libgcc/config/rs6000/cxa_atexit.c

/* Copyright (C) 1999-2023 Free Software Foundation, Inc.

   NOTE: This source is derived from an old version taken from the GNU C
   Library (glibc).

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <stdlib.h>

#include "exit.h"

#undef __cxa_atexit

#define atomic_write_barrier() __asm__ ("eieio" ::: "memory")

int
attribute_hidden
__internal_atexit (void (*func) (void *), void *arg, void *d,
		   struct exit_function_list **listp)
{
  struct exit_function *new = __new_exitfn (listp);

  if (new == NULL)
    return -1;

#ifdef PTR_MANGLE
  PTR_MANGLE (func);
#endif
  new->func.cxa.fn = (void (*) (void *, int)) func;
  new->func.cxa.arg = arg;
  new->func.cxa.dso_handle = d;
  atomic_write_barrier ();
  new->flavor = ef_cxa;
  return 0;
}


/* Register a function to be called by exit or when a shared library
   is unloaded.  This function is only called from code generated by
   the C++ compiler.  */
int
__cxa_atexit (void (*func) (void *), void *arg, void *d)
{
  return __internal_atexit (func, arg, d, &__exit_funcs);
}
INTDEF(__cxa_atexit)


static struct exit_function_list initial;
struct exit_function_list *__exit_funcs = &initial;
uint64_t __new_exitfn_called;

struct exit_function *
__new_exitfn (struct exit_function_list **listp)
{
  struct exit_function_list *p = NULL;
  struct exit_function_list *l;
  struct exit_function *r = NULL;
  size_t i = 0;

  for (l = *listp; l != NULL; p = l, l = l->next)
    {
      for (i = l->idx; i > 0; --i)
	if (l->fns[i - 1].flavor != ef_free)
	  break;

      if (i > 0)
	break;

      /* This block is completely unused.  */
      l->idx = 0;
    }

  if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
    {
      /* The last entry in a block is used.  Use the first entry in
	 the previous block if it exists.  Otherwise create a new one.  */
      if (p == NULL)
	{
	  assert (l != NULL);
	  p = (struct exit_function_list *)
	    calloc (1, sizeof (struct exit_function_list));
	  if (p != NULL)
	    {
	      p->next = *listp;
	      *listp = p;
	    }
	}

      if (p != NULL)
	{
	  r = &p->fns[0];
	  p->idx = 1;
	}
    }
  else
    {
      /* There is more room in the block.  */
      r = &l->fns[i];
      l->idx = i + 1;
    }

  /* Mark entry as used, but we don't know the flavor now.  */
  if (r != NULL)
    {
      r->flavor = ef_us;
      ++__new_exitfn_called;
    }

  return r;
}