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From: "andrey.vul at gmail dot com" <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 15:12:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66146

--- Comment #2 from Andrey V <andrey.vul at gmail dot com> ---
Replacing throw/try/catch with longjmp/setjmp for non-returning function exit,
like so:

#include <stdio.h>
#include <pthread.h>
#include <setjmp.h>

pthread_once_t flag_ = PTHREAD_ONCE_INIT;

int call_count = 0;
jmp_buf catch_;

void func_() {
  printf("Inside func_ call_count %d\n", call_count);
  if (++call_count < 2)
        longjmp(catch_, 1);
}
int main() {
  int signo;
  printf("Before calling call_once flag_: %d\n", *(int*)&flag_);
  signo = setjmp(catch_);
  if (!signo)
    pthread_once(&flag_, func_);
  else
    printf("Inside catch all excepton flag_: %d\n", *(int*)&flag_);
  printf("before the 2nd call to call_once flag_: %d\n", *(int*)&flag_);
  pthread_once(&flag_, func_);
}

, the invalid behavior isn't triggered.
It appears that pthread_once doesn't take kindly to exceptions in the
once_func.