[CMake] QT4_WRAP_CPP and Implicit Dependencies

[Miller, Frank]

Greetings,

Suppose we have a header file, Dum.h, that is included by another header
file, Main.h, and Main.h needs to be processed with the qt moc tool.
When Dum.h changes, should we rerun moc on Main.h?

QMake says yes. CMake, using QT4_WRAP_CPP, says no.

I am inclined to believe qmake on this one. However, I have yet to think
of a way to break a build by not rerunning moc. Is this a problem?

Please pardon me if you think this question is in the wrong forum. I am
asking here because I know there are a lot of qt users in this community
and qmake is clearly not doing anything wrong.

Here is a simple example:

    === CMakeLists.txt ===
    cmake_minimum_required( VERSION 2.8.0 )
    project( mocdep )
    find_package( Qt4 REQUIRED )
    include( ${QT_USE_FILE} )
    include_directories( ${CMAKE_BINARY_DIR} )
    QT4_WRAP_CPP( mocdep_MOCSOURCES Main.h )
    add_executable( mocdep Main.cpp ${mocdep_MOCSOURCES} Main.h )
    target_link_libraries( mocdep ${QT_QTCORE_LIBRARY} ${QT_QTGUI_LIBRARY} )

    === mocdep.pro ===
    HEADERS = Main.h Dum.h
    SOURCES = Main.cpp

    === Dum.h ===
    #pragma once

    === Main.h ===
    #pragma once
    #include "Dum.h"
    #include <QMainWindow>

    class MainWindow : public QMainWindow
    {
        Q_OBJECT
    };

    === Main.cpp ===
    #include "Main.h"
    #include <QApplication>

    int main( int argc, char * argv[] )
    {
        QApplication app(argc, argv);

        MainWindow mainWindow;
        mainWindow.show();

        return app.exec();
    }

Frank

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