#include <mutex>
#include <iostream>
 
void f(bool doThrow) {
    if (doThrow) {
        std::cout << "Throwing" << std::endl;
        throw 42;
    }
    std::cout << "Not throwing" << std::endl;
}
 
std::once_flag flag;
 
void g(bool doThrow) {
    try {
        std::call_once(flag,f,doThrow);
        std::cout << "Returning" << std::endl;
    } catch (int i) {
        std::cout << "Caught " << i << std::endl;
    }
}
 
int main() {
    std::once_flag flag;
    g(true);
    g(true);
    g(false);
    g(true);
    g(false);
}

当编译g -std = c 11 -pthread -ggdb时,我得到输出：

Throwing
Caught 42

之后进程挂起：

#0  0x000003fff7277abf in futex_wait (private=0,expected=1,futex_word=0x2aaaacad144 <flag>) at ../sysdeps/unix/sysv/linux/futex-internal.h:61
#1  futex_wait_simple (private=0,futex_word=0x2aaaacad144 <flag>) at ../sysdeps/nptl/futex-internal.h:135
#2  __pthread_once_slow (once_control=0x2aaaacad144 <flag>,init_routine=0x3fff7a8d870 <std::__once_proxy()>) at pthread_once.c:105
#3  0x000002aaaaaab06f in __gthread_once (__once=0x2aaaacad144 <flag>,__func=0x3fff7a8d870 <std::__once_proxy()>) at /usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/include/g++-v5/x86_64-pc-linux-gnu/bits/gthr-default.h:699
#4  0x000002aaaaaab6c8 in std::call_once<void (&)(bool),bool&> (__once=...,__f=@0x2aaaaaab08c: {void (bool)} 0x2aaaaaab08c <f(bool)>) at /usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/include/g++-v5/mutex:738
#5  0x000002aaaaaab192 in g (doThrow=true) at test.cpp:17
#6  0x000002aaaaaab287 in main () at test.cpp:27

但是当编译时使用clang -std = c 11 -pthread -ggdb我得到：

Throwing
Caught 42
Throwing
Caught 42
Not throwing
Returning
Returning
Returning

据我所知,这似乎是正确的行为.

这是GCC错误,只是我对std :: call_once的语义感到困惑,还是我的代码不正确？