c++qtqstringbad-alloc

Crash in QString toUtf8()

I have a slot:

void Foo::func(QString str1, const QString& str2, int width, int height)
{
    std::unique_lock<std::mutex> _lock(m_mutex);

#ifdef _DEBUG
    MEMORYSTATUSEX statex;
    statex.dwLength = sizeof (statex);
    if (GlobalMemoryStatusEx(&statex)) {
        qDebug() << QString("There are %1 free MB of physical memory.\n").arg(statex.ullAvailPhys / 1024 / 1024);
    }
#endif

    BaseClass::someFunc(
        str1.toStdString(),
        str2.toUtf8().constData(),
        width,
        height
    );
}

It seems to be correct and it works. But if program works for a long time (night for example) it crashes in this function at line

str2.toUtf8().constData()

I first thought that this is a thread-based error, but my lock didn't work. All the local variables and class members are ok. The crash error is:

First-chance exception at 0x76E45B68 foo.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x00EFC6EC

But from the code above last MEMORYSTATUSEX show that available memory is 

There are 2314 free MB of physical memory

I also thought that str2 is too big, but it works fine with length of 49152, 168441 etc. What is the problem? Did I miss something?

Stack Trace:

    KernelBase.dll!_RaiseException@16()    Unknown
[External Code] 
Qt5Cored.dll!qBadAlloc() Line 2849  C++
Qt5Cored.dll!QByteArray::QByteArray(int size, Qt::Initialization __formal) Line 1409    C++
Qt5Cored.dll!QUtf8::convertFromUnicode(const QChar * uc, int len) Line 151  C++
Qt5Cored.dll!QString::toUtf8_helper(const QString & str) Line 4373  C++
Qt5Cored.dll!QString::toUtf8() Line 56  C++
foo.exe!Foo::func(QString str1, const QString & str2, int width, int height) Line 3600  C++
foo.exe!Foo::qt_static_metacall(QObject * _o, QMetaObject::Call _c, int _id, void * * _a) Line 1126 C++
Qt5Cored.dll!QMetaObject::activate(QObject * sender, int signalOffset, int local_signal_index, void * * argv) Line 3717 C++
Qt5Cored.dll!QMetaObject::activate(QObject * sender, const QMetaObject * m, int local_signal_index, void * * argv) Line 3582    C++
foo.exe!SomeClass::func(QString _t1, const QString & _t2, int _t3, int _t4) Line 137    C++
foo.exe!SomeClass::qt_static_metacall(QObject * _o, QMetaObject::Call _c, int _id, void * * _a) Line 81 C++
Qt5Cored.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 485   C++
Qt5Cored.dll!QObject::event(QEvent * e) Line 1246   C++
Qt5Widgetsd.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3720    C++
Qt5Widgetsd.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3164  C++
Qt5Cored.dll!QCoreApplication::notifyInternal(QObject * receiver, QEvent * event) Line 935  C++
Qt5Cored.dll!QCoreApplication::sendEvent(QObject * receiver, QEvent * event) Line 228   C++
Qt5Cored.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1552    C++
Qt5Cored.dll!QCoreApplication::sendPostedEvents(QObject * receiver, int event_type) Line 1410   C++
qwindowsd.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 81    C++
Qt5Cored.dll!qt_internal_proc(HWND__ * hwnd, unsigned int message, unsigned int wp, long lp) Line 414   C++
[External Code] 
Qt5Cored.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 807    C++
qwindowsd.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 73   C++
Qt5Cored.dll!QEventLoop::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 129   C++
Qt5Cored.dll!QEventLoop::exec(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 204    C++
Qt5Cored.dll!QCoreApplication::exec() Line 1188 C++
Qt5Guid.dll!QGuiApplication::exec() Line 1508   C++
Qt5Widgetsd.dll!QApplication::exec() Line 2957  C++
foo.exe!WinMain(HINSTANCE__ * __formal, HINSTANCE__ * __formal, char * lpCmdLine, int __formal) Line 348    C++
[External Code]

Thanks in advance!

Solution

  • For those who, like me, just stumbled on this thread because they wanted to convert a QString into a char * with a call to str.toUtf8().constData() or str.toUtf8().data(), but that was leading a program to crash or to throw an exception like EXC_BAD_ACCESS on XCode, here's the answer: