Windows: QProcess::waitForFinished not returning after timeout

QProcess::waitForFinished() does never return, even if a timeout is set.

This is reproducable when cancelling an ongoing build using mingw32-make inside Qt Creator: Qt Creator will first send a Ctrl-C command (which usually breaks mignw32-make , even if executed with cmd.exe). Then it will call

m_process->waitForFinished(5000);

in AbstractProcessStep::checkForCancel(). However, this call will never return. Adding log statements to qprocess_win.cpp shows that the "forever" loop in static bool drainOutputPipes(QProcessPrivate *d) is never exited.