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#include <stddef.h>
#include <stdlib.h>
#include <limits.h>
#include "libc.h"
/* Ensure that at least 32 atexit handlers can be registered without malloc */
#define COUNT 32
static struct fl
{
struct fl *next;
void (*f[COUNT])(void);
} builtin, *head;
static int run_atexit_functions(void)
{
int i;
for (; head; head=head->next) {
for (i=COUNT-1; i>=0 && !head->f[i]; i--);
for (; i>=0; i--) head->f[i]();
}
return 0;
}
int (*const __funcs_on_exit)(void) = run_atexit_functions;
int atexit(void (*func)(void))
{
static int lock;
int i;
/* Hook for atexit extensions */
if (libc.atexit) return libc.atexit(func);
LOCK(&lock);
/* Defer initialization of head so it can be in BSS */
if (!head) head = &builtin;
/* If the current function list is full, add a new one */
if (head->f[COUNT-1]) {
struct fl *new_fl = calloc(sizeof(struct fl), 1);
if (!new_fl) {
UNLOCK(&lock);
return -1;
}
new_fl->next = head;
head = new_fl;
}
/* Append function to the list. */
for (i=0; i<COUNT && head->f[i]; i++);
head->f[i] = func;
UNLOCK(&lock);
return 0;
}
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