Export __cxa_thread_atexit_impl as an alias for __cxa_thread_atexit.

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

lib/libc/include/libc_private.h

@@ -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

lib/libc/stdlib/Makefile.inc

@@ -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 \

lib/libc/stdlib/Symbol.map

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

lib/libc/stdlib/cxa_thread_atexit.c

@@ -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));
+	return (__cxa_thread_atexit_hidden(dtor_func, obj, dso_symbol));
-	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);
-	}
 }

lib/libc/stdlib/cxa_thread_atexit_impl.c

@@ -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);
+	}
+}