MessageBox with MinWG
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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)?
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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.
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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?
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Is renaming my MessageBox class the only way out here?
no, this is exactly the reason namespaces were invented
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Yes, of course! Didn't think about that. I am still too much of a C++ novice...
Solved :)
