1  /* Copyright (C) 1999-2023 Free Software Foundation, Inc.
       2  
       3     NOTE: This source is derived from an old version taken from the GNU C
       4     Library (glibc).
       5  
       6  This file is part of GCC.
       7  
       8  GCC is free software; you can redistribute it and/or modify it under
       9  the terms of the GNU General Public License as published by the Free
      10  Software Foundation; either version 3, or (at your option) any later
      11  version.
      12  
      13  GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      14  WARRANTY; without even the implied warranty of MERCHANTABILITY or
      15  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      16  for more details.
      17  
      18  Under Section 7 of GPL version 3, you are granted additional
      19  permissions described in the GCC Runtime Library Exception, version
      20  3.1, as published by the Free Software Foundation.
      21  
      22  You should have received a copy of the GNU General Public License and
      23  a copy of the GCC Runtime Library Exception along with this program;
      24  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      25  <http://www.gnu.org/licenses/>.  */
      26  
      27  #include <assert.h>
      28  #include <stdlib.h>
      29  
      30  #include "exit.h"
      31  
      32  #undef __cxa_atexit
      33  
      34  #define atomic_write_barrier() __asm__ ("eieio" ::: "memory")
      35  
      36  int
      37  attribute_hidden
      38  __internal_atexit (void (*func) (void *), void *arg, void *d,
      39  		   struct exit_function_list **listp)
      40  {
      41    struct exit_function *new = __new_exitfn (listp);
      42  
      43    if (new == NULL)
      44      return -1;
      45  
      46  #ifdef PTR_MANGLE
      47    PTR_MANGLE (func);
      48  #endif
      49    new->func.cxa.fn = (void (*) (void *, int)) func;
      50    new->func.cxa.arg = arg;
      51    new->func.cxa.dso_handle = d;
      52    atomic_write_barrier ();
      53    new->flavor = ef_cxa;
      54    return 0;
      55  }
      56  
      57  
      58  /* Register a function to be called by exit or when a shared library
      59     is unloaded.  This function is only called from code generated by
      60     the C++ compiler.  */
      61  int
      62  __cxa_atexit (void (*func) (void *), void *arg, void *d)
      63  {
      64    return __internal_atexit (func, arg, d, &__exit_funcs);
      65  }
      66  INTDEF(__cxa_atexit)
      67  
      68  
      69  static struct exit_function_list initial;
      70  struct exit_function_list *__exit_funcs = &initial;
      71  uint64_t __new_exitfn_called;
      72  
      73  struct exit_function *
      74  __new_exitfn (struct exit_function_list **listp)
      75  {
      76    struct exit_function_list *p = NULL;
      77    struct exit_function_list *l;
      78    struct exit_function *r = NULL;
      79    size_t i = 0;
      80  
      81    for (l = *listp; l != NULL; p = l, l = l->next)
      82      {
      83        for (i = l->idx; i > 0; --i)
      84  	if (l->fns[i - 1].flavor != ef_free)
      85  	  break;
      86  
      87        if (i > 0)
      88  	break;
      89  
      90        /* This block is completely unused.  */
      91        l->idx = 0;
      92      }
      93  
      94    if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
      95      {
      96        /* The last entry in a block is used.  Use the first entry in
      97  	 the previous block if it exists.  Otherwise create a new one.  */
      98        if (p == NULL)
      99  	{
     100  	  assert (l != NULL);
     101  	  p = (struct exit_function_list *)
     102  	    calloc (1, sizeof (struct exit_function_list));
     103  	  if (p != NULL)
     104  	    {
     105  	      p->next = *listp;
     106  	      *listp = p;
     107  	    }
     108  	}
     109  
     110        if (p != NULL)
     111  	{
     112  	  r = &p->fns[0];
     113  	  p->idx = 1;
     114  	}
     115      }
     116    else
     117      {
     118        /* There is more room in the block.  */
     119        r = &l->fns[i];
     120        l->idx = i + 1;
     121      }
     122  
     123    /* Mark entry as used, but we don't know the flavor now.  */
     124    if (r != NULL)
     125      {
     126        r->flavor = ef_us;
     127        ++__new_exitfn_called;
     128      }
     129  
     130    return r;
     131  }