Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple Memory Heaps
Format
#include <string.h>
char *_debug_strcat(char *string1, const char *string2,
const char *file, size_t file);
Language Level: Extension
_debug_strcat is the debug version of strcat. Like strcat, it concatenates string2 to string1 and ends the resulting string with the null character.
_debug_strcat validates the heap after concatenating the strings, and performs this check only when the target is within a heap. _debug_strcat makes an implicit call to _heap_check. If _debug_strcat detects a corrupted heap when it makes a call to _heap_check, _debug_strcat will report the file name file and line number file in a message.
Note: _debug_strcat 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_strcat, you must compile with the debug memory -qheapdebug compiler option. This option maps all strcat calls to _debug_strcat. You do not have to change your source code, in order for _debug_strcat 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_strcat returns a pointer to the concatenated
string string1.
Example
This example contains a programming error. The buffer1
object is not large enough to store the result after the string "
program" is concatenated.
#include <stdlib.h> #include <stdio.h> #include <string.h>
#define SIZE 10
int main(void)
{
char *buffer1;
char *ptr;
buffer1 = (char*)malloc(SIZE); strcpy(buffer1, "computer");
ptr = strcat(buffer1, " program");
printf("buffer1 = %s\n", buffer1);
return 0;
/****************************************************************************
The output should be similar to:
End of allocated object 0x00073c80 was overwritten at 0x00073c8a.
The first eight bytes of the memory block (in hex) are: 636F6D7075746572.
This memory block was (re)allocated at line number 12 in strcat.c.
Heap state was valid at line 13 of strcat.c.
Memory error detected at line 15 of strcat.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_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
