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),以及带有xlc ++的AIX(08.00.0000.0025)。
不久前,我们要求将一些代码从AIX移到Linux上。看起来Linux有点不同,并没有花太长时间。通常,当抛出信号时,我们处理它并抛出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,我整理了一个修复程序,它使用setjmp / longjmp将异常移出处理程序。在所有平台上都可以进行后续测试。经过一轮强制性的立体舞蹈之后,我开始进行一些单元测试。糟糕。
我的一些测试在Linux上失败了。我观察到的是,加强功能只能工作一次。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
对于这两个Linux盒子,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 **********
所以,我真正的问题是&#34; 这里发生了什么?&#34;
我的修辞问题是:
答案 0 :(得分:3)
您必须使用sigsetjmp
/ siglongjmp
来确保混合信号和跳转时的正确行为。如果您更改了代码,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sigaction
界面。第一个好处是你不再需要重置处理程序中的信号捕获...