MessageBox with MinWG

[ModelTech]

I created a subclass MessageBox of QMessageBox that has some static functions, including one named error. Using these functions elsewhere gives a compilation error with MinWG but not with gcc. The error looks a bit odd:

error: undefined reference to `MessageBoxW::error(QString const&, QString const&, QFlags<QMessageBox::StandardButton>, QWidget*)'

The oddity for me is in the letter W after MessageBox in the reference. When diving into this, I found that there is a global #define in winuser.h as follows:

#define MessageBox __MINGW_NAME_AW(MessageBox)

which already claims the MessageBox symbol. Replacing the above code in winuser.h into for example

#define MINWGMessageBox __MINGW_NAME_AW(MessageBox)

solves my compilation problem and the application runs correctly.

Has anyone encountered this problem before? Is it save to fix the problem in winuser.h or should I better rename my class (not really my preference)?

[SGaist]

Hi and welcome to devnet,

No it's not safe to fiddle with winuser.h. See here for more information about the MessageBox macro.

Short version: MessageBox is a Windows API wrapped in a macro by MinGW to get the correct function.

[ModelTech]

That's what I guessed as well...

Now, I got the opportunity to use the msvc2012 compiler for the same code which also gives a compiler error, with a similar oddity

mainwindow.obj:-1: error: LNK2019: unresolved external symbol "public: static int __cdecl MessageBoxW::error(class QString const &,class QString const &,class QFlags<enum QMessageBox::StandardButton>,class QWidget *)" (?error@MessageBoxW@@SAHABVQString@@0V?$QFlags@W4StandardButton@QMessageBox@@@@PAVQWidget@@@Z) referenced in function "private: void __thiscall MainWindow::openFile(void)" (?openFile@MainWindow@@AAEXXZ)

Is renaming my MessageBox class the only way out here?

[VRonin]

Is renaming my MessageBox class the only way out here?

no, this is exactly the reason namespaces were invented

[ModelTech]

Yes, of course! Didn't think about that. I am still too much of a C++ novice...

Solved :)