동적메모리 할당받은 메모리를 free() 할때요,

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <assert.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/uio.h>
#include <elf.h>
 
static unsigned long sdata, edata;
 
static void (*orig_free_hook)(void *, const void *);
 
void free_hook(void *ptr, const void *caller)
{
	unsigned long addr = (unsigned long) ptr;
	caller = caller; /* to make gcc happy */
 
	if (sdata <= addr && addr <= edata) {
		puts("try to free static data.. ignored");
		return;
	}
 
	__free_hook = orig_free_hook;
 
	free(ptr);
 
	__free_hook = free_hook;
}
 
static void find_data_segment(void)
{
	int fd;
	Elf64_Phdr *header = NULL;
	unsigned long type, value, pnum;
	struct iovec iov[2] = {
		{ &type, sizeof(type) },
		{ &value, sizeof(value) }
	};
 
	fd = open("/proc/self/auxv", O_RDONLY); /* auxiliary vector */
	do {
		readv(fd, iov, 2);
		if (type == AT_PHDR) /* start address of ELF program header */
			header = (Elf64_Phdr *) value;
		else if (type == AT_PHNUM) /* number of header entries */
			pnum = value;
	} while (type);
 
	assert(header);
	while (pnum--) {
		/* data segment will be "loaded" into memory and "writable" */
		if ((header->p_type == PT_LOAD) && (header->p_flags & PF_W)) {
			sdata = (unsigned long) header->p_vaddr;
			edata = sdata + header->p_memsz;
		}
		header++;
	}
	assert(sdata);
 
	close(fd);
}
 
static void malloc_init(void)
{
	orig_free_hook = __free_hook;
	__free_hook = free_hook;
 
	find_data_segment();
}
void (*__malloc_initialize_hook)(void) = malloc_init;
 
char buf1[1];
int main(void)
{
	void *ptr = malloc(1);
	static int buf2[2];
 
	free(buf1); /* ignored */
	free(buf2); /* ignored */
	free(ptr);
 
	return 0;
}