stdlib/exit.c

   1 /* Copyright (C) 1991-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include <sysdep.h>
  22 #include <libc-lock.h>
  23 #include "exit.h"
  24
  25 #include "set-hooks.h"
  26 DEFINE_HOOK (__libc_atexit, (void))
  27
  28 /* Initialize the flag that indicates exit function processing
  29    is complete. See concurrency notes in stdlib/exit.h where
  30    __exit_funcs_lock is declared.  */
  31 bool __exit_funcs_done = false;
  32
  33 /* Call all functions registered with `atexit' and `on_exit',
  34    in the reverse of the order in which they were registered
  35    perform stdio cleanup, and terminate program execution with STATUS.  */
  36 void
  37 attribute_hidden
  38 __run_exit_handlers (int status, struct exit_function_list **listp,
  39                      bool run_list_atexit, bool run_dtors)
  40 {
  41   /* First, call the TLS destructors.  */
  42 #ifndef SHARED
  43   if (&__call_tls_dtors != NULL)
  44 #endif
  45     if (run_dtors)
  46       __call_tls_dtors ();
  47
  48   __libc_lock_lock (__exit_funcs_lock);
  49
  50   /* We do it this way to handle recursive calls to exit () made by
  51      the functions registered with `atexit' and `on_exit'. We call
  52      everyone on the list and use the status value in the last
  53      exit (). */
  54   while (true)
  55     {
  56       struct exit_function_list *cur = *listp;
  57
  58       if (cur == NULL)
  59         {
  60           /* Exit processing complete.  We will not allow any more
  61              atexit/on_exit registrations.  */
  62           __exit_funcs_done = true;
  63           break;
  64         }
  65
  66       while (cur->idx > 0)
  67         {
  68           struct exit_function *const f = &cur->fns[--cur->idx];
  69           const uint64_t new_exitfn_called = __new_exitfn_called;
  70
  71           switch (f->flavor)
  72             {
  73               void (*atfct) (void);
  74               void (*onfct) (int status, void *arg);
  75               void (*cxafct) (void *arg, int status);
  76               void *arg;
  77
  78             case ef_free:
  79             case ef_us:
  80               break;
  81             case ef_on:
  82               onfct = f->func.on.fn;
  83               arg = f->func.on.arg;
  84 #ifdef PTR_DEMANGLE
  85               PTR_DEMANGLE (onfct);
  86 #endif
  87               /* Unlock the list while we call a foreign function.  */
  88               __libc_lock_unlock (__exit_funcs_lock);
  89               onfct (status, arg);
  90               __libc_lock_lock (__exit_funcs_lock);
  91               break;
  92             case ef_at:
  93               atfct = f->func.at;
  94 #ifdef PTR_DEMANGLE
  95               PTR_DEMANGLE (atfct);
  96 #endif
  97               /* Unlock the list while we call a foreign function.  */
  98               __libc_lock_unlock (__exit_funcs_lock);
  99               atfct ();
 100               __libc_lock_lock (__exit_funcs_lock);
 101               break;
 102             case ef_cxa:
 103               /* To avoid dlclose/exit race calling cxafct twice (BZ 22180),
 104                  we must mark this function as ef_free.  */
 105               f->flavor = ef_free;
 106               cxafct = f->func.cxa.fn;
 107               arg = f->func.cxa.arg;
 108 #ifdef PTR_DEMANGLE
 109               PTR_DEMANGLE (cxafct);
 110 #endif
 111               /* Unlock the list while we call a foreign function.  */
 112               __libc_lock_unlock (__exit_funcs_lock);
 113               cxafct (arg, status);
 114               __libc_lock_lock (__exit_funcs_lock);
 115               break;
 116             }
 117
 118           if (__glibc_unlikely (new_exitfn_called != __new_exitfn_called))
 119             /* The last exit function, or another thread, has registered
 120                more exit functions.  Start the loop over.  */
 121             continue;
 122         }
 123
 124       *listp = cur->next;
 125       if (*listp != NULL)
 126         /* Don't free the last element in the chain, this is the statically
 127            allocate element.  */
 128         free (cur);
 129     }
 130
 131   __libc_lock_unlock (__exit_funcs_lock);
 132
 133   if (run_list_atexit)
 134     RUN_HOOK (__libc_atexit, ());
 135
 136   _exit (status);
 137 }
 138
 139
 140 void
 141 exit (int status)
 142 {
 143   __run_exit_handlers (status, &__exit_funcs, true, true);
 144 }
 145 libc_hidden_def (exit)