_debug_memset — Set bytes to value

Format

#include <string.h>
void *_debug_memset(void *dest, int c, size_t count, const char *file, size_t line);

Purpose

This 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 reports the file name file and line number line in a message.

Return values

Returns a pointer to dest.

Examples

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.

/*  _debug_memset.c  */ 
#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 is similar to:

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 _debug_memset.c.
Heap state was valid at line 14 of _debug_memset.c.
Memory error detected at line 16 of _debug_memset.c.