a feature  314  to call instrumentation method M inserted at location L. Feature  314  includes the ability to save the state of target method T at  316 , run the instrumentation method M at  318 , restore the state of the target method T at  320 , and then proceed with TpostL  308 . In one example, feature  314  can include a trampoline at location L that saves the register state of T  316  at the point after TpreL  306 . The feature  314  marshalls application parameters and calls  318  the instrumentation method M. After implementation method M completes, in one example, the feature  314  restores the register state  320 . The debugger  200  can then write the bytes of TpostL  308  to the new T  310 . 
         [0027]    The original code for the target method T can be modified to redirect to the call to the new T  310 . When the instrumentation is removed the original target method T is restored and the memory in the debuggee process computer  206  used for the new T  310  can be reclaimed. In certain examples, a developer can place additional instrumentation points in the target method T. If an additional instrumentation points are included in the target method T, one example applies the process  300  the new T  310 . In some examples, the instrumentation can be removed in an order other than that described above, the trampoline for the removed instrumentation can be disabled with a “no operation” instruction until the removal is complete. 
         [0028]    An example debugger  200  can include several features to facilitate the process  300 . For example, the debugger can include the capability to compile, or request the compilation of, the instrumentation it supports. The debugger  200  can also maintain symbolic methods that it has relocated in order to present fewer perturbations during debugging. The debugger can also create the instrumentation in the source language of the debuggee process  210 , that is the language of the target method T, or it can use any other suitable language to describe the instrumentation. Further, one or more threads are capable of executing on a multiprocessor debuggee system computer  206 . In this case, the debugger  200  moves the point of execution to the analogous point in the new T  310 . 
         [0029]      FIG. 4  illustrates an example process  400  for inserting instrumentation into the target method T. In the method  400 , the developer or other user of the debugger enters a description of the instrumentation at  402 . For example, the description of the instrumentation can include “Stop in target method T at line  10  if x&gt;100.” The debugger  200  compiles the description, or requests compilation from a language compiler, into code bytes for a method at  404 . For example, the compiled description can include: “void M(int x) {if (x&gt;100) DebugBreak( );}” The debugger  200  allocates space in the debuggee system computer  206  for new T  310  and instrumentation method M at  406 . The debugger  200  writes the new T  310  and the instrumentation method M to the debuggee system computer  206  at  408 . The debugger  200  writes a jump from the target method T to the new T  310  remembering the original state at  410  of the target method T at location L. The debugger  200  also finds the stack frames executing in the target method T and adjust the point of execution to new T  310  at  412 . The debugger  200  also remaps symbolic information for the target method T to the new T  310  at  414 . 
         [0030]      FIG. 5  illustrates an example process  500  for removing instrumentation, such as instrumentation added in process  400  or another process. The debugger  200  permits any debuggee thread executing the instrumentation method M to continue executing until it returns from the target method M at  502 . The debugger  200  restores the original state of target method T from  410  above at  504 . The debugger releases the memory of the debuggee system computer  206  that was allocated for the new T  310  and the instrumentation method M at  506 . The debugger  200  finds the stack frames that are executing in the new T  310  and adjusts the point of execution to the target method T at  508 . The debugger also restores the original mapping of the symbolic information of the target method T at  510 . 
         [0031]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof. 
         [0032]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.