libc-top-half/musl/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
  24 #if defined(__wasilibc_unmodified_upstream) || defined(_REENTRANT)
  25 static volatile int lock[1];
  26 volatile int *const __atexit_lockptr = lock;
  27 #endif
  28
  29 void __funcs_on_exit()
  30 {
  31         void (*func)(void *), *arg;
  32         LOCK(lock);
  33         for (; head; head=head->next, slot=COUNT) while(slot-->0) {
  34                 func = head->f[slot];
  35                 arg = head->a[slot];
  36                 UNLOCK(lock);
  37                 func(arg);
  38                 LOCK(lock);
  39         }
  40 }
  41
  42 void __cxa_finalize(void *dso)
  43 {
  44 }
  45
  46 int __cxa_atexit(void (*func)(void *), void *arg, void *dso)
  47 {
  48         LOCK(lock);
  49
  50         /* Defer initialization of head so it can be in BSS */
  51         if (!head) head = &builtin;
  52
  53         /* If the current function list is full, add a new one */
  54         if (slot==COUNT) {
  55                 struct fl *new_fl = calloc(sizeof(struct fl), 1);
  56                 if (!new_fl) {
  57                         UNLOCK(lock);
  58                         return -1;
  59                 }
  60                 new_fl->next = head;
  61                 head = new_fl;
  62                 slot = 0;
  63         }
  64
  65         /* Append function to the list. */
  66         head->f[slot] = func;
  67         head->a[slot] = arg;
  68         slot++;
  69
  70         UNLOCK(lock);
  71         return 0;
  72 }
  73
  74 static void call(void *p)
  75 {
  76         ((void (*)(void))(uintptr_t)p)();
  77 }
  78
  79 int atexit(void (*func)(void))
  80 {
  81         return __cxa_atexit(call, (void *)(uintptr_t)func, 0);
  82 }