Debugging Memory Heaps
Memory Management Functions
Managing Memory with Multiple Memory Heaps
Format
#include <string.h>
char *_debug_strncat(char *string1, const char *string2, size_t count,
const char *file, size_t line);
Language Level: Extension
_debug_strncat is the debug version of strncat. Like strncat, it appends the first count characters of string2 to string1 and ends the resulting string with a null character (\0). If count is greater than the length of string2, the length of string2 is used in place of count.
_debug_strncat validates the heap after appending the characters, and performs this check only when the target is within a heap. _debug_strncat makes an implicit call to _heap_check. If _debug_strncat detects a corrupted heap when it makes a call to _heap_check, _debug_strncat will report the file name file and line number line in a message.
Note: _debug_strncat 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_strncat, you must compile with the debug memory -qheapdebug compiler option. This option maps all strncat calls to _debug_strncat. You do not have to change your source code, in order for _debug_strncat 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_strncat returns a pointer to the joined string string1.
Example
This example contains a programming error. The buffer1
object is not large enough to store the result after eight
characters from the string " programming" are
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");
/* Call strncat with buffer1 and " programming" */
ptr = strncat(buffer1, " programming", 8);
printf("strncat: 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 strncat.c.
Heap state was valid at line 13 of strncat.c.
Memory error detected at line 17 of strncat.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_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
