Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple Memory Heaps
Format
#include <string.h>
char *_debug_strset(char *string, size_t c,
const char *file, size_t line);
Language Level: Extension
_debug_strset is the debug version of strset. Like strset, it sets all characters of string, except the ending null character (\0), to c (converted to a char).
_debug_strset validates the heap after setting all characters of string, and performs this check only when the target is within a heap. _debug_strset makes an implicit call to _heap_check. If _debug_strset detects a corrupted heap when it makes a call to _heap_check, _debug_strset will report the file name file and line number line in a message.
Note: _debug_strset 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_strset, you must compile with the debug memory -qheapdebug compiler option. This option maps all strset calls to _debug_strset. You do not have to change your source code, in order for _debug_strset 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_strset returns a pointer to the altered string.
There is no error return value.
Example
This example contains a programming error. The string, str,
was created without a null-terminator, and strset
propagates the letter 'k' until it finds what it thinks
is the null-terminator.
#include <stdlib.h> #include <stdio.h> #include <string.h>
int main(void)
{
char *str;
str = (char*)malloc(10);
strnset(str, 'x', 5);
strset(str+5, 'k');
printf("This is the string after strset: %s\n", str);
return 0;
/****************************************************************************
The output should be:
End of allocated object 0x00073c80 was overwritten at 0x00073c8a.
The first eight bytes of the memory block (in hex) are: 78787878786B6B6B.
This memory block was (re)allocated at line number 9 in strset.c.
Heap state was valid at line 11 of strset.c.
Memory error detected at line 12 of strnset.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_memset - Set Bytes to Value
_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_ucalloc - Reserve and Initialize
Memory from User Heap
_debug_uheapmin - Free Unused Memory in
User Heap
_debug_umalloc - Reserve Memory Block from
User Heap
