Wie man Strg+C unter Windows und Linux mit Qt abfängt

Ich verwende diese Klasse, um Signale in C++-Konsolenanwendungen abzufangen. Es ist jedoch nicht spezifisch für Qt. Es verwendet SetConsoleCtrlHandler() auf Windows-Plattformen und Funktionen, die von auf anderen Plattformen bereitgestellt werden. Das Knifflige daran ist, dass "Signal" kein plattformübergreifender Begriff ist - Windows und POSIX haben unterschiedliche Definitionen dafür. Jedenfalls versucht diese Klasse, sie einem gemeinsamen Vokabular zuzuordnen. Strg^C lässt sich gut auf beiden Plattformen abbilden.

Ich hoffe, dass dies an Ihre spezifische Situation angepasst werden kann. Bitte beachten Sie, dass die Fehlerprüfung minimal ist und wahrscheinlich verbessert werden sollte.

Verwendung (main.cpp)

#include "SignalHandler.h"

class Application : public SignalHandler
{
public:
    Application() : SignalHandler(SignalHandler::SIG_INT), myThread(NULL) {}

    int Application::main(int argc, char *argv[])
    {
        // Main program instructions here (e.g. start a thread)
        myThread = new Thread(...);
        myThread->start();
        myThread->join();
        delete myThread;
        return 0;
    }

    bool handleSignal(int signal)
    {
        std::cout << "Handling signal " << signal << std::endl;
        if (_myThread && _myThread->isRunning())
        {
            _myThread->stop();
            // The thread is going to stop soon, so don't propagate this signal further
            return true;
        }
        // Let the signal propagate as though we had not been there
        return false;
    }
private:
    Thread* myThread;
};

int main(int argc, char* argv[])
{
    Application app;
    return app.main(argc, argv);
}

SignalHandler.h

class SignalHandler 
{
public:
    SignalHandler(int mask = DEFAULT_SIGNALS);
    virtual ~SignalHandler();

    enum SIGNALS
    {
        SIG_UNHANDLED   = 0,    // Physical signal not supported by this class
        SIG_NOOP        = 1,    // The application is requested to do a no-op (only a target that platform-specific signals map to when they can't be raised anyway)
        SIG_INT         = 2,    // Control+C (should terminate but consider that it's a normal way to do so; can delay a bit)
        SIG_TERM        = 4,    // Control+Break (should terminate now without regarding the consquences)
        SIG_CLOSE       = 8,    // Container window closed (should perform normal termination, like Ctrl^C) [Windows only; on Linux it maps to SIG_TERM]
        SIG_RELOAD      = 16,   // Reload the configuration [Linux only, physical signal is SIGHUP; on Windows it maps to SIG_NOOP]
        DEFAULT_SIGNALS = SIG_INT | SIG_TERM | SIG_CLOSE,
    };
    static const int numSignals = 6;

    virtual bool handleSignal(int signal) = 0;

private:
    int _mask;
};

SignalHandler.cpp

#include "SignalHandler.h"
#include <assert.h>

#ifndef _WIN32

#include <signal.h>

#else

#include <windows.h>

#endif //!_WIN32

// There can be only ONE SignalHandler per process
SignalHandler* g_handler(NULL);

#ifdef _WIN32

BOOL WINAPI WIN32_handleFunc(DWORD);
int WIN32_physicalToLogical(DWORD);
DWORD WIN32_logicalToPhysical(int);
std::set<int> g_registry;

#else //_WIN32

void POSIX_handleFunc(int);
int POSIX_physicalToLogical(int);
int POSIX_logicalToPhysical(int);

#endif //_WIN32

SignalHandler::SignalHandler(int mask) : _mask(mask)
{
    assert(g_handler == NULL);
    g_handler = this;

#ifdef _WIN32
    SetConsoleCtrlHandler(WIN32_handleFunc, TRUE);
#endif //_WIN32

    for (int i=0;i<numSignals;i++)
    {
        int logical = 0x1 << i;
        if (_mask & logical)
        {
#ifdef _WIN32
            g_registry.insert(logical);
#else
            int sig = POSIX_logicalToPhysical(logical);
            bool failed = signal(sig, POSIX_handleFunc) == SIG_ERR;
            assert(!failed);
            (void)failed; // Silence the warning in non _DEBUG; TODO: something better

#endif //_WIN32
        }
    }

}

SignalHandler::~SignalHandler()
{
#ifdef _WIN32
    SetConsoleCtrlHandler(WIN32_handleFunc, FALSE);
#else
    for (int i=0;i<numSignals;i++)
    {
        int logical = 0x1 << i;
        if (_mask & logical)
        {
            signal(POSIX_logicalToPhysical(logical), SIG_DFL);
        }
    }
#endif //_WIN32
}


#ifdef _WIN32
DWORD WIN32_logicalToPhysical(int signal)
{
    switch (signal)
    {
    case SignalHandler::SIG_INT: return CTRL_C_EVENT;
    case SignalHandler::SIG_TERM: return CTRL_BREAK_EVENT;
    case SignalHandler::SIG_CLOSE: return CTRL_CLOSE_EVENT;
    default: 
        return ~(unsigned int)0; // SIG_ERR = -1
    }
}
#else
int POSIX_logicalToPhysical(int signal)
{
    switch (signal)
    {
    case SignalHandler::SIG_INT: return SIGINT;
    case SignalHandler::SIG_TERM: return SIGTERM;
    // In case the client asks for a SIG_CLOSE handler, accept and
    // bind it to a SIGTERM. Anyway the signal will never be raised
    case SignalHandler::SIG_CLOSE: return SIGTERM;
    case SignalHandler::SIG_RELOAD: return SIGHUP;
    default: 
        return -1; // SIG_ERR = -1
    }
}
#endif //_WIN32


#ifdef _WIN32
int WIN32_physicalToLogical(DWORD signal)
{
    switch (signal)
    {
    case CTRL_C_EVENT: return SignalHandler::SIG_INT;
    case CTRL_BREAK_EVENT: return SignalHandler::SIG_TERM;
    case CTRL_CLOSE_EVENT: return SignalHandler::SIG_CLOSE;
    default:
        return SignalHandler::SIG_UNHANDLED;
    }
}
#else
int POSIX_physicalToLogical(int signal)
{
    switch (signal)
    {
    case SIGINT: return SignalHandler::SIG_INT;
    case SIGTERM: return SignalHandler::SIG_TERM;
    case SIGHUP: return SignalHandler::SIG_RELOAD;
    default:
        return SignalHandler::SIG_UNHANDLED;
    }
}
#endif //_WIN32



#ifdef _WIN32
BOOL WINAPI WIN32_handleFunc(DWORD signal)
{
    if (g_handler)
    {
        int signo = WIN32_physicalToLogical(signal);
        // The std::set is thread-safe in const reading access and we never
        // write to it after the program has started so we don't need to 
        // protect this search by a mutex
        std::set<int>::const_iterator found = g_registry.find(signo);
        if (signo != -1 && found != g_registry.end())
        {
            return g_handler->handleSignal(signo) ? TRUE : FALSE;
        }
        else
        {
            return FALSE;
        }
    }
    else
    {
        return FALSE;
    }
}
#else
void POSIX_handleFunc(int signal)
{
    if (g_handler)
    {
        int signo = POSIX_physicalToLogical(signal);
        g_handler->handleSignal(signo);
    }
}
#endif //_WIN32