Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple Memory Heaps
Format
#include <string.h>
void *_debug_memset(void *dest, int c, size_t count,
const char *file, size_t line);
Language Level: Extension
_debug_memset is the debug version of memset. Like memset, it sets the first count bytes of dest to the value c. The value of c is converted to an unsigned character.
_debug_memset validates the heap after setting the bytes, and performs this check only when the target is within a heap. _debug_memset makes an implicit call to _heap_check. If _debug_memset detects a corrupted heap when it makes a call to _heap_check, _debug_memset will report the file name file and line number line in a message.
Note: _debug_memset checks only the current default heap. Therefore, this debug support will not check all heaps within applications that have multiple user heaps.
To use _debug_memset, you must compile with the debug memory -qheapdebug compiler option. This option maps all memset calls to _debug_memset. You do not have to change your source code, in order for _debug_memset to verify the heap.
Note: The -qheapdebug option maps all calls to other string functions and all calls to memory management functions (including a heap-specific version), to their debug counterparts. To prevent a call from being mapped, parenthesize the function name.
Return Value
_debug_memset returns a pointer to dest.
Example
This example contains a programming error. The invocation of memset
that puts 'B' in the buffer specifies the wrong count, and stores
bytes past the end of the buffer.
#include <stdlib.h> #include <string.h> #include <stdio.h>
#define BUF_SIZE 20
int main(void)
{
char *buffer, *buffer2;
char *string;
buffer = (char*)calloc(1, BUF_SIZE+1); /* +1 for null-terminator */
string = (char*)memset(buffer, 'A', 10);
printf("\nBuffer contents: %s\n", string);
memset(buffer+10, 'B', 20);
return 0;
/****************************************************************************
The output should be:
Buffer contents: AAAAAAAAAA
End of allocated object 0x00073c80 was overwritten at 0x00073c95.
The first eight bytes of the memory block (in hex) are: 4141414141414141.
This memory block was (re)allocated at line number 12 in memset.c.
Heap state was valid at line 14 of memset.c.
Memory error detected at line 16 of memset.c.
****************************************************************************/
}
Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple
Memory Heaps
Debugging Problems with Heap
Memory
-qheapdebug Compiler
Option
_debug_calloc - Allocate and Initialize
Memory
_debug_free - Free Allocated Memory
_debug_heapmin - Free Unused Memory in the
Default Heap
_debug_malloc - Allocate Memory
_debug_memcpy - Copy Bytes
_debug_memmove - Copy Bytes
_debug_realloc - Reallocate Memory Block
_debug_strcat - Concatenate Strings
_debug_strcpy - Copy Strings
_debug_strncat - Concatenate Strings
_debug_strncpy - Copy Strings
_debug_strnset - Set Characters in String
_debug_strset - Set Characters in String
_debug_ucalloc - Reserve and Initialize
Memory from User Heap
_debug_uheapmin - Free Unused Memory in
User Heap
_debug_umalloc - Reserve Memory Block from
User Heap
