I have a CMake project with two subprojects, a library and an application using it. The application needs several build configurations (custom values in CMAKE_CONFIGURATION_TYPES). However for the library there is no difference between those configurations. Is it possible to modify the configuration set in subproject and still use it's output in the parent or sibling project?
Hmm, did you tried something like this in library project:
if(CMAKE_BUILD_TYPE STREQUAL "Your_custom_config")
set(CMAKE_BUILD_TYPE "Release")
endif()
Related
I have a top-level CMakeLists.txt which includes another third party project from a subdirectory, like
add_subdirectory(ext/third_party/cmake)
third_party contains a library target which I want to build, but I want to modify some properties and want to avoid to modify the original CMake file. I do not want to link some of my own targets to that library, I'd rather want that third party library to be build with some modified properties and then put it into a custom output directory. So I do
set_target_properties(libthird_party PROPERTIES
# some properties that successfully get applied here
LIBRARY_OUTPUT_DIRECTORY "/my/output/dir")
I can see that other properties are successfully applied and the build is modified to my needs correctly, but the generated output library is not put into the directory I set. What could be the reason for that?
If this is a totally wrong or bad approach please also feel free to propose a better approach for my goal.
Figured it out myself with help from the comments. I was trying to modify a static library target, which is not affected by LIBRARY_OUTPUT_DIRECTORY (which only applies to dynamic libraries) but which needs the setting ARCHIVE_OUTPUT_DIRECTORY. So the corrected call is
set_target_properties(libthird_party PROPERTIES
# some properties that successfully get applied here
ARCHIVE_OUTPUT_DIRECTORY "/my/output/dir")
You have to deal with [LIBRARY, ARCHIVE, EXECUTABLE] x [Single, Multi]config generator x [Unix, Windows]way.
note: On Windows everything (.dll, .exe) is on the same directory while on Unix you generally have a bin and a lib directories.
include(GNUInstallDirs)
# Single config (e.g. makefile, ninja)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})
if(UNIX)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
else()
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})
endif()
# For multi-config build system (e.g. xcode, msvc, ninja-multiconfig)
foreach(OUTPUTCONFIG IN LISTS CMAKE_CONFIGURATION_TYPES)
string(TOUPPER ${OUTPUTCONFIG} OUTPUTCONFIG)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY_${OUTPUTCONFIG}
${CMAKE_BINARY_DIR}/${OUTPUTCONFIG}/${CMAKE_INSTALL_BINDIR})
if(UNIX)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY_${OUTPUTCONFIG}
${CMAKE_BINARY_DIR}/${OUTPUTCONFIG}/${CMAKE_INSTALL_LIBDIR})
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY_${OUTPUTCONFIG}
${CMAKE_BINARY_DIR}/${OUTPUTCONFIG}/${CMAKE_INSTALL_LIBDIR})
else()
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY_${OUTPUTCONFIG}
${CMAKE_BINARY_DIR}/${OUTPUTCONFIG}/${CMAKE_INSTALL_BINDIR})
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY_${OUTPUTCONFIG}
${CMAKE_BINARY_DIR}/${OUTPUTCONFIG}/${CMAKE_INSTALL_BINDIR})
endif()
endforeach()
In CMake there are imported modules that are used to simply add external modules to local targets. For example if we want to use boost::filesystem library in our project we could have a CMakeLists.txt like this:
project(foo CXX)
find_packge(Boost REQUIRED COMPONENTS filesystem)
add_executable(foo main.cpp)
target_link_libraries(foo Boost::filesystem)
With above configuration CMake will add proper compiler options and include directories among required libraries to building process of the foo.
Now we have to build a library instead of an executable and we don't want to link boost::filesystem libraries to our library. We want only compiler options and include directories to be added to our target. Could we use imported modules concepts here? I mean that if we could use Boost::filesystem syntax for adding those options to our target?
project(foo CXX)
find_packge(Boost REQUIRED COMPONENTS filesystem)
add_library(foo STATIC foo.cpp)
# what should be wrote here to only add headers and configs to foo not the libs?
Turning my comments into an answer
add_library(STATIC) won't link the target_link_libraries() dependencies into itself.
In short, if two static libraries would include e.g. Boost::filesystem and then you link both of those libraries into an executable (where the external symbols get actually resolved) you would get duplicate symbol errors.
So CMake by default, does not add linker options like --whole-archive for gcc or LinkLibraryDependencies for VC.
target_link_libraries(foo Boost::filesystem) should work, it just describes the dependency resolved later when building a executable or shared library.
References
ld linker question: the --whole-archive option
CMake issue #9732: Cmake does not disable Link Libray Dependencies in the project settings
I have several projects consisting of a few libraries, each living in its own subdirectory, knitted together by the topmost CMakeLists.txt file. I am in the habit of using project(<DIRNAME>) at the top of each CMakeLists.txt file and I try to structure the subprojects in such a way that they could be compiled separately from the top project. However, while this might make sense for standalone, core libraries, it cannot work for the libraries that depend on them because I need to do stuff like
target_link_libraries(gui core)
And core will nor be defined if I am trying to compile gui as a standalone project.
Is it wrong to use project() in this context, or am I missing something?
A Matter of Taste
This is in my opinion mainly a matter of taste. I don't think multiple project() commands itself are a problem, its more that projects I have seen using this approach tend to repeat itself in other parts and sometimes are running into problems with global cached variables.
Depending Libraries
The more relevant fact is, that the depending libraries will also add an include dependencies.
For standalone static library targets - not executable or shared library targets who really link the library - the simple target_link_libraries() command could be ignored with something like:
if (TARGET core)
target_link_libraries(gui core)
endif()
But the header files include dependency remains.
Standalone Projects in CMake
For me a (sub-)project to be really standalone needs not only the project() command, but it should also have a export(TARGETS ...) command. Then you could e.g. use find_package() commands to resolve any open dependencies with something like:
if (NOT TARGET core)
find_package(core REQUIRED)
endif()
target_link_libraries(gui core)
References
Making cmake library accessible by other cmake packages automatically
CMake share library with multiple executables
I have the following cmake setup:
colorizer_root
|
|-------colorizer_lib
|-------colorizer_template_project
The colorizer_root contains the top level CMakeLists.txt which is invoked when running cmake:
colorizer_root CMakeLists.txt
project(colorizer_root)
cmake_minimum_required(VERSION 2.8)
set(CMAKE_BUILD_TYPE Debug)
add_subdirectory(colorizer_lib)
add_subdirectory(colorizer_template_project)
As you can see it contains 2 subdirectories each a project on its own. Basically what the colorizer_lib does is create a shared library named libcolorize.so (no executables here!), which then is to be used by the other project colorizer_template_project (the executable is created in this project). Here are the two CMakeLists.txt files for their respective projects:
colorizer_lib CMakeLists.txt
project(colorizer_lib)
cmake_minimum_required(VERSION 2.8)
set(CMAKE_CXX_FLAGS "--std=gnu++11 ${CMAKE_CXX_FLAGS}")
include_directories(. INCLUDES)
add_library(colorizer SHARED colorizer.cpp)
colorizer_template_project CMakeLists.txt
project(colorizer_template_project)
cmake_minimum_required(VERSION 2.8)
find_library(COLORIZER_LIB colorizer
PATHS ${CMAKE_BINARY_DIR}/colorizer_lib
)
aux_source_directory(. SRC_LIST)
add_executable(${PROJECT_NAME} ${SRC_LIST})
target_link_libraries(${PROJECT_NAME} ${COLORIZER_LIB})
I'm having trouble figuring out how the whole lookup thing works. The problem here is that when I run the top level CMakeLists.txt it goes through both (obviously) but during processing the colorizer_template_project it breaks with a complaint:
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
COLORIZER_LIB
linked by target "colorizer_template_project" in directory /home/USER/Programming/C_Cpp/colorizer/colorizer_template_project
This is an expected behaviour since libcolorizer.so cannot be present at the time of running cmake because it is created after make has been invoked.
How do I tell cmake to first process the first project (including the build step!) and then go to the next one? I know that this works if I add an executable to the project that creates the library and then directly link it to the binary but in this case I want separate projects for the library and the executable that is using it.
PS: I haven't given any details about the sources because they are not important here. It is - I believe - a general question, which is not specific to whether I'm using C, C++ or something similar.
project command doesn't make subprojects independent, so colorizer target is actually accessible for colorizer_template_project, and you can directly link with it:
add_executable(${PROJECT_NAME} ${SRC_LIST})
target_link_libraries(${PROJECT_NAME} colorizer)
Lets say I have a project with two independent subprojects. If I understood cmake correctly, the idea would be to have one root CMakeLists.txt defining a project(...) and then using add_subdirectory(...) to include the subprojects. Each subproject would have its own CMakeLists.txt defining its own project. This way projects can be build either together (using the root cmake file) or individually (using the subprojects cmake file).
I now would like to change the CMAKE_CONFIGURATION_TYPES. Should I do this in the root CMakeLists.txt or in each subproject, or both?
Changing it in the root would mean that building a subproject individually would offer the wrong configuration types; the other options would duplicate the cmake code. I think I'm missing something here.
Factorize out the code that sets up configuration-dependent settings. Create a file, say, SetUpConfigurations.cmake with this content:
if(NOT SET_UP_CONFIGURATIONS_DONE)
set(SET_UP_CONFIGURATIONS_DONE TRUE)
# No reason to set CMAKE_CONFIGURATION_TYPES if it's not a multiconfig generator
# Also no reason mess with CMAKE_BUILD_TYPE if it's a multiconfig generator.
get_property(isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
if(isMultiConfig)
set(CMAKE_CONFIGURATION_TYPES "Debug;Release;Profile" CACHE STRING "" FORCE)
else()
if(NOT CMAKE_BUILD_TYPE)
message("Defaulting to release build.")
set(CMAKE_BUILD_TYPE Release CACHE STRING "" FORCE)
endif()
set_property(CACHE CMAKE_BUILD_TYPE PROPERTY HELPSTRING "Choose the type of build")
# set the valid options for cmake-gui drop-down list
set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug;Release;Profile")
endif()
# now set up the Profile configuration
set(CMAKE_C_FLAGS_PROFILE "...")
set(CMAKE_CXX_FLAGS_PROFILE "...")
set(CMAKE_EXE_LINKER_FLAGS_PROFILE "...")
endif()
Then include(..) this file at the beginning of the CMakeLists.txt's.
You have two choices about where to put SetUpConfigurations.cmake, it depends on how you organize your projects, repositories:
The quick'n'dirty way: Copy and commit this script into each project that needs it. Its location will be fixed, relative to the CMakeLists.txt of the project. So you can include it, for example, with include(${CMAKE_CURRENT_SOURCE_DIR}/<...>/SetUpConfigurations.cmake)
The disciplined way: Maintain a repository with your custom CMake scripts, like this one. Each time you generate a project with the cmake command, you pass the path to this repository in the CMAKE_MODULE_PATH variable:
cmake -DCMAKE_MODULE_PATH=<dir-of-cmake-script-repo> ...
In this case include the script with include(SetUpConfigurations) (no .cmake extension).
A note about what a multiconfig generator is:
Xcode and Visual Studio are multiconfig generators. They respect the value of CMAKE_CONFIGURATION_TYPES but CMAKE_BUILD_TYPE has no effect since no concrete configuration is defined when the CMakeLists.txt is processed. It will be selected on the IDE's user interface later.
On the other hand, the makefile-style generators are not interested in CMAKE_CONFIGURATION_TYPES. CMAKE_BUILD_TYPE defines the configuration. It is a concrete value when the CMakeLists.txt file is processed but still: never make any decisions based on the value of CMAKE_BUILD_TYPE:
if(CMAKE_BUILD_TYPE STREQUAL "Release") # WRONG!
....
endif()
You project won't work as intended in multiconfig generators.
When use add_subdirectory into subproject dir, you propagate almost all variables into that subproject, which contradicts to "subproject independency".
Instead, it is better to build and install subproject using nested cmake call inside execute_process(). If you want to make some subproject's definitions available for top-level project, you need to "export" this definitions when subproject is installed. This question/answer post describes, how to do that.