From QMake to CMake. (Different path levels)

Josz

Hi evereyone,

I'm trying to port a multilevel project from QMake to CMake.

Below show I the desired structure:

The location of the root CMakeLists.txt a path level before than the main and the lib is a requirement

├── CMakeLists.txt
├── app02
│   ├── CMakeLists.txt
│   └── main.cpp
└── lib
    ├── CMakeLists.txt
    ├── myprint.cpp
    └── myprint.h

The root CMakeLists.txt is so written:

cmake_minimum_required(VERSION 3.13)

set(CMAKE_PROJECT_NAME "testProject")
project(${CMAKE_PROJECT_NAME})

list(APPEND CMAKE_PREFIX_PATH "/home/enigma/Qt/5.15.2/gcc_64")

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(CMAKE_AUTOMOC ON)
set(CMAKE_INCLUDE_CURRENT_DIR ON)

find_package(Qt5Core REQUIRED)
find_package(Qt5Widgets REQUIRED)

add_subdirectory(lib app02)

set(TARGET "app02Build")
add_executable(${TARGET} ${SOURCES})

target_link_libraries(${TARGET} thePrintLibrary Qt5::Core Qt5::Widgets)

The main.cpp in app002 path is written so:

#include "../lib/myprint.h"

int main(int argc, char *argv[])
{
    myPrint::print("This the second App");
}

And here is its correspondig CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)

set(SOURCES
    main.cpp
)

The lib path contains the next files:

myprint.h

#ifndef MYPRINT_H
#define MYPRINT_H

#include <QDebug>
#include <string>

class myPrint
{
public:
    static void print(std::string toPrint) {
        qDebug() << toPrint.c_str();
    }
};

#endif // MYPRINT_H

myPrint.cpp

#include "myprint.h"
//yes, there is no more code :-)

and the corresponding CMakeLists.txt

cmake_minimum_required(VERSION 3.13)


add_library( 
	thePrintLibrary
	myprint.h
	myprint.cpp
)

The CMake prescan runs fine, but when I compile I become the next error:

[ 28%] Building CXX object app02/CMakeFiles/thePrintLibrary.dir/myprint.cpp.o
In file included from /home/enigma/APD_Programas/Port/test/lib/myprint.cpp:1:
/home/enigma/APD_Programas/Port/test/lib/myprint.h:4:10: fatal error: QDebug: No such file or directory
 #include <QDebug>
          ^~~~~~~~
compilation terminated.
gmake[2]: *** [app02/CMakeFiles/thePrintLibrary.dir/build.make:63: app02/CMakeFiles/thePrintLibrary.dir/myprint.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:162: app02/CMakeFiles/thePrintLibrary.dir/all] Error 2
gmake: *** [Makefile:84: all] Error 2

Someone so kind to help me?

Thanks in advance

Josz

Thank you all,
I found the last fail, with your help.

In that path distribution, I must supply the complete main path in add_executable.

add_executable(${TARGET} app02/main.cpp)

Perhaps is there a better solution, so, if somebody want add something,
please, you're welcomed

Christian Ehrlicher

When you want to use a library you have to link against them. Since QDebug is in QtCore you have to link against QtCore. And since it's in a public header of your lib you have to link use the PUBLIC keyword in target_link_libraries: target_link_libraries(thePrintLibrary PUBLIC Qt5::Core)
See for example the Qt documentation: https://doc.qt.io/qt-6/cmake-manual.html
You also should avoid relative includes but use target_include_directories() instead

Josz

@Christian-Ehrlicher said in From QMake to CMake. (Different path levels):

target_link_libraries(thePrintLibrary PUBLIC Qt5::Core)

Thank you Christian, I did it. I added

target_link_libraries(thePrintLibrary PUBLIC Qt5::Core)

And now I get another error at the end of the link process:

[ 85%] Building CXX object CMakeFiles/app02Build.dir/app02Build_autogen/mocs_compilation.cpp.o
[100%] Linking CXX executable app02Build
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/8/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
gmake[2]: *** [CMakeFiles/app02Build.dir/build.make:88: app02Build] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:74: CMakeFiles/app02Build.dir/all] Error 2
gmake: *** [Makefile:84: all] Error 2

How could I correctly link the main?

Thanks in advance

kkoehne

@Josz said in From QMake to CMake. (Different path levels):

How could I correctly link the main?

I believe that's because you don't list app02/main.cpp in the top-level CMakeLists.txt, but in app02/CMakeLists.txt.

I assume you're trying to mimic qmake's include() behavior here, and expect that set(SOURCES main.cpp) in app02/CMakeLists.txt changes the top-level SOURCES variable. Anyhow, you're using add_subdirectory(), which matches a SUBDIR setup in qmake. If you want _one_project/binary, but want to keep the sources organized in subfolders, use CMake's include().

Josz

Thank you all,
I found the last fail, with your help.

In that path distribution, I must supply the complete main path in add_executable.

add_executable(${TARGET} app02/main.cpp)

Perhaps is there a better solution, so, if somebody want add something,
please, you're welcomed