src/exit/atexit.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include "libc.h"
   4 #include "lock.h"
   5
   6 /* Ensure that at least 32 atexit handlers can be registered without malloc */
   7 #define COUNT 32
   8
   9 static struct fl
  10 {
  11         struct fl *next;
  12         void (*f[COUNT])(void *);
  13         void *a[COUNT];
  14 } builtin, *head;
  15
  16 static int slot;
  17 static volatile int lock[1];
  18
  19 void __funcs_on_exit()
  20 {
  21         void (*func)(void *), *arg;
  22         LOCK(lock);
  23         for (; head; head=head->next, slot=COUNT) while(slot-->0) {
  24                 func = head->f[slot];
  25                 arg = head->a[slot];
  26                 UNLOCK(lock);
  27                 func(arg);
  28                 LOCK(lock);
  29         }
  30 }
  31
  32 void __cxa_finalize(void *dso)
  33 {
  34 }
  35
  36 int __cxa_atexit(void (*func)(void *), void *arg, void *dso)
  37 {
  38         LOCK(lock);
  39
  40         /* Defer initialization of head so it can be in BSS */
  41         if (!head) head = &builtin;
  42
  43         /* If the current function list is full, add a new one */
  44         if (slot==COUNT) {
  45                 struct fl *new_fl = calloc(sizeof(struct fl), 1);
  46                 if (!new_fl) {
  47                         UNLOCK(lock);
  48                         return -1;
  49                 }
  50                 new_fl->next = head;
  51                 head = new_fl;
  52                 slot = 0;
  53         }
  54
  55         /* Append function to the list. */
  56         head->f[slot] = func;
  57         head->a[slot] = arg;
  58         slot++;
  59
  60         UNLOCK(lock);
  61         return 0;
  62 }
  63
  64 static void call(void *p)
  65 {
  66         ((void (*)(void))(uintptr_t)p)();
  67 }
  68
  69 int atexit(void (*func)(void))
  70 {
  71         return __cxa_atexit(call, (void *)(uintptr_t)func, 0);
  72 }