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	_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, _chgsignl	_isnan	setjmp
_clear87, _clearfp	_j0	sin
_control87, _controlfp, __control87_2	_j1	sinh
_copysign, _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

For more information about using the debug versions of the C++ operators in the preceding table, see Using the Debug Heap from C++.

See Also

Concepts

Run-Time Routines by Category

Run-Time Error Checking