/**//*****************************************************************
* ?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 );
}
大概解釋一下，這里的函數都是什么作用：
1、首先是剛開始的六個函數，這六個函數的作用就是讓接下來的內存調試函數輸出調試信息到控制臺。后面的函數都是實際調試內存的，如果之前調用了這六個函數，那么調試信息會輸出到控制臺。
2、_CrtMemDumpAllObjectsSince( NULL )函數的作用是輸出目前為止，在堆中申請的空間的所有信息，包括地址，大小，內容。
3、_CrtDumpMemoryLeaks( )函數的作用是檢測到目前為止，還有哪些堆中申請的內存沒有釋放，包括地址，大小等
4、SET_CRT_DEBUG_FIELD( _CRTDBG_LEAK_CHECK_DF )宏的作用是在程序結束的時候檢測堆內存是否還有泄露，作用同CrtDumpMemoryLeaks( )一樣，只不過是在所有該釋放的都結束之后，進行最后的檢查。
（未完，以后補充）