A cmake project I want to build depends on SDL2, and it comes with the following instruction:
Create a helper called /usr/local/lib/cmake/SDL2/sdl2-config.cmake (because SDL2 doesn't have an SDL2::SDL2 alias) containing:
if(NOT TARGET SDL2::SDL2
AND EXISTS "/usr/lib/x86_64-linux-gnu/cmake/SDL2/sdl2-config.cmake")
include(/usr/lib/x86_64-linux-gnu/cmake/SDL2/sdl2-config.cmake)
add_library(SDL2 SHARED IMPORTED)
set_target_properties(SDL2
PROPERTIES
IMPORTED_LOCATION "${libdir}/libSDL2.so"
INTERFACE_INCLUDE_DIRECTORIES "${SDL2_INCLUDE_DIRS}"
)
add_library(SDL2::SDL2 ALIAS SDL2)
endif()
The problem is that this file isn't found by my cmake (I put a message(...) at the beginning to verify this). If I change the dependency in my CMakeLists.txt from SDL2::SDL2 to just SDL2, it works fine and reads from /usr/lib/x86_64-linux-gnu/cmake/SDL2/sdl2-config.cmake. But this shouldn't be necessary.
How can I get cmake to find this custom file, or how do I find out where to put it?
Related
I have an IMPORTED target which comes from a config package generated by conan. Since conan creates packages for the build type specified in the build_type of the profile, I have added CMAKE_MAP_IMPORTED_CONFIG_DEBUG to Release, so that even if I compile a Debug build of my project, I can still use Config files generated with conan using a Release profile.
This works fine for all the targets in my project. include directories are set correctly, libraries link correctly. except for one case:
I have an INTERFACE target which I use to use only the include directories of an IMPORTED target if one option is set, or use the whole target.
add_library(deTracing INTERFACE)
# Get include directories of Tracy::TracyClient target
get_target_property(TRACY_INCLUDE_DIRECTORIES Tracy::TracyClient INTERFACE_INCLUDE_DIRECTORIES)
# Include the directories unconditionally
target_include_directories(deTracing INTERFACE ${TRACY_INCLUDE_DIRECTORIES})
# Some debug stuff
message(status ${TRACY_INCLUDE_DIRECTORIES})
add_custom_target(genexdebug COMMAND ${CMAKE_COMMAND} -E echo "${TRACY_INCLUDE_DIRECTORIES}")
# If ENABLE_PROFILING is set, link to the library
if(ENABLE_PROFILING)
target_link_libraries(deTracing INTERFACE Tracy::TracyClient)
target_compile_definitions(deTracing INTERFACE ENABLE_PROFILING)
endif()
The issue is that TRACY_INCLUDE_DIRECTORIES is a generator expression with this content
$<$<CONFIG:Release>:/home/seddi/.conan/data/tracy/0.9/_/_/package/913e5b8c3a7b64b23fdaa63b58e3915a742a1112/include>, which is what I can expect, it just contains the include directory for the release config.
But when this expression is evaluated in a Debug build, it just collapses to an empty string, even though I have set the CMAKE_MAP_IMPORTED_CONFIG_DEBUG to Release, so it doesn't set any include directories.
I am out of ideas of how I set the correct INCLUDE_DIRECTORIES to deTracing target.
Edit:
According to CMake, the MAP_IMPORTED_CONFIG_ property is followed when evaluating properties of IMPORTED targets. I have modified deTracing to be an IMPORTED target, yet still doesn't work.
add_library(deTracing INTERFACE IMPORTED)
get_target_property(TRACY_INCLUDE_DIRECTORIES Tracy::TracyClient INTERFACE_INCLUDE_DIRECTORIES)
set_property(
TARGET deTracing
PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${TRACY_INCLUDE_DIRECTORIES}
APPEND) # ${TRACY_INCLUDE_DIRECTORIES})
get_target_property(deTracing_INCLUDE_DIRECTORIES deTracing INTERFACE_INCLUDE_DIRECTORIES)
message("deTracing INCLUDE_DIRECTORIES: ${deTracing_INCLUDE_DIRECTORIES}")
add_library(TestTarget INTERFACE)
target_link_libraries(TestTarget INTERFACE deTracing)
get_target_property(TestTarget_INCLUDE_DIRECTORIES TestTarget INTERFACE_INCLUDE_DIRECTORIES)
message("TestTarget INCLUDE DIRECTORIES: ${TestTarget_INCLUDE_DIRECTORIES}")
This snippet produces the following output
[cmake] deTracing INCLUDE_DIRECTORIES: $<$<CONFIG:Release>:/home/seddi/.conan/data/tracy/0.9/_/_/package/913e5b8c3a7b64b23fdaa63b58e3915a742a1112/include>
[cmake] TestTarget INCLUDE DIRECTORIES: TestTarget_INCLUDE_DIRECTORIES-NOTFOUND
which shows that deTracing is able to set the correct INCLUDE_DIRECTORIES for the Release config, but then is unable to set them on TestTarget, even though deTracing is an IMPORTED target.
I have a directory with various pre-built libraries (mostly headers and libs/dlls, all built without CMake or copied without installing using CMake). For my next project i want to use these libraries with CMake.
I am writing a script that iterates over all the libraries and generates the needed <name>Config.cmake and <name>ConfigVersion.cmake files referencing the existing directory structure.
A minimal config file may look like:
SET(ROOT_DIR_MYLIB "${CMAKE_CURRENT_LIST_DIR}/../../../../MyLib")
add_library(MyLib STATIC IMPORTED)
set_target_properties(MyLib PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "${ROOT_DIR_MYLIB}/include"
IMPORTED_LOCATION "${ROOT_DIR_MYLIB}/Lib/MyLib.lib"
IMPORTED_LOCATION_DEBUG "${ROOT_DIR_MYLIB}/Lib/MyLibd.lib"
)
I have copied the line where the property INTERFACE_INCLUDE_DIRECTORIES is set from another project where this worked, but for some reason it does not for MyLib. When i attempt to include its header files i get compile errors that the include files can not be found.
What am i missing here?
I am trying to figure out exactly what this line is for in the cmake file of this github json project,
add_library(${NLOHMANN_JSON_TARGET_NAME} INTERFACE)
add_library(${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} ALIAS ${NLOHMANN_JSON_TARGET_NAME})
Specifically with this example, what does this allow in this cmake file that otherwise would not be possible?
I see no other references to ${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} in this CMakeLists.cmake, so I am confused as to what exactly this achieves.
Edit:
The key thing that this achieves, that the comment did not make obvious to me, is that it makes the targets work with the namespaces when the project is used through add_subdirectory()
Without the alias, you can still add the library via add_subdirectory however in the target_link_libraries command you would need to omit the namespace:
project(mySuperApp)
set(mySuperApp_SRC src/main.c)
add_subdirectory(thirdparty/json)
add_executable(${PROJECT_NAME} ${mySuperApp_SRC})
target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json)
If you did that but then decided to use find_package to include the library (as opposed to add_subdirectory), you would need to change target_link_libraries to use the namespaced targets i.e.
project(mySuperApp)
set(mySuperApp_SRC src/main.c)
find_package(nlohmann_json REQUIRED)
add_executable(${PROJECT_NAME} ${mySuperApp_SRC})
target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json::nlohmann_json)
by adding the alias, the target_link_libraries using the namespaced version (i.e. nlohmann_json::nlohmann_json) will work in either case and not require a change if you later decide to switch from find_package to add_subdirectory).
It allows you to add the library with find_package OR add_subdirectory using the same target name for both:
# creates nlohmann_json::nlohmann_json
find_package(nlohmann_json REQUIRED)
if (nlohmann_json_NOT_FOUND)
# creates nlohmann_json AND nlohmann_json::nlohmann_json
add_subdirectory(thirdparty/json)
endif()
add_executable(your_target_name ${your_target_sources})
target_link_libraries(your_target_name PRIVATE nlohmann_json::nlohmann_json)
Without the alias, you would need:
# creates nlohmann_json::nlohmann_json
find_package(nlohmann_json REQUIRED)
if (NOT nlohmann_json_FOUND)
# creates only nlohmann_json
add_subdirectory(thirdparty/json)
endif()
add_executable(your_target_name ${your_target_sources})
if (nlohmann_json_FOUND)
target_link_libraries(your_target_name PRIVATE nlohmann_json::nlohmann_json)
else()
target_link_libraries(your_target_name PRIVATE nlohmann_json)
endif()
This will allow using nlohmann/json project by adding it into your super project with add_subdirectory(...)
For example simple project structure:
<root project>\
\thirdparty\json <<-- git submodule to https://github.com/nlohmann/json
\include\
\src\
CMakeLists.txt
In your project CMakeLists.txt
...
project(mySuperApp)
set(mySuperApp_SRC src/main.c)
# can under some conditions...
add_subdirectory(thirdparty/json)
add_executable(${PROJECT_NAME} ${mySuperApp_SRC})
target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json::nlohmann_json)
Using git's blame function shows that line was added in this commit: 33a2154, which has the following comment attached:
CMake convention is to use a project namespace, i.e. Foo::, for imported
targets. When multiple targets are imported from a project, this looks
like Foo::Bar1 Foo::Bar2, etc. This adds the nlohmann_json:: namespace to
the exported target names.
This also allows the generated project config files to be used from the
build directory instead of just the install directory.
I have one project that produces a library:
project (myCoolLibrary)
ADD_LIBRARY(my_cool_library SHARED ${mysources_SRC})
And another project that should be using this library:
find_package (myCoolLibrary REQUIRED)
INCLUDE_DIRECTORIES("${myCoolLibrary_INCLUDE_DIRS}" )
add_executable(myCoolExe ${my_sources_SRC} )
TARGET_LINK_LIBRARIES(myCoolExe ${myCoolLibrary_LIBRARIES} )
Is there a way that I can change the first file so that the second file works automatically? That by running CMake on the first file and then running make on the output, then running CMake on the second file, CMake is able to find the package?
An answer where I just give the address of where the first project is built to the second package is also acceptable.
Taking the code found in a blog post by #daniperez - Use CMake-enabled libraries in your CMake project (III) - I've come up with the following minimal solution:
myCoolLibrary/CMakeLists.txt
cmake_minimum_required(VERSION 3.3)
project(myCoolLibrary)
function(my_export_target _target _include_dir)
file(
WRITE "${CMAKE_CURRENT_BINARY_DIR}/${_target}Config.cmake"
"
include(\"\$\{CMAKE_CURRENT_LIST_DIR\}/${_target}Targets.cmake\")
set_property(
TARGET ${_target}
APPEND PROPERTY
INTERFACE_INCLUDE_DIRECTORIES \"${_include_dir}\"
)
"
)
export(TARGETS ${_target} FILE "${CMAKE_CURRENT_BINARY_DIR}/${_target}Targets.cmake")
# NOTE: The following call can pollute your PC's CMake package registry
# See comments/alternatives below
export(PACKAGE ${_target})
endfunction(my_export_target)
...
add_library(${PROJECT_NAME} SHARED ${mysources_SRC})
my_export_target(${PROJECT_NAME} "${CMAKE_CURRENT_SOURCE_DIR}")
myCoolExe/CMakeLists.txt
cmake_minimum_required(VERSION 3.3)
project(myCoolExe)
find_package(myCoolLibrary REQUIRED)
...
add_executable(${PROJECT_NAME} ${my_sources_SRC})
target_link_libraries(${PROJECT_NAME} myCoolLibrary)
To make it reusable I have packed everything into my_export_target(). And I'm friend of self-propagating properties like INTERFACE_INCLUDE_DIRECTORIES.
As commented by #ruslo, using export(PACKAGE ...) can pollute your package registry. So alternatively you can:
Write the target configuration files directly to some dedicated place specific for a certain toolchain
See e.g. How to install your custom CMake-Find module and 0003659: FIND_PACKAGE command improvements.
Set CMAKE_MODULE_PATH via the second project's CMake command line (injecting the search path(s) from the outside). If you are building the two projects anyway with a build script, then this is the most direct way to propagate the module search path(s).
Additional References
export()
CMake/Tutorials/Package Registry
Unable to find Eigen3 with CMake
How to instruct CMake to use the build architecture compiler
I have created a C++ static library, and in order to make it searchable easily, I create the following cmake files:
lib.cmake
# The installation prefix configured by this project.
set(_IMPORT_PREFIX "C:/------/install/win32")
# Create imported target boost
add_library(lib STATIC IMPORTED)
set_target_properties(lib PROPERTIES
INTERFACE_COMPILE_DEFINITIONS "lib_define1;lib_define2"
INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/../include"
)
# Load information for each installed configuration.
get_filename_component(_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
file(GLOB CONFIG_FILES "${_DIR}/lib-*.cmake")
foreach(f ${CONFIG_FILES})
include(${f})
endforeach()
lib-debug.cmake
# Import target "boost" for configuration "Debug"
set_property(TARGET lib APPEND PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
set_target_properties(boost PROPERTIES
IMPORTED_LINK_INTERFACE_LANGUAGES_DEBUG "CXX"
IMPORTED_LOCATION_DEBUG "${_IMPORT_PREFIX}/Debug/staticlib/lib.lib"
)
When I want to use this library in an executable, I can simply invoke it by calling find_package command:
find_package(lib REQUIRED)
if(lib_FOUND)
message("lib has been found")
else()
message("lib cannot be found")
endif(boost_FOUND)
It works and if I want to know the head file directory of the library, I will have to call it this way:
get_target_property(lib_dir lib INTERFACE_INCLUDE_DIRECTORIES)
I was just wondering whether there are other ways of obtaining the properties of an target. In this case I expect some variable like lib_INCLUDE_DIRECTORIES will exist.
No, CMake does not automatically define variables for the properties of a target (or of anything else). If you need the value of a property, you have to query it explicitly (using get_property or the specific getters like get_target_property etc.).
In your specific case, INTERFACE_INCLUDE_DIRECTORIES is a property which I would expect you would not need to query at all. The whole point of INTERFACE_* properties is to propagate usage requirements automatically; their propagation is implemented in CMake itself.