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Debug Routines

 

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The latest version of this topic can be found at Debug Routines.

The debug version of the C run-time library supplies many diagnostic services that make debugging programs easier and allow developers to:

  • Step directly into run-time functions during debugging

  • Resolve assertions, errors, and exceptions

  • Trace heap allocations and prevent memory leaks

  • Report debug messages to the user

To use these routines, the _DEBUG flag must be defined. All of these routines do nothing in a retail build of an application. For more information on how to use the new debug routines, see CRT Debugging Techniques.

Debug Versions of the C Run-Time Library Routines

Routine Use .NET Framework equivalent
_ASSERT Evaluate an expression and generates a debug report when the result is FALSE System::Diagnostics::Debug::Assert
_ASSERTE Similar to _ASSERT, but includes the failed expression in the generated report System::Diagnostics::Debug::Assert
_CrtCheckMemory Confirm the integrity of the memory blocks allocated on the debug heap System::Diagnostics::PerformanceCounter
_CrtDbgBreak Sets a break point. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtDbgReport, _CrtDbgReportW Generate a debug report with a user message and send the report to three possible destinations System::Diagnostics::Debug::Write, System::Diagnostics::Debug::Writeline, System::Diagnostics::Debug::WriteIf, System::Diagnostics::Debug::WriteLineIf
_CrtDoForAllClientObjects Call an application-supplied function for all _CLIENT_BLOCK types on the heap Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtDumpMemoryLeaks Dump all of the memory blocks on the debug heap when a significant memory leak has occurred Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtIsMemoryBlock Verify that a specified memory block is located within the local heap and that it has a valid debug heap block type identifier Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtIsValidHeapPointer Verifies that a specified pointer is in the local heap Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtIsValidPointer Verify that a specified memory range is valid for reading and writing Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtMemCheckpoint Obtain the current state of the debug heap and store it in an application-supplied _CrtMemState structure Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtMemDifference Compare two memory states for significant differences and return the results Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtMemDumpAllObjectsSince Dump information about objects on the heap since a specified checkpoint was taken or from the start of program execution Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtMemDumpStatistics Dump the debug header information for a specified memory state in a user-readable form System::Diagnostics::PerformanceCounter
_CrtReportBlockType Returns the block type/subtype associated with a given debug heap block pointer. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetAllocHook Install a client-defined allocation function by hooking it into the C run-time debug memory allocation process Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetBreakAlloc Set a breakpoint on a specified object allocation order number Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetDbgFlag Retrieve or modify the state of the _crtDbgFlag flag to control the allocation behavior of the debug heap manager Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetDumpClient Install an application-defined function that is called every time a debug dump function is called to dump _CLIENT_BLOCK type memory blocks Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetReportFile Identify the file or stream to be used as a destination for a specific report type by _CrtDbgReport Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetReportHook Install a client-defined reporting function by hooking it into the C run-time debug reporting process Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetReportHook2, _CrtSetReportHookW2 Installs or uninstalls a client-defined reporting function by hooking it into the C run-time debug reporting process. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_CrtSetReportMode Specify the general destination(s) for a specific report type generated by _CrtDbgReport Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_RPT[0,1,2,3,4] Track the application's progress by generating a debug report by calling _CrtDbgReport with a format string and a variable number of arguments. Provides no source file and line number information. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_RPTF[0,1,2,3,4] Similar to the _RPTn macros, but provides the source file name and line number where the report request originated Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_calloc_dbg Allocate a specified number of memory blocks on the heap with additional space for a debugging header and overwrite buffers Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_expand_dbg Resize a specified block of memory on the heap by expanding or contracting the block Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_free_dbg Free a block of memory on the heap Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_fullpath_dbg, _wfullpath_dbg Create an absolute or full path name for the specified relative path name, using _malloc_dbg to allocate memory. System::IO::File::Create
_getcwd_dbg, _wgetcwd_dbg Get the current working directory, using _malloc_dbg to allocate memory. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_malloc_dbg Allocate a block of memory on the heap with additional space for a debugging header and overwrite buffers Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_msize_dbg Calculate the size of a block of memory on the heap Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_realloc_dbg Reallocate a specified block of memory on the heap by moving and/or resizing the block Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.
_strdup_dbg, _wcsdup_dbg Duplicates a string, using _malloc_dbg to allocate memory. System::String::Clone
_tempnam_dbg, _wtempnam_dbg Generate names you can use to create temporary files, using _malloc_dbg to allocate memory. Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

The debug routines can be used to step through the source code for most of the other C run-time routines during the debugging process. However, Microsoft considers some technology to be proprietary and, therefore, does not provide the source code for these routines. Most of these routines belong to either the exception handling or floating-point processing groups, but a few others are included as well. The following table lists these routines.

C Run-Time Routines That Are Not Available in Source Code Form

acos, acosf, acosl _fpclass _nextafter
asin _fpieee_flt pow
atan, atan2 _fpreset printf, _printf_l, wprintf, _wprintf_l, printf_s, _printf_s_l, wprintf_s, _wprintf_s_l*
_cabs frexp _scalb
ceil _hypot scanf, _scanf_l, wscanf, _wscanf_l, scanf_s, _scanf_s_l, wscanf_s, _wscanf_s_l*
_chgsign, _chgsignf, _chgsignl _isnan setjmp
_clear87, _clearfp _j0 sin
_control87, _controlfp, __control87_2 _j1 sinh
copysign, copysignf, copysignl, _copysign, _copysignf, _copysignl _jn sqrt
cos ldexp _status87, _statusfp
cosh log tan
Exp log10 tanh
fabs _logb _y0
_finite longjmp _y1
floor _matherr _yn
fmod modf

* Although source code is available for most of this routine, it makes an internal call to another routine for which source code is not provided.

Some C run-time functions and C++ operators behave differently when called from a debug build of an application. (Note that a debug build of an application can be done by either defining the _DEBUG flag or by linking with a debug version of the C run-time library.) The behavioral differences usually consist of extra features or information provided by the routine to support the debugging process. The following table lists these routines.

Routines that Behave Differently in a Debug Build of an Application

C abort routine C++ delete operator
C assert routine C++ new operator

See Also

Run-Time Routines by Category
Run-Time Error Checking