malloc封装用于检测内存越界

mymalloc.c

#define  BEGIN_MAGIC  0x3a3a3a3a
#define  END_MAGIC  0x5a5a5a5a

void *mymalloc(unsigned int size)
{
	char *ptr = (char *)malloc(size+12);
	unsigned int *ptmp = NULL;
	
	if(NULL == ptr)
		return NULL;

	memset(ptr,0,size+12);
	ptmp = (unsigned int *)ptr;
	*ptmp = size;
	ptmp = (unsigned int *)(ptr + 4);
	*ptmp = BEGIN_MAGIC;
	ptmp = (unsigned int *)(ptr + size + 8);
	*ptmp = END_MAGIC;
	
	return (void*)(ptr+8);
}

void mymemcheck(void *ptr)
{
	unsigned int *ptmp = NULL;
	char *ptr2 = (char *)((unsigned int)ptr - 8);
	unsigned int size = 0;
	
	ptmp = (unsigned int *)(ptr2);
	size = *ptmp;

	ptmp = (unsigned int *)(ptr2+4);
	assert(BEGIN_MAGIC == *ptmp);
	
	ptmp = (unsigned int *)(ptr2 + size + 8);
	assert(END_MAGIC == *ptmp);
}

void myfree(void *ptr)
{
	char *ptr2 = (char *)((unsigned int)ptr - 8);

	mymemcheck(ptr);
	
	free(ptr2);
}


用户thread函数

void *ptr = mymalloc(BUFFER_SIZE);

while(1)
{
  mymemcheck(ptr);
  /*do something*/
  mymemcheck(ptr);
  /*do something more*/
}

myfree(ptr);