为什么我会遇到Linux信号处理的意外行为？(Why am I experiencing unexpected behavior with Linux signal handling?)

 我生活在Win7 / MSVC 2010sp1的环境中，两个不同的Linux盒子（Red Hat）和g ++版本（4.4.7,4.1.2），以及AIX和xlc ++（08.00.0000.0025）。 
 
 不久前，我们要求将一些代码从AIX移到Linux上。 没过多久就看到Linux有点不同了。 通常，当抛出信号时，我们处理它并抛出C ++异常。 这没有按预期工作。 
 
 长话短说，从信号处理程序抛出c ++异常是行不通的。 
 
 过了一段时间，我整理了一个使用setjmp / longjmp将异常移出处理程序的修复程序。 在所有平台上都可以进行后续测试。 经过一场强制性的立方体快乐舞会后，我开始进行一些单元测试。 哎呀。 
 
 我的一些测试在Linux上失败了。 我观察到的是，提升功能只能工作一次。 使用SIGILL进行了两次测试，第一次通过，第二次失败。 我打破了一把斧头，并开始砍掉代码以尽可能多地删除斧头。 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
 
 对于两个Linux盒子，它看起来像这样。 
 
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 **********
 
 所以，我真正的问题是“ 这里发生了什么？ ” 
 
 我的修辞问题是： 
 
 
 
 还有其他人观察到这种行为吗？ 
 
 
 我该怎么做才能解决这个问题？ 
 
 
 我应该注意哪些其他事情？ 
 

I live in an environment with Win7/MSVC 2010sp1, two different Linux boxes (Red Hat) with g++ versions (4.4.7, 4.1.2), and AIX with xlc++ (08.00.0000.0025).
 
Not so long ago it was requested that we move some code from AIX over to Linux. It didn't take too long to see that Linux was a bit different. Normally when a signal is thrown, we handle it and throw a C++ exception. That was not working as expected.
 
Long story short, throwing c++ exceptions from a signal handler isn't going to work.
 
Sometime later, I put together a fix that uses setjmp/longjmp to move the exception out of the handler. Aftersome testing and the dang thing works on all platforms. After an obligatory round of cubical happy dance I moved on to setting up some unit tests. Oops.
 
Some of my tests were failing on Linux. What I observed was that the raise function only worked once. With two tests using SIGILL, the first one passed, and the second one failed. I broke out an axe, and started chopping away at the code to remove as much cruft as possible. That yielded this smaller example.
 
#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;
}
 
For the Windows and the AIX boxes I get the expected output.
 
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
 
For both Linux boxes it looks like this.
 
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 **********
 
So, my real question is "What is going on here?"
 
My retorical questions are:
 
 
 
Is anyone else observing this behavior?
 
 
What should I do to try to troubleshoot this issue?
 
 
What other things should I be aware of?
 

原文：https://stackoverflow.com/questions/28005187