/**//*****************************************************************
* ?000 Microsoft Corporation *
* CRT_DBG1 *
* This simple program illustrates the basic debugging features *
* of the C runtime libraries, and the kind of debug output *
* that these features generate. *
*****************************************************************/
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <crtdbg.h>
// Disable deprecation warnings. The unsecure version of strcpy is
// used intentionally to show off debugging features.
#pragma warning (disable : 4996)
// This routine place comments at the head of a section of debug output
void OutputHeading( const char * explanation )
{
_RPT1( _CRT_WARN, "\n\n%s:\n**************************************\
************************************\n", explanation );
}
// The following macros set and clear, respectively, given bits
// of the C runtime library debug flag, as specified by a bitmask.
#ifdef _DEBUG
#define SET_CRT_DEBUG_FIELD(a) \
_CrtSetDbgFlag((a) | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))
#define CLEAR_CRT_DEBUG_FIELD(a) \
_CrtSetDbgFlag(~(a) & _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))
#else
#define SET_CRT_DEBUG_FIELD(a) ((void) 0)
#define CLEAR_CRT_DEBUG_FIELD(a) ((void) 0)
#endif
int main( )
{
char *p1, *p2;
_CrtMemState s1, s2, s3;
#ifndef _DEBUG
printf("Skipping this for non-debug mode.\n");
return 2;
#endif
// Send all reports to STDOUT
_CrtSetReportMode( _CRT_WARN, _CRTDBG_MODE_FILE );
_CrtSetReportFile( _CRT_WARN, _CRTDBG_FILE_STDOUT );
_CrtSetReportMode( _CRT_ERROR, _CRTDBG_MODE_FILE );
_CrtSetReportFile( _CRT_ERROR, _CRTDBG_FILE_STDOUT );
_CrtSetReportMode( _CRT_ASSERT, _CRTDBG_MODE_FILE );
_CrtSetReportFile( _CRT_ASSERT, _CRTDBG_FILE_STDOUT );
// Allocate 2 memory blocks and store a string in each
p1 = malloc( 34 );
strcpy( p1, "This is the p1 string (34 bytes)." );
p2 = malloc( 34 );
strcpy( p2, "This is the p2 string (34 bytes)." );
OutputHeading(
"Use _ASSERTE to check that the two strings are identical" );
_ASSERTE( strcmp( p1, p2 ) == 0 );
OutputHeading(
"Use a _RPT macro to report the string contents as a warning" );
_RPT2( _CRT_WARN, "p1 points to '%s' and \np2 points to '%s'\n", p1, p2 );
OutputHeading(
"Use _CRTMemDumpAllObjectsSince to check the p1 and p2 allocations" );
_CrtMemDumpAllObjectsSince( NULL );
free( p2 );
OutputHeading(
"Having freed p2, dump allocation information about p1 only" );
_CrtMemDumpAllObjectsSince( NULL );
// Store a memory checkpoint in the s1 memory-state structure
_CrtMemCheckpoint( &s1 );
// Allocate another block, pointed to by p2
p2 = malloc( 38 );
strcpy( p2, "This new p2 string occupies 38 bytes.");
// Store a 2nd memory checkpoint in s2
_CrtMemCheckpoint( &s2 );
OutputHeading(
"Dump the changes that occurred between two memory checkpoints" );
if ( _CrtMemDifference( &s3, &s1, &s2 ) )
_CrtMemDumpStatistics( &s3 );
// Free p2 again and store a new memory checkpoint in s2
free( p2 );
_CrtMemCheckpoint( &s2 );
OutputHeading(
"Now the memory state at the two checkpoints is the same" );
if ( _CrtMemDifference( &s3, &s1, &s2 ) )
_CrtMemDumpStatistics( &s3 );
strcpy( p1, "This new p1 string is over 34 bytes" );
OutputHeading( "Free p1 after overwriting the end of the allocation" );
free( p1 );
// Set the debug-heap flag so that freed blocks are kept on the
// linked list, to catch any inadvertent use of freed memory
SET_CRT_DEBUG_FIELD( _CRTDBG_DELAY_FREE_MEM_DF );
p1 = malloc( 10 );
free( p1 );
strcpy( p1, "Oops" );
OutputHeading( "Perform a memory check after corrupting freed memory" );
_CrtCheckMemory( );
// Use explicit calls to _malloc_dbg to save file name and line number
// information, and also to allocate Client type blocks for tracking
p1 = _malloc_dbg( 40, _NORMAL_BLOCK, __FILE__, __LINE__ );
p2 = _malloc_dbg( 40, _CLIENT_BLOCK, __FILE__, __LINE__ );
strcpy( p1, "p1 points to a Normal allocation block" );
strcpy( p2, "p2 points to a Client allocation block" );
// You must use _free_dbg to free a Client block
OutputHeading(
"Using free( ) to free a Client block causes an assertion failure" );
free( p1 );
free( p2 );
p1 = malloc( 10 );
OutputHeading( "Examine outstanding allocations (dump memory leaks)" );
_CrtDumpMemoryLeaks( );
// Set the debug-heap flag so that memory leaks are reported when
// the process terminates. Then, exit.
OutputHeading( "Program exits without freeing a memory block" );
SET_CRT_DEBUG_FIELD( _CRTDBG_LEAK_CHECK_DF );
}
大概解释一下，这里的函数都是什么作用：
1、首先是刚开始的六个函数，这六个函数的作用就是让接下来的内存调试函数输出调试信息到控制台。后面的函数都是实际调试内存的，如果之前调用了这六个函数，那么调试信息会输出到控制台。
2、_CrtMemDumpAllObjectsSince( NULL )函数的作用是输出目前为止，在堆中申请的空间的所有信息，包括地址，大小，内容。
3、_CrtDumpMemoryLeaks( )函数的作用是检测到目前为止，还有哪些堆中申请的内存没有释放，包括地址，大小等
4、SET_CRT_DEBUG_FIELD( _CRTDBG_LEAK_CHECK_DF )宏的作用是在程序结束的时候检测堆内存是否还有泄露，作用同CrtDumpMemoryLeaks( )一样，只不过是在所有该释放的都结束之后，进行最后的检查。
（未完，以后补充）