[SOLVED] Preprocessor division by zero while evaluating `QT

Preprocessor division by zero while evaluating `QT_CONFIG(printer)`

Compiling with g++ (from Makefile generated with qmake) using the line

#if !QT_CONFIG(printer)
    // do something
#endif

gives a preprocessor error on both g++ (7.3.0)

test.cpp:25:6: error: division by zero in #if
 #if !QT_CONFIG(printer)

and clang (6.00)

test.cpp:25:6: error: division by zero in preprocessor expression
#if !QT_CONFIG(printer)
     ^~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/qt5/QtCore/qglobal.h:84:30: note: expanded from macro 'QT_CONFIG'
#define QT_CONFIG(feature) (1/QT_FEATURE_##feature == 1)
                            ~^~~~~~~~~~~~~~~~~~~~~
1 error generated.

where clang++ gives the more detailed output. printer is not enabled, thus the macro as recommended to do conditional compilation. The QT version is 5.9.5. Any suggestions (wrong usage?) appreciated.

Solution

I don't think you should focus on that macro. The point of that macro is to simply crash your compilation code when QT_FEATURE_printer is zero. The code was not designed to work otherwise.

Instead of using the macro conditionally try to find out why QT_FEATURE_printer is zero and include / configure dependencies to change that (it seems to be definend in printsupport/qtprintsupport-config.h).