src/exit/atexit.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include "libc.h"
   4
   5 /* Ensure that at least 32 atexit handlers can be registered without malloc */
   6 #define COUNT 32
   7
   8 static struct fl
   9 {
  10         struct fl *next;
  11         void (*f[COUNT])(void *);
  12         void *a[COUNT];
  13 } builtin, *head;
  14
  15 static int slot;
  16 static volatile int lock[2];
  17
  18 void __funcs_on_exit()
  19 {
  20         void (*func)(void *), *arg;
  21         LOCK(lock);
  22         for (; head; head=head->next, slot=COUNT) while(slot-->0) {
  23                 func = head->f[slot];
  24                 arg = head->a[slot];
  25                 UNLOCK(lock);
  26                 func(arg);
  27                 LOCK(lock);
  28         }
  29 }
  30
  31 void __cxa_finalize(void *dso)
  32 {
  33 }
  34
  35 int __cxa_atexit(void (*func)(void *), void *arg, void *dso)
  36 {
  37         LOCK(lock);
  38
  39         /* Defer initialization of head so it can be in BSS */
  40         if (!head) head = &builtin;
  41
  42         /* If the current function list is full, add a new one */
  43         if (slot==COUNT) {
  44                 struct fl *new_fl = calloc(sizeof(struct fl), 1);
  45                 if (!new_fl) {
  46                         UNLOCK(lock);
  47                         return -1;
  48                 }
  49                 new_fl->next = head;
  50                 head = new_fl;
  51                 slot = 0;
  52         }
  53
  54         /* Append function to the list. */
  55         head->f[slot] = func;
  56         head->a[slot] = arg;
  57         slot++;
  58
  59         UNLOCK(lock);
  60         return 0;
  61 }
  62
  63 static void call(void *p)
  64 {
  65         ((void (*)(void))(uintptr_t)p)();
  66 }
  67
  68 int atexit(void (*func)(void))
  69 {
  70         return __cxa_atexit(call, (void *)(uintptr_t)func, 0);
  71 }