Handling segmentation fault in a program ran from QProcess

Question

I am writing a Qt app to compile and run C++ files. I don't know how can I check for runtime errors such as segmentation fault after the process has been started. I tried using error() signal for reporting runtime error, but it doesn't tell anything about segmentation fault.

//connected to error() signal
void Tester::onError(QProcess::ProcessError e)
{
    switch(e) {
    case QProcess::Crashed:
    case QProcess::WriteError:
    case QProcess::ReadError:
    case QProcess::UnknownError:
        QMessageBox::information(NULL, "Run status", "Runtime error",
                                 QMessageBox::Ok | QMessageBox::Default);
        break;
    default:
        break;
    }
}

This is the file I am testing it with-

#include <iostream>

int main() {
    int *p = NULL;
    *p = 1;  //segmentation fault
    std::cout << *p;
    return 0;
}

When I test the file from the Qt app, the new process runs for about 15-20 seconds and then finished() signal is emitted, with a weird exit code and a message box saying "runtime error". How can I detect that there had been a segmentation fault in the new QProcess so that I can display it to the user?
I am working on Windows 7.

Did you try to connect to `finished(int exitCode, QProcess::ExitStatus exitStatus)` signal and handle `QProcess::ExitStatus` values? — vahancho, Feb 14 '14 at 09:32
@vahancho No I didn't, I thought that would be handled by error() signal. — Shubham, Feb 14 '14 at 09:37
Segmentation faults come from the kernel and not from the process. — dgrat, Feb 14 '14 at 09:44
Ok, so is there a way I can check if the program has segmentation fault? — Shubham, Feb 14 '14 at 09:47
finished(int, QProcess::ExitStatus) should give you QProcess::CrashExit as status. — Frank Osterfeld, Feb 14 '14 at 11:23

score 3 · Answer 1 · answered Feb 14 '14 at 12:17

3

Error reporting with QProcess is a bit confusing - one needs to connect to both error() and finished() to cover all error cases.

If you connect to finished(int exitCode, QProcess::ExitStatus status), a segfault should result in a status of QProcess::CrashExit.

answered Feb 14 '14 at 12:17

Frank Osterfeld

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It kind of does the job, but `QProcess::CrashExit` can be because of other reasons too, so I cannot use it to pin point segfault. – Shubham Feb 14 '14 at 12:22
2

It's detectable at least on Unix. See http://linux.die.net/man/3/wait and WTERMSIG(). Qt uses WIFEXITED() for CrashExit, so it's indeed not sufficient to pinpoint SIGSEGV. But that's a limitation of the QProcess API, not of the OS. – Frank Osterfeld Feb 15 '14 at 08:10

Handling segmentation fault in a program ran from QProcess

1 Answers1