Qt5.12.1 - Linux/gcc_64 - "QTemporaryFile->open()" needs the help of a workaround...

From the documentation: "QTemporaryFile is used to create unique temporary files safely. The file itself is created by calling open()."

Being on "Ubuntu 16.04.5 LTS 64-Bit" with ".../Qt5.12.1/5.12.1/gcc_64/" "QTemporaryFile->open()" does not open the file ==> "QTemporaryFile->exists() == false".
Placing "(void) QTemporaryFile->fileName()" right under "QTemporaryFile->open()", triggers the opening of the file ==> "QTemporaryFile->exists() == true".

Identical source code without the workaround: "(void) QTemporaryFile->fileName()" works nicely on e.g. Windows7 and the latest OSX.

The last Qt version without the above behavior is Qt5.12.0.

Btw...: Same behavior in case the "QTemporaryFile" is not a pointer...

Extracted source code:

class webGate: public QNetworkAccessManager

{ Q_OBJECT public: webGate(QObject * parent = 0); ~webGate(); // ... private: QTemporaryFile *currentQTemporaryFile; }

;

webGate::webGate(QObject * parent) :
QNetworkAccessManager(parent)

{ // ... currentQTemporaryFile = new QTemporaryFile(this); // ... }

void webGate::resultExtraction() {
// ...
if (currentQTemporaryFile->exists())

{ // ... }

else {
if (currentQTemporaryFile->open()) {
#ifdef _linux_
if (!currentQTemporaryFile->exists())

{ (void) currentQTemporaryFile->fileName(); // Currently necessary workaround on Linux/Qt5.12.1 ... }

else

{ qDebug().noquote().nospace() << __FILE__ << ":" << QString::number(__LINE__) << "\tOPENED \"QTemporaryFile\" WITHOUT \"EXISTENCE CHECK WORKAROUND\" ON LINUX...!\n"; }

#endif
#if defined(_APPLE_) || defined(_WIN32)
if (!currentQTemporaryFile->exists())

{ (void) currentQTemporaryFile->fileName(); // Not necessary on Windows/OSX/Qt5.12.1 ... qDebug().noquote().nospace() << __FILE__ << ":" << QString::number(__LINE__) << "\tHAD TO USE \"EXISTENCE CHECK WORKAROUND\" TO OPEN \"QTemporaryFile\" ON WINDOWS OR ON OSX...!\n"; }

#endif
} else

{ qDebug().noquote().nospace() << __FILE__ << ":" << QString::number(__LINE__) << "\tCOULD NOT OPEN \"QTemporaryFile\"...!\n"; }

// ...
}
// ...
}