From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-486368-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 75751 invoked by alias); 15 May 2015 17:40:57 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
Received: (qmail 75569 invoked by uid 48); 15 May 2015 17:40:53 -0000
From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/66146] call_once not C++11-compliant on ppc64le
Date: Fri, 15 May 2015 17:40:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 5.1.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: msebor at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution:
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-66146-4-KGDCncRNF5@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-66146-4@http.gcc.gnu.org/bugzilla/>
References: <bug-66146-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2015-05/txt/msg01208.txt.bz2

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66146

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
On Power, both glibc and AIX pthread_once behave the same way: i.e., they fail
to clear the once flag on exception.  The test case below mimics glibc's
pthread_once and demonstrates the root cause of the problem: the cancellation
handler is not invoked when an exception is thrown unless the
pthread_cleanup_push/pop macros are compiled in C++ code. Simply recompiling
glibc's pthread_once.c using a C++ compiler (and adding the apprpriate extern
"C" decoration) should fix it.

Until it's fixed, as a workaround, it seems that libstdc++ could clear the flag
when an exception is thrown before propagating it out of call_once.

$ cat t.c && gcc -O2 -Wall -c -fasynchronous-unwind-tables -g t.c && g++ -DMAIN
-O2 -Wall t.o -pthread t.c && ./a.out 
#include <pthread.h>
#include <stdio.h>

extern int n;

#if MAIN

extern "C" void foo () { throw 0; }
extern "C" void bar (void (*)());

int main () {
    try {
        bar (foo);
    }
    catch (...) {
        printf ("caught exception: pthread cleanup handler %sinvoked\n",
                n ? "" : "not ");
    }

    return n == 1 ? 0 : 1;
}

#else

int n;
#if __cplusplus
extern "C" {
#endif

static void cleanup (void *arg) { ++n; }

void bar (void (*pf)(void)) {
    pthread_cleanup_push (cleanup, 0);
    pf ();
    pthread_cleanup_pop (0);
}

#if __cplusplus
}
#endif

#endif
caught exception: pthread cleanup handler not invoked