fail to use Q_OBJECT Macro in CMake Project

Sewing

I am having trouble with the meta Object Compiler of Qt in my CMake Project. A shared lib I am building contains the following code and employs the pimpl idiom. After invoking CMake and upon compilation I get

AUTOGEN: error: ~/tools/Project/gui/src/mainWindow.cpp: The file contains a Q_OBJECT macro, but does not include "mainWindow.moc" ! gui/CMakeFiles/gui_automoc.dir/build.make:57: recipe for target 'gui/CMakeFiles/gui_automoc' failed make[2]: *** [gui/CMakeFiles/gui_automoc] Error 1 CMakeFiles/Makefile2:234: recipe for target 'gui/CMakeFiles/gui_automoc.dir/all' failed

I dont get what I am doing wrong or whats the correct way to incorporate src files with the Q_OBJECT Macro in my project.

Please help =/

gui/src/mainWindow.hpp


#include <QMainWindow>
#include <string>


class MainWindow : public QMainWindow {
  class MainWindowImpl;

 public:
  MainWindow(QWidget* parent = nullptr);

 private:
  MainWindowImpl* pimpl_;
};
gui/include/gui/mainWindow.cpp

#include "gui/mainWindow.hpp"

class MainWindow::MainWindowImpl : public QWidget{
 Q_OBJECT
  public:
   explicit MainWindowImpl(MainWindow *parent);

  private:
   MainWindow &parent_;
};

MainWindow::MainWindowImpl::MainWindowImpl(MainWindow *parent)
    : QWidget{parent}, parent_(*parent) {}

MainWindow::MainWindow(QWidget *parent) : QMainWindow{parent} {
    pimpl_ = new MainWindowImpl{this};
    setCentralWidget(pimpl_);
}

I compile the library like so:

cmake_minimum_required(VERSION 3.5.1 FATAL_ERROR)
project(gui)

add_library(${PROJECT_NAME}
  SHARED
   src/mainWindow.cpp
)
add_library(gui::gui ALIAS ${PROJECT_NAME})

target_include_directories(${PROJECT_NAME} 
  PUBLIC 
   ${PROJECT_SOURCE_DIR}/include
)

set_target_properties(${PROJECT_NAME} PROPERTIES AUTOMOC TRUE)

target_link_libraries(${PROJECT_NAME}
  PUBLIC
   Qt5::Widgets
   Qt5::Core
   Qt5::Xml
   Qt5::OpenGL
   Qt5::Gui
)

install(TARGETS ${PROJECT_NAME} DESTINATION lib)

Now I want to link this lib against my executable

apps/main.cpp

#include <QApplication>
#include "gui/mainWindow.hpp"

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

QApplication app{argc, argv};

MainWindow gui{};
gui.show();

return app.exec();
}

with the following CMakelists.txt where I link against the gui lib

cmake_minimum_required (VERSION 3.5.1 FATAL_ERROR)
project (app)

add_executable(${PROJECT_NAME}
  main.cpp
)

target_include_directories(${PROJECT_NAME}
    PUBLIC ${PROJECT_BINARY_DIR}
)

target_link_libraries(${PROJECT_NAME}
  PRIVATE
   gui::gui
   Qt5::Widgets
   Qt5::Core
   Qt5::Xml
   Qt5::OpenGL
   Qt5::Gui
 )

 install(TARGETS ${PROJECT_NAME}
         DESTINATION bin)

my top-level CMakeLists of the project looks like the following

cmake_minimum_required (VERSION 3.5.1 FATAL_ERROR)
project(project)

set(CMAKE_INSTALL_DIR ${PROJECT_SOURCE_DIR}/obj)
set(CMAKE_INSTALL_PREFIX  ${CMAKE_INSTALL_DIR})
# add our local path to the runtime path
SET(CMAKE_INSTALL_RPATH "$ORIGIN:${CMAKE_INSTALL_PREFIX}/lib")
# also add the link paths to the runtime paths
SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)

find_package(Qt5 COMPONENTS Core Widgets Xml OpenGL Gui REQUIRED)

## --> Build libraries and applications  <--
add_subdirectory(gui)
add_subdirectory(apps)

Sewing

Anyone? I am losing my mind over here -.-

? Offline

@Sewing said in fail to use Q_OBJECT Macro in CMake Project:

Anyone?

It's only 2 hours since your initial post. Please show a little more patience, like 24 hours. It's always nighttime for half of the community. And it's friday.

SGaist

Hi,

Did you already took a look at the CMake Manual from Qt's documentation ?

Sewing

I did, but without being able to infer any conclusive hints from the article towards a solution for my problem

VRonin

The problem is not CMake:

@Sewing said in fail to use Q_OBJECT Macro in CMake Project:

mainWindow.cpp: The file contains a Q_OBJECT macro

from http://doc.qt.io/qt-5/moc.html

The moc tool reads a C++ header file.

Did you declare a class with Q_OBJECT in a .cpp file? if so either yo do as the compiler tells you and #include "mainWindow.moc" (this file name might change depending on how moc gets invoked) at the end of the file or, as I would recommend, move it into a header

Sewing

Mh difficult since I employ the pimpl idiom in which the nested implementation class in defined entirely within the source file

SGaist

Then move the private declaration part in its own header that you only include in the implementation part.

Note that your MainWindow implementation looks a bit convoluted, you might be over-engineering some things.

Sewing

thank you for the help.

you mean cuz of using pimpl? this is just a minimal example and my intention was, to keep the public interface of mainwindow.cpp quite clean and readable

VRonin

@Sewing said in fail to use Q_OBJECT Macro in CMake Project:

pimpl idiom in which the nested implementation class in defined entirely within the source file

You can move it into a header file, Qt does it all the time, they use _p.h suffix to mark private headers. For example: QDateTimePrivate

Sewing

so if I understood correctly, the reason of having to do this is that the Q_OBJECT Macro has to be defined in the header file instead of the source file?

and after doing so, is the line

set_target_properties(${PROJECT_NAME} PROPERTIES AUTOMOC TRUE)

sufficient for invoking the MOC in my CMakeLists file?

VRonin

@SGaist said in fail to use Q_OBJECT Macro in CMake Project:

Did you already took a look at the CMake Manual from Qt's documentation ?

@Sewing said in fail to use Q_OBJECT Macro in CMake Project:

I did

from http://doc.qt.io/qt-5/cmake-manual.html:

# Instruct CMake to run moc automatically when needed.
set(CMAKE_AUTOMOC ON)

Sewing

I read that, just thought variables in CMake are old-style while target_properties are the modern way to handle things

VRonin

I heard opposing arguments to that when it comes to moc/rcc/uic. Personally, I use the set(CMAKE_AUTOMOC ON) way