src/exit/atexit.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include "libc.h"
   4 #include "lock.h"
   5 #include "fork_impl.h"
   6
   7 #define malloc __libc_malloc
   8 #define calloc __libc_calloc
   9 #define realloc undef
  10 #define free undef
  11
  12 /* Ensure that at least 32 atexit handlers can be registered without malloc */
  13 #define COUNT 32
  14
  15 static struct fl
  16 {
  17         struct fl *next;
  18         void (*f[COUNT])(void *);
  19         void *a[COUNT];
  20 } builtin, *head;
  21
  22 static int slot;
  23 static volatile int lock[1];
  24 volatile int *const __atexit_lockptr = lock;
  25
  26 void __funcs_on_exit()
  27 {
  28         void (*func)(void *), *arg;
  29         LOCK(lock);
  30         for (; head; head=head->next, slot=COUNT) while(slot-->0) {
  31                 func = head->f[slot];
  32                 arg = head->a[slot];
  33                 UNLOCK(lock);
  34                 func(arg);
  35                 LOCK(lock);
  36         }
  37 }
  38
  39 void __cxa_finalize(void *dso)
  40 {
  41 }
  42
  43 int __cxa_atexit(void (*func)(void *), void *arg, void *dso)
  44 {
  45         LOCK(lock);
  46
  47         /* Defer initialization of head so it can be in BSS */
  48         if (!head) head = &builtin;
  49
  50         /* If the current function list is full, add a new one */
  51         if (slot==COUNT) {
  52                 struct fl *new_fl = calloc(sizeof(struct fl), 1);
  53                 if (!new_fl) {
  54                         UNLOCK(lock);
  55                         return -1;
  56                 }
  57                 new_fl->next = head;
  58                 head = new_fl;
  59                 slot = 0;
  60         }
  61
  62         /* Append function to the list. */
  63         head->f[slot] = func;
  64         head->a[slot] = arg;
  65         slot++;
  66
  67         UNLOCK(lock);
  68         return 0;
  69 }
  70
  71 static void call(void *p)
  72 {
  73         ((void (*)(void))(uintptr_t)p)();
  74 }
  75
  76 int atexit(void (*func)(void))
  77 {
  78         return __cxa_atexit(call, (void *)(uintptr_t)func, 0);
  79 }