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/* Register destructors for C++ TLS variables declared with thread_local.
Copyright (C) 2013-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<>. */
#include <stdlib.h>
#include <ldsodefs.h>
typedef void (*dtor_func) (void *);
struct dtor_list
dtor_func func;
void *obj;
struct link_map *map;
struct dtor_list *next;
static __thread struct dtor_list *tls_dtor_list;
static __thread void *dso_symbol_cache;
static __thread struct link_map *lm_cache;
/* Register a destructor for TLS variables declared with the 'thread_local'
keyword. This function is only called from code generated by the C++
compiler. FUNC is the destructor function and OBJ is the object to be
passed to the destructor. DSO_SYMBOL is the __dso_handle symbol that each
DSO has at a unique address in its map, added from crtbegin.o during the
linking phase. */
__cxa_thread_atexit_impl (dtor_func func, void *obj, void *dso_symbol)
/* Prepend. */
struct dtor_list *new = calloc (1, sizeof (struct dtor_list));
new->func = func;
new->obj = obj;
new->next = tls_dtor_list;
tls_dtor_list = new;
/* See if we already encountered the DSO. */
__rtld_lock_lock_recursive (GL(dl_load_lock));
if (__glibc_unlikely (dso_symbol_cache != dso_symbol))
ElfW(Addr) caller = (ElfW(Addr)) dso_symbol;
struct link_map *l = _dl_find_dso_for_object (caller);
/* If the address is not recognized the call comes from the main
program (we hope). */
lm_cache = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded;
/* A destructor could result in a thread_local construction and the former
could have cleared the flag. */
if (lm_cache->l_type == lt_loaded && lm_cache->l_tls_dtor_count == 0)
lm_cache->l_flags_1 |= DF_1_NODELETE;
new->map = lm_cache;
__rtld_lock_unlock_recursive (GL(dl_load_lock));
return 0;
/* Call the destructors. This is called either when a thread returns from the
initial function or when the process exits via the exit function. */
__call_tls_dtors (void)
while (tls_dtor_list)
struct dtor_list *cur = tls_dtor_list;
tls_dtor_list = tls_dtor_list->next;
cur->func (cur->obj);
__rtld_lock_lock_recursive (GL(dl_load_lock));
/* Allow DSO unload if count drops to zero. */
if (cur->map->l_tls_dtor_count == 0 && cur->map->l_type == lt_loaded)
cur->map->l_flags_1 &= ~DF_1_NODELETE;
__rtld_lock_unlock_recursive (GL(dl_load_lock));
free (cur);
libc_hidden_def (__call_tls_dtors)
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