Handling memory exhausted in Windows Qt app - c++

Question

My application can use a lot of memory and I want to be able to handle running out of memory gracefully. So I do this:
bool Application::notify( QObject* receiver, QEvent* event )
{
bool done = true;
try
{
done = QApplication::notify( receiver, event );
}
catch ( std::bad_alloc& ex )
{
releaseMemory();
qWarning() << "bad_alloc exception: " << ex.what();
m_outOfMemoryDlg->exec();
exit( 1 );
}
catch ( const std::exception& ex )
{
releaseMemory();
qWarning() << "exception: " << ex.what();
criticalMessage( nullptr, QString( "%1 has to close due to an exception. Please contact support." ).arg( APP_NAME ) );
exit( 2 );
}
catch ( ... )
{
releaseMemory();
qWarning() << "exception";
criticalMessage( nullptr, QString( "%1 has to close. Please contact support." ).arg( APP_NAME ) );
exit( 3 );
}
return done;
}
Where m_outOfMemoryDlg is a QDialog with a helpful message I create and hide at startup. This all works fine on macOS. I get a std::bad_alloc exception, the QDialog appears and the program shuts gracefully. But on Windows the whole OS just locks. The screen is frozen and I have to power off and back on to make it responsive.
In my .pro file I added:
CONFIG += exceptions
win32 {
QMAKE_CXXFLAGS_EXCEPTIONS_ON = /EHa
QMAKE_CXXFLAGS_STL_ON = /EHa
}
I also added:
#ifdef Q_OS_WIN
#include <new.h>
LONG WINAPI
exceptionFilter( struct _EXCEPTION_POINTERS* exceptionInfo )
{
if ( exceptionInfo )
{
EXCEPTION_RECORD* er = exceptionInfo->ExceptionRecord;
if ( er )
{
qWarning() << "Windows exception: " << er->ExceptionCode;
}
}
exit( 4 );
return EXCEPTION_EXECUTE_HANDLER;
}
int outOfMemory( size_t )
{
qWarning() << "Out of memory";
exit( 5 );
return 0;
}
#endif
Application::Application( int& argc, char** argv )
: QApplication( argc, argv )
{
#ifdef Q_OS_WIN
SetUnhandledExceptionFilter( exceptionFilter );
_set_new_handler( outOfMemory );
#endif
...
}
As per https://www.codeproject.com/Articles/207464/Exception-Handling-in-Visual-Cplusplus . Still no luck. Any ideas?
I am using Qt 5.15.2 on Windows 10.