CMake building precompiled headers can't find Qt stuff

Perdrix

2>1>
2>Building Custom Rule C:/Users/amonra/Documents/GitHub/DSS/DeepSkyStacker/CMakeLists.txt
2>cmake_pch.cxx
2>C:\Users\amonra\Documents\GitHub\DSS\DeepSkyStacker\stdafx.h(3,10): error C1083: Cannot open include file: 'QtWidgets': No such file or directory
2>(compiling source file 'CMakeFiles/DeepSkyStacker.dir/cmake_pch.cxx')
2>Done building project "DeepSkyStacker.vcxproj" -- FAILED.

I did:

find_package(Qt6 6.8 REQUIRED COMPONENTS Gui Widgets Network Charts)
qt_standard_project_setup()

So thought that the Qt include dirs would be searched.

What have I missed?

Perdrix

I finally discovered that the includes for Qt are added when you do (for example):

target_link_libraries(DeepSkyStacker PRIVATE
    Qt6::Widgets
    Qt6::Network
   :

which is not at all obvious - once I added that, it worked.

Christian Ehrlicher

@Perdrix said in CMake building precompiled headers can't find Qt stuff:

What have I missed?

At least the part on where you create the pch in the CMakeLists.txt

https://cmake.org/cmake/help/latest/command/target_precompile_headers.html

Perdrix

Err no that was in the CMakeLists.txt file otherwise CMake would not have created the cmake_pch.cxx file:

target_precompile_headers(DeepSkyStacker PRIVATE
	stdafx.h
	)

It's the failure to find the Qt headers I am concerned about.

Christian Ehrlicher

Since you as always fail to provide a minimal, compilable example - this works fine for me:

find_package(Qt6 COMPONENTS Widgets REQUIRED)
add_executable(TestApp
    main.cpp
)
target_link_libraries(TestApp PRIVATE Qt6::Widgets)
target_precompile_headers(TestApp PRIVATE pre.h)

pre.h contains

#include <QDialog>

Perdrix

If I knew how to create a minimal example in this case I would have done so - its not for lack of trying.
I have specified:

################################################################################
# Include directories
################################################################################
target_include_directories(DeepSkyStacker PUBLIC
    ${CMAKE_CURRENT_SOURCE_DIR}/.
    ${CMAKE_CURRENT_SOURCE_DIR}/../DeepSkyStackerKernel
    ${CMAKE_CURRENT_SOURCE_DIR}/GeneratedFiles/$<CONFIG>
    ${CMAKE_CURRENT_SOURCE_DIR}/GeneratedFiles
    ${CMAKE_CURRENT_SOURCE_DIR}/../LibRaw
    ${CMAKE_CURRENT_SOURCE_DIR}/../ZCLass
    ${CMAKE_CURRENT_SOURCE_DIR}/../Tools
    ${CMAKE_CURRENT_SOURCE_DIR}/../LibTiff
    ${CMAKE_CURRENT_SOURCE_DIR}/../CFitsIO
    ${CMAKE_CURRENT_SOURCE_DIR}/../Zlib
    $ENV{Boost_1_80_0}
	"$<$<CONFIG:Debug>:C:/Program Files (x86)/Visual Leak Detector/include>"
)

to pick up my own include directories. If by doing that I have wiped out the ones set by:

find_package(Qt6 6.8 REQUIRED COMPONENTS Gui Widgets Network Charts)
qt_standard_project_setup()

then I may have done that wrong - I thought target_include_directories appended to the ones already set, if not, how do I change that to append to the ones set by the Qt stuff.

D.

Perdrix

I finally discovered that the includes for Qt are added when you do (for example):

target_link_libraries(DeepSkyStacker PRIVATE
    Qt6::Widgets
    Qt6::Network
   :

which is not at all obvious - once I added that, it worked.

Christian Ehrlicher

@Perdrix said in CMake building precompiled headers can't find Qt stuff:

I finally discovered that the includes for Qt

That's not related to Qt but how imported targets in usually cmake work.

Perdrix

YOU may know that, but a new user of CMake wouldn't be expected to.

Christian Ehrlicher

Not that in the Qt documentation of every class is written on how to use the Qt libs...
https://doc.qt.io/qt-6/qwidget.html

CMake:	find_package(Qt6 REQUIRED COMPONENTS Widgets)
target_link_libraries(mytarget PRIVATE Qt6::Widgets)

Perdrix

I fail to see the relevance of that remark - the point I was making is that it is totally counter-intuitive that target_link_libraries(Qt6::Widgets) should add include directories for the compilation.