I'm currently changing the build system on my project, from gnu makefiles to cmake (that generate makefiles).
My project generates several libraries (.lib), and several executables (.exe).
Currently i generate the makefiles using the following command :
cmake -G "Unix Makefiles" .. -DCMAKE_BUILD_TYPE=Debug
The generated makefiles contain an all target, as well as a target for every executable (compiled as such with the add_executable cmake directive), so i can compile a subset of the project (which saves a lot of time) : make executable_1; make executable_2 and so on.
However, there is no target for the libraries (compiled as such with the add_library cmake directive) so i cannot do make library_1 for example. I want to do this because it would save a lot of time.
I tried to add a dummy executable in the library's cmake, and link the library to this executable (which only contains a main without actually using library_1's code).
add_library(library_1 test.cpp)
add_executable(dummy_exe dummy_main.cpp)
target_link_library(dummy_exe library_1)
It does add a target for dummy_exe but does not build the library because it does not actually need to link any of the library_1's code.
This was a workaround attempt anyway, and i'd rather just call make library_1 after all. Is there any way to add a makefile target for a library using cmake ?
As answered by w-m and Fred, CMAKE indeed create a target for libraries in the Makefile.
I was trying to build the library with the cmake subproject name of the library instead of the library name.
make help was indeed of big help to find this issue, as it lists everything that can be built.
Related
I have never worked with CMake before, so please forgive any rookie mistakes. Most of the following working frame has been given to me by my project group.
The goal is to build GoogleTest into a .dll, to be used in different, indepentent parts of our project. I'm having troubles setting up CMake the right way.
The work-flow so far has been:
Clone gtest from git --> also downloads a CMake List file
Alter variables in CMakeCache.txt to have it produce a Code::Blocks project file
Compile the project file in Code::Blocks
So far, it produces a static library (.a files) that can be used in our project. I'm having troubles genereating .dll files.
Variables I have tried changing:
BUILD_SHARED_LIBS:BOOL=ON --> the files generated by Code::Blocks now have a .dll.a double extension
CMAKE_C_FLAGS and all the corresponding C++ flags where set to -DGTEST_CREATE_SHARED_LIBRARY=1 as given here
CMAKE_EXE_LINKER_FLAGS has been set to -shared to make the linker produce .dll files
I have worked my way through the GoogleTest documentation here and here but in both, building it into a .dll is merely a 2-sentence-topic.
As #Tsyvarev pointed out, the .dll files were created in a (very) different folder.
I have git cloned, built (with MSVC for both Debug and Release) and then installed wxWidgets:
cmake -B build wxWidgets
cmake --build build --config <CONFIG>
cmake --install build --prefix my_install --config <CONFIG>
with <CONFIG> = Debug and <CONFIG> = Release.
Then I used the following CMake script to link against it, as suggested by the wiki:
cmake_minimum_required(VERSION 3.16)
project(Test)
add_executable(Test WIN32 Main.cpp)
# wxWidgets
SET(wxWidgets_ROOT_DIR ${CMAKE_CURRENT_LIST_DIR}/../thirdparty/my_install)
find_package(wxWidgets COMPONENTS core base REQUIRED)
include(${wxWidgets_USE_FILE})
target_link_libraries(Test PRIVATE ${wxWidgets_LIBRARIES})
# Copy runtime DLLs to the directory of the executable.
add_custom_command(TARGET Test POST_BUILD
COMMAND ${CMAKE_COMMAND} -E echo "Runtime Dlls: $<TARGET_RUNTIME_DLLS:Test>"
)
My goal is to automatically copy the DLLs into the directory of the built executable, so that they can be found at runtime. For that I'm using the TARGET_RUNTIME_DLLS generator expression (follwing the sample code in the docs). In the code above, I only print out the expression at build time for testing purposes. The problem is that it is empty.
The approach worked for me before when installing and linking SDL, but SDL provides package configuration files which create imported targets, defining the DLL location(s) via IMPORTED_LOCATION_RELEASE or IMPORTED_LOCATION_DEBUG. For wxWidgets one is apparently supposed to use the FindwxWidgets.cmake script shipped with CMake, which sadly doesn't define the produced binaries. Maybe that's why TARGET_RUNTIME_DLLS isn't populated.
Does anyone know, either how to get TARGET_RUNTIME_DLLS filled or how to obtain the list of built wxWidgets DLLs for the current configuration (Release/Debug) post build copying?
Thanks a lot in advance!
I am dealing with a similar problem.
First sanity checks:
You have to work on windows platform otherwise this feature does not
work.
Your Cmake is 3.21 or above
Next comes fuzzy part. I think the library that you are trying to include have to be a Shared Imported library and you have to set a set_target_properties for IMPORTED_IMPLIB which is a path to a .lib file of sort (dll import library, I think it is called) So you have to make sure that it is all set in the package library that you trying to link with your executable.
If you have those dll avaiable and you just want to use them and not actually build them then you can write your own cmake script that will do just what I said above. Then you can include that cmake file in your project and then link against your app.
Note: I also work on similar issue right now and what I just said have not been working very reliably. I got some dlls to be copied and some do not.
Edit:
Cmake docs give a more detailed explanation on how this library setting should look like if you use find_package feature.
Found here: https://cmake.org/cmake/help/latest/command/add_library.html#imported-libraries
An UNKNOWN library type is typically only used in the implementation
of Find Modules. It allows the path to an imported library (often
found using the find_library() command) to be used without having to
know what type of library it is. This is especially useful on Windows
where a static library and a DLL's import library both have the same
file extension.
I have a CMake configuration file building two libraries:
a third-party library (here called ThirdPartyLib) containing a real-time OS / board support package from a supplier. It is built outside CMake using the autotools toolchain.
an extended version of the former library (here called ExtendedThirdPartyLib)
Unfortunately, some source code that I need (various tools) are not built in the ordinary build script for (1). Since I don't want to mess with the suppliers build script I want to add another library (2), building the missing files and thus extending the library from the supplier.
I want to able to do something like this in CMakeFiles.txt:
cmake_minimum_required(VERSION 3.2)
project(bsp)
include(ExternalProject)
ExternalProject_Add(
ThirdPartyLib
URL <http://some.url/bsp.tar.bz2
BUILD_COMMAND make -C ../external/ThirdPartyLib/src
)
set_target_properties(ThirdPartyLib PROPERTIES EXCLUDE_FROM_ALL TRUE)
add_library(ExtendedThirdPartyLib
${CMAKE_CURRENT_BINARY_DIR}/some/path/missing_file1.c
${CMAKE_CURRENT_BINARY_DIR}/some/path/missing_file2.c
)
add_dependencies(ExtendedThirdPartyLib ThirdPartyLib)
target_include_directories(ExtendedThirdPartyLib PUBLIC
${CMAKE_CURRENT_BINARY_DIR}/some/path/include
)
target_link_libraries(ExtendedThirdPartyLib ThirdPartyLib)
The problem here is that the path to missing_file1.c and missing_file2.c are not valid when CMake is generating the build files (they are extracted from the tarball from the supplier). CMake exits with an error output saying: "Cannot find source file".
Is there a neat way to make this work? I.e. is it possible to convince CMake that certain non-existant input files will exist when building of the library begins? Or is there any other recommended way to solve this issue?
(I have temporary made local copies of the files I need to build from the suppliers tarball, but that is of course not a good solution. If those files are changed in future versions of the suppliers package and I forget to overwrite my local copies it could be a horrible mess...
Another "solution" would be to create a small makefile outside CMake and use another ExternalProject_Add in the CMakeFiles.txt somehow. But that's not a good solution either, e.g. if compile and linker flags are modified I need to remember to change the makefile too.)
Personally, I dislike the ExternalProject_Add command, because it does way too many things for my taste, but I've digressed.
What if you do something like this, where bar is simulating your ExtendedThirdPartyLib target, since it depends on generated files
cmake_minimum_required(VERSION 3.11)
project(lol C)
set(SOURCES lol.c) # only this file exists
add_library(lol ${SOURCES})
set(FOO_FILES "foo1.c" "foo2.c")
add_custom_command(OUTPUT ${FOO_FILES}
COMMAND ${CMAKE_COMMAND} -E touch ${FOO_FILES}
WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
COMMENT "Creating ${FOO_FILES}"
VERBATIM)
add_custom_target(foo DEPENDS ${FOO_FILES})
add_library(bar ${FOO_FILES})
add_dependencies(bar foo)
target_link_libraries(lol bar)
The whole approach hinges on the fact that the method, where produced/generated files are procured, is explicitly defined via the custom command and associated custom target.
You should modify the custom command to extract the required files (e.g. could even call some external script) from the tarball (which might require downloading with curl or something similar).
How to only build a static library with clion without having an executable?
How does the CMakeLists.txt look like? (without add_executable)
Update: If I don't add executable to Clion, I have an
error, that an executable is required.
Here my CMakeLists.txt.
This is an old question. But I'll add the answer to your question as a help for other people. You need to replace your add_executable with add_library
add_library(target_name source_files)
Short answer: compile the library target and run any custom command as a placeholder to avoid the warning.
Long answer:
CLion lets you either build the whole project and run executables/configurations.
When running executables, you can choose a target to compile and the executable to run after compiling the target. For executable targets, they are usually the same thing. You compile the executable target and then run it.
It seems like this is not really designed for libraries, but there is a workaround. You usually set the target to be the library and the executable to be any executable that depends on this library. However, this is usually not very useful because if you wanted to run this executable you could just set this executable to be the target and the library would be built anyway.
So people probably want to just build the library (to check if everything is OK, etc) without compiling or running any extra executable targets. In this case, the workaround is to choose a custom executable to run after building the library, and the error message is gone.
You have nothing useful you need to run after building the library, just choose any cheap command as a placeholder. Something like "pwd" or "ls".
I have a huge project managed with CMake and this project has hundreds of components each of them having own source files and each of them linking to a list of libraries, specified with target_link_libraries(${project} some_libraries, some_other_libraries)
Now, what I am aiming for is that:
Without actually modifying any of the CMakeLists.txt I want ALL the projects's target executable to link to some specific libraries.
Is there a way of achieving this? Since this is a one time trial, I don't want to manually hunt down all the CMakeLists.txt files and modify them (yes, this is the other alternative). Just a note, I compile the entire project from command line, using cmake (no cmake gui).
This is kind of a hack, but for a C++ project, you can use CMAKE_CXX_STANDARD_LIBRARIES. For a C project, I think you would use CMAKE_C_STANDARD_LIRBARIES.
Example for C++ that links to libbar and libfoo:
cmake ... -DCMAKE_CXX_STANDARD_LIBRARIES="-lbar -lfoo"
See the documentation here:
https://cmake.org/cmake/help/v3.6/variable/CMAKE_LANG_STANDARD_LIBRARIES.html
This won't be available for older versions of CMake; it was added some time after version 3.0.
This is a dirty, dirty hack, so please only use it for testing.
You can actually overload the add_executable command by defining a function of the same name. Do this close to the top of the top-level CMakeLists.txt:
function (add_executable name)
message("Added executable: " ${name})
_add_executable(${name} ${ARGN})
target_link_libraries(${name$} your_additional_lib)
endfunction()
Note that _add_executable is an internal CMake name that may break in future CMake versions. As of now (version 3.0) it seems to work with all versions though.
You can overload add_library the same way if required.
For more fine-grained control over what is linked, instead of calling target_link_libraries you can also mess with the LINK_LIBRARIES and INTERFACE_LINK_LIBRARIES target properties directly.