What is the difference between configuring QT with -no-exceptions and -DQT_NO_EXCEPTIONS?

Dmitriano

What is the difference between -no-exceptions and -DQT_NO_EXCEPTIONS? And what is right way to get rid of “try { } catch (…) {}” in qtbase\src\corelib\thread\qthread_unix.cpp?

void *QThreadPrivate::start(void *arg)
{
#if !defined(Q_OS_ANDROID)
    pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
#endif
    pthread_cleanup_push(QThreadPrivate::finish, arg);

#ifndef QT_NO_EXCEPTIONS
    try
#endif
    {
        QThread *thr = reinterpret_cast<QThread *>(arg);
        QThreadData *data = QThreadData::get2(thr);

        {
            QMutexLocker locker(&thr->d_func()->mutex);

            // do we need to reset the thread priority?
            if (int(thr->d_func()->priority) & ThreadPriorityResetFlag) {
                thr->d_func()->setPriority(QThread::Priority(thr->d_func()->priority & ~ThreadPriorityResetFlag));
            }

            data->threadId.store(to_HANDLE(pthread_self()));
            set_thread_data(data);

            data->ref();
            data->quitNow = thr->d_func()->exited;
        }

        if (data->eventDispatcher.load()) // custom event dispatcher set?
            data->eventDispatcher.load()->startingUp();
        else
            createEventDispatcher(data);

#if (defined(Q_OS_LINUX) || defined(Q_OS_MAC) || defined(Q_OS_QNX))
        {
            // sets the name of the current thread.
            QString objectName = thr->objectName();

            pthread_t thread_id = from_HANDLE<pthread_t>(data->threadId.load());
            if (Q_LIKELY(objectName.isEmpty()))
                setCurrentThreadName(thread_id, thr->metaObject()->className());
            else
                setCurrentThreadName(thread_id, objectName.toLocal8Bit());
        }
#endif

        emit thr->started(QThread::QPrivateSignal());
#if !defined(Q_OS_ANDROID)
        pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
        pthread_testcancel();
#endif
        thr->run();
    }
#ifndef QT_NO_EXCEPTIONS
#ifdef __GLIBCXX__
    // POSIX thread cancellation under glibc is implemented by throwing an exception
    // of this type. Do what libstdc++ is doing and handle it specially in order not to
    // abort the application if user's code calls a cancellation function.
    catch (const abi::__forced_unwind &) {
        throw;
    }
#endif // __GLIBCXX__
    catch (...) {
        qTerminate();
    }
#endif // QT_NO_EXCEPTIONS

I tried to build QT/Android on Windows with -DQT_NO_EXCEPTIONS, but got the following error:

....\include\QtXmlPatterns\5.11.1\QtXmlPatterns/private/../../../../../src/xmlpatterns/utils/qpatternistlocale_p.h:275:2: error: #error "Patternist uses exceptions and cannot be built without."

SGaist

Hi,

IIRC, the former will trigger the generation the latter. If you don't use it, you can also skip building the QtXmlPatterns module.

Dmitriano

@SGaist Hi!

I built QT without QtXmlPatterns, but it is not clear enough what to use -no-exceptions or -DQT_NO_EXCEPTIONS.

SGaist

AFAIK -no-exceptions when configuring Qt and QT_NO_EXCEPTIONS when you want to be able to provide both version within your code.

Dmitriano

@SGaist I succeeded with QT_NO_EXCEPTIONS, now there is no "try {} catch (...)" in qtbase\src\corelib\thread\qthread_unix.cpp, but If I do

configure.bat -prefix C:\Qt\Qt5.11-Android -no-exceptions -release -force-debug-info -platform win32-g++ -opengl es2 -xplatform android-g++ -android-ndk C:\Users\D-Ef\AppData\Local\Android\Sdk\ndk-bundle -android-sdk C:\Users\D-Ef\AppData\Local\Android\Sdk -opensource -confirm-license -nomake tests -nomake examples

with QT 5.11.1, I get:

ERROR: Unknown command line option '-no-exceptions'.

SGaist

Getting old... I forgot that it was an option for Qt 4 when not all compilers supported exceptions which is not the case anymore.