11
鉴于这段代码:的std :: call_once的()挂在第二个电话后可赎回扔在第一次调用
#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g++ -std=c++11 -pthread -ggdb
编译我得到的输出:
Throwing
Caught 42
之后该进程挂起:
#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, expected=1, 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=..., [email protected]: {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。
这是一个海湾合作委员会的bug,只是我对std::call_once
的语义困惑,或者是我的代码不正确?
'gcc'和'g ++'不是一回事! –
复制,看起来像一个错误。 –
@ Meninx-メネンックス所以呢?一个是另一个的一部分。 – user2079303