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Export __cxa_thread_atexit_impl as an alias for __cxa_thread_atexit.

Browse Source 
libstdc++ before gcc r244057 expected that libc provided
__cxa_thread_atexit_impl, and libstdc++ implemented
__cxa_thread_atexit, by forwarding the calls to _impl.  Mentioned gcc
revision checks for __cxa_thread_atexit in libc and does not provide
the symbol from libstdc++ if found.

This change helps older gcc, in particular, all released versions
which implement thread_local, by consolidating the implementation into
libc.  For that versions, if configured with the current libc, the
__cxa_thread_atexit is exported from libstdc++ as a trivial wrapper
around libc::__cxa_thread_atexit_impl.

The __cxa_thread_atexit implementation is put into separate source
file to allow for static linking with older libstdc++.a.

gcc bugzilla:	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78968
Reported by:	Hannes Hauswedell <h2+fbsdports@fsfe.org>
PR:	215709
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2017-01-07 16:05:19 +00:00
parent 1c1cb6e087
commit b7c7684ae2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=311651
5 changed files with 164 additions and 106 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
lib/libc/include/libc_private.h
View File

@ -272,6 +272,8 @@ void _malloc_thread_cleanup(void);
* thread is exiting, so its thread-local dtors should be called.
*/
void __cxa_thread_call_dtors(void);
int __cxa_thread_atexit_hidden(void (*dtor_func)(void *), void *obj,
void *dso_symbol) __hidden;
/*
* These functions are used by the threading libraries in order to protect

4
lib/libc/stdlib/Makefile.inc
View File

@ -5,7 +5,9 @@
.PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/stdlib ${LIBC_SRCTOP}/stdlib
MISRCS+=C99_Exit.c a64l.c abort.c abs.c atexit.c atof.c atoi.c atol.c atoll.c \
bsearch.c cxa_thread_atexit.c div.c exit.c getenv.c getopt.c getopt_long.c \
bsearch.c \
cxa_thread_atexit.c cxa_thread_atexit_impl.c \
div.c exit.c getenv.c getopt.c getopt_long.c \
getsubopt.c hcreate.c hcreate_r.c hdestroy_r.c heapsort.c heapsort_b.c \
hsearch_r.c imaxabs.c imaxdiv.c \
insque.c l64a.c labs.c ldiv.c llabs.c lldiv.c lsearch.c \

1
lib/libc/stdlib/Symbol.map
View File

@ -118,6 +118,7 @@ FBSD_1.4 {
FBSD_1.5 {
__cxa_thread_atexit;
__cxa_thread_atexit_impl;
};
FBSDprivate_1.0 {

110
lib/libc/stdlib/cxa_thread_atexit.c
View File

@ -1,7 +1,10 @@
/*-
* Copyright (c) 2016 Mahdi Mokhtari <mokhi64@gmail.com>
* Copyright (c) 2017 The FreeBSD Foundation
* All rights reserved.
*
* Portions of this software were developed by Konstantin Belousov
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
@ -27,114 +30,11 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/queue.h>
#include "namespace.h"
#include <errno.h>
#include <link.h>
#include <pthread.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include "un-namespace.h"
#include "libc_private.h"
/*
* C++11 introduces the thread_local scope (like __thread with some
* additions). As a key-feature it should support non-trivial
* destructors, registered with __cxa_thread_atexit() to be executed
* at the thread termination.
*
* The implemention keeps a _Thread_local list of destructors per each
* thread, and calls __cxa_thread_call_dtors() on each thread's exit
* to do cleanup. For a thread calling exit(3), in particular, for
* the initial thread returning from main(), we call
* __cxa_thread_call_dtors() inside exit().
*
* It could be possible that a dynamically loaded library, use
* thread_local variable but is dlclose()'d before thread exit. The
* destructor of this variable will then try to access the address,
* for calling it but it's unloaded, so it'll crash. We're using
* __elf_phdr_match_addr() to detect and prevent such cases and so
* prevent the crash.
*/
#define CXA_DTORS_ITERATIONS 4
struct cxa_thread_dtor {
void *obj;
void (*func)(void *);
void *dso;
LIST_ENTRY(cxa_thread_dtor) entry;
};
static _Thread_local LIST_HEAD(dtor_list, cxa_thread_dtor) dtors =
LIST_HEAD_INITIALIZER(dtors);
int
__cxa_thread_atexit(void (*dtor_func)(void *), void *obj, void *dso_symbol)
{
struct cxa_thread_dtor *new_dtor;
new_dtor = malloc(sizeof(*new_dtor));
if (new_dtor == NULL) {
errno = ENOMEM; /* forcibly override malloc(3) error */
return (-1);
}
new_dtor->obj = obj;
new_dtor->func = dtor_func;
new_dtor->dso = dso_symbol;
LIST_INSERT_HEAD(&dtors, new_dtor, entry);
return (0);
}
static void
walk_cb_call(struct cxa_thread_dtor *dtor)
{
struct dl_phdr_info phdr_info;
if (_rtld_addr_phdr(dtor->dso, &phdr_info) &&
__elf_phdr_match_addr(&phdr_info, dtor->func))
dtor->func(dtor->obj);
else
fprintf(stderr, "__cxa_thread_call_dtors: dtr %p from "
"unloaded dso, skipping\n", (void *)(dtor->func));
}
static void
walk_cb_nocall(struct cxa_thread_dtor *dtor __unused)
{
}
static void
cxa_thread_walk(void (*cb)(struct cxa_thread_dtor *))
{
struct cxa_thread_dtor *dtor, *tdtor;
LIST_FOREACH_SAFE(dtor, &dtors, entry, tdtor) {
LIST_REMOVE(dtor, entry);
cb(dtor);
free(dtor);
}
}
/*
* This is the callback function we use to call destructors, once for
* each thread. It is called in exit(3) in libc/stdlib/exit.c and
* before exit_thread() in libthr/thread/thr_exit.c.
*/
void
__cxa_thread_call_dtors(void)
{
int i;
for (i = 0; i < CXA_DTORS_ITERATIONS && !LIST_EMPTY(&dtors); i++)
cxa_thread_walk(walk_cb_call);
if (!LIST_EMPTY(&dtors)) {
fprintf(stderr, "Thread %p is exiting with more "
"thread-specific dtors created after %d iterations "
"of destructor calls\n",
_pthread_self(), i);
cxa_thread_walk(walk_cb_nocall);
}
return (__cxa_thread_atexit_hidden(dtor_func, obj, dso_symbol));
}

153
lib/libc/stdlib/cxa_thread_atexit_impl.c Normal file
View File

@ -0,0 +1,153 @@
/*-
* Copyright (c) 2016 Mahdi Mokhtari <mokhi64@gmail.com>
* Copyright (c) 2016, 2017 The FreeBSD Foundation
* All rights reserved.
*
* Portions of this software were developed by Konstantin Belousov
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/queue.h>
#include "namespace.h"
#include <errno.h>
#include <link.h>
#include <pthread.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include "un-namespace.h"
#include "libc_private.h"
/*
* C++11 introduces the thread_local scope (like __thread with some
* additions). As a key-feature it should support non-trivial
* destructors, registered with __cxa_thread_atexit() to be executed
* at the thread termination.
*
* The implemention keeps a _Thread_local list of destructors per each
* thread, and calls __cxa_thread_call_dtors() on each thread's exit
* to do cleanup. For a thread calling exit(3), in particular, for
* the initial thread returning from main(), we call
* __cxa_thread_call_dtors() inside exit().
*
* It could be possible that a dynamically loaded library, use
* thread_local variable but is dlclose()'d before thread exit. The
* destructor of this variable will then try to access the address,
* for calling it but it's unloaded, so it'll crash. We're using
* __elf_phdr_match_addr() to detect and prevent such cases and so
* prevent the crash.
*/
#define CXA_DTORS_ITERATIONS 4
struct cxa_thread_dtor {
void *obj;
void (*func)(void *);
void *dso;
LIST_ENTRY(cxa_thread_dtor) entry;
};
static _Thread_local LIST_HEAD(dtor_list, cxa_thread_dtor) dtors =
LIST_HEAD_INITIALIZER(dtors);
int
__cxa_thread_atexit_impl(void (*dtor_func)(void *), void *obj,
void *dso_symbol)
{
return (__cxa_thread_atexit_hidden(dtor_func, obj, dso_symbol));
}
int
__cxa_thread_atexit_hidden(void (*dtor_func)(void *), void *obj,
void *dso_symbol)
{
struct cxa_thread_dtor *new_dtor;
new_dtor = malloc(sizeof(*new_dtor));
if (new_dtor == NULL) {
errno = ENOMEM; /* forcibly override malloc(3) error */
return (-1);
}
new_dtor->obj = obj;
new_dtor->func = dtor_func;
new_dtor->dso = dso_symbol;
LIST_INSERT_HEAD(&dtors, new_dtor, entry);
return (0);
}
static void
walk_cb_call(struct cxa_thread_dtor *dtor)
{
struct dl_phdr_info phdr_info;
if (_rtld_addr_phdr(dtor->dso, &phdr_info) &&
__elf_phdr_match_addr(&phdr_info, dtor->func))
dtor->func(dtor->obj);
else
fprintf(stderr, "__cxa_thread_call_dtors: dtr %p from "
"unloaded dso, skipping\n", (void *)(dtor->func));
}
static void
walk_cb_nocall(struct cxa_thread_dtor *dtor __unused)
{
}
static void
cxa_thread_walk(void (*cb)(struct cxa_thread_dtor *))
{
struct cxa_thread_dtor *dtor, *tdtor;
LIST_FOREACH_SAFE(dtor, &dtors, entry, tdtor) {
LIST_REMOVE(dtor, entry);
cb(dtor);
free(dtor);
}
}
/*
* This is the callback function we use to call destructors, once for
* each thread. It is called in exit(3) in libc/stdlib/exit.c and
* before exit_thread() in libthr/thread/thr_exit.c.
*/
void
__cxa_thread_call_dtors(void)
{
int i;
for (i = 0; i < CXA_DTORS_ITERATIONS && !LIST_EMPTY(&dtors); i++)
cxa_thread_walk(walk_cb_call);
if (!LIST_EMPTY(&dtors)) {
fprintf(stderr, "Thread %p is exiting with more "
"thread-specific dtors created after %d iterations "
"of destructor calls\n",
_pthread_self(), i);
cxa_thread_walk(walk_cb_nocall);
}
}