我所处的环境是Win7 / MSVC 2010sp1,带有g版本(4.4.7、4.1.2)的两个不同的Linux盒(Red Hat)以及带有xlc(08.00.0000.0025)的AIX.

不久前,有人要求我们将一些代码从AIX移到Linux.不久之后,Linux便有所不同.通常,当信号被抛出时,我们处理它并抛出一个C异常.那没有按预期工作.

Long story short, throwing c++ exceptions from a signal handler isn’t going to work.

稍后,我整理了一个使用setjmp / longjmp的修复程序,以将异常移出处理程序.经过一些测试和验证,该功能适用​​于所有平台.经过强制性的三次欢乐舞蹈之后,我继续进行一些单元测试.哎呀.

我的一些测试在Linux上失败了.我观察到的是,raise函数仅工作一次.使用SIGILL进行了两次测试,第一个通过了,第二次失败了.我打开了一个斧头,开始砍掉代码以消除尽可能多的麻烦.这产生了这个较小的例子.

#include <csetjmp>
#include <iostream>
#include <signal.h>

jmp_buf  mJmpBuf;
jmp_buf *mpJmpBuf = &mJmpBuf;
int status = 0;
int testCount = 3;

void handler(int signalNumber)
{
    signal(signalNumber, handler);
    longjmp(*mpJmpBuf, signalNumber);
}

int main(void)
{
    if (signal(SIGILL, handler) != SIG_ERR)
    {
        for (int test = 1; test <= testCount; test++)
        {
            try
            {
                std::cerr << "Test " << test << "\n";
                if ((status = setjmp(*mpJmpBuf)) == 0)
                {
                    std::cerr << "    About to raise SIGILL" << "\n";
                    int returnStatus = raise(SIGILL);
                    std::cerr << "    Raise returned value " << returnStatus
                              << "\n";
                }
                else
                {
                    std::cerr << "    Caught signal. Converting signal "
                              << status << " to exception" << "\n";
                    std::exception e;
                    throw e;
                }
                std::cerr << "    SIGILL should have been thrown **********\n";
            }
            catch (std::exception &)
            { std::cerr << "    Caught exception as expected\n"; }
        }
    }
    else
    { std::cerr << "The signal handler wasn't registered\n"; }

    return 0;
}

对于Windows和AIX框,我得到了预期的输出.

Test 1
    About to raise SIGILL
    Caught signal. Converting signal 4 to exception
    Caught exception as expected Test 2
    About to raise SIGILL
    Caught signal. Converting signal 4 to exception
    Caught exception as expected Test 3
    About to raise SIGILL
    Caught signal. Converting signal 4 to exception
    Caught exception as expected

对于这两个Linux机器,它看起来都是这样.

Test 1
    About to raise SIGILL
    Caught signal. Converting signal 4 to exception
    Caught exception as expected
Test 2
    About to raise SIGILL
    Raise returned value 0
    SIGILL should have been thrown **********
Test 3
    About to raise SIGILL
    Raise returned value 0
    SIGILL should have been thrown **********

因此,我真正的问题是“这是怎么回事？”

我的反驳问题是：

>是否有人在观察这种行为？
>我该怎么做才能解决此问题？
>我还应该注意什么？

解决方法:

您必须使用sigsetjmp / siglongjmp来确保混合信号和跳跃时的正确行为.如果更改代码,它将在Linux下正常工作.

您还使用了不推荐的旧信号API.我鼓励您使用更可靠的签名接口.第一个好处是您不再需要重置处理程序中的信号捕获…