I'd like to enhance the other solutions by providing my CMakeLists.txt
file that actually works also in terms of building dependencies.
Solution misusing CMake
cmake_minimum_required(VERSION 2.8)
add_library(lib1 test1.cpp)
add_library(lib2 test2.cpp)
include_directories(${CMAKE_CURRENT_DIR})
add_executable(mainexec main.cpp)
target_link_libraries(mainexec combinedLib) # Important to place before add_custom_target
set(LIBNAME "combinedLib.lib")
add_custom_command(
OUTPUT ${LIBNAME}
COMMAND lib.exe /OUT:${LIBNAME} $<TARGET_FILE:lib1> $<TARGET_FILE:lib2>
DEPENDS lib1 lib2
COMMENT "Combining libs..."
)
add_custom_target(combinedLib
DEPENDS ${LIBNAME}
)
Note that this solution works so far with Visual Studio but I guess it can be made multi-platform compliant. I can imagine that the following version might work for Unix-based platforms:
set(LIBNAME "libCombinedLib.a")
add_custom_command(
OUTPUT ${LIBNAME}
COMMAND ar -rcT ${LIBNAME} $<TARGET_FILE:lib1> $<TARGET_FILE:lib2>
DEPENDS lib1 lib2
COMMENT "Combining libs..."
)
Note that these solutions somehow misuse CMake as it would complain about a target of type UTILITY (instead of STATIC or SHARED) if you place the target_link_libraries
call after the add_custom_target
declaration.
CMake target-declaration-compliant solution
To make it CMake compliant, you can replace the `target_link_libraries' call by
target_link_libraries(mainexec ${LIBNAME})
add_dependencies(mainexec combinedLib)
In my case it is not entirely satisfactory because mainexec
has to know about combinedLib
although it expects all dependencies to be handled by the target_link_libraries
call.
Alternative solution with less coupling
Looking a bit further towards imported targets I eventually found a solution that solves my last problem:
cmake_minimum_required(VERSION 2.8)
add_library(lib1 test1.cpp)
add_library(lib2 test2.cpp)
include_directories(${CMAKE_CURRENT_DIR})
add_executable(mainexec main.cpp)
set(LIBNAME "combinedLib.lib")
add_custom_command(
OUTPUT ${LIBNAME}
COMMAND lib.exe /OUT:${LIBNAME} $<TARGET_FILE:lib1> $<TARGET_FILE:lib2>
DEPENDS lib1 lib2
COMMENT "Combining libs..."
)
add_custom_target(combinedLibGenerator
DEPENDS ${LIBNAME}
)
add_library(combinedLib STATIC IMPORTED)
set_property(TARGET combinedLib PROPERTY IMPORTED_LOCATION ${LIBNAME})
add_dependencies(combinedLib combinedLibGenerator)
target_link_libraries(mainexec combinedLib)
If you intend to modularize the whole add GLOBAL
after STATIC IMPORTED
to make the imported target globally visible.
Portable CMake solution
With the current CMake versions CMake provides full support for transitive dependencies and interface libraries. An interface library can then "link" against other libraries and this interface library can, in turn, be "linked" against. Why quotation marks? While this works good, this actually doesn't create a physical, combined library but rather creates a kind of an alias to the set of "sub-libs". Still this was the solution we eventually needed, which is why I wanted to add it here.
add_library(combinedLib INTERFACE)
target_link_libraries(combinedLib INTERFACE lib1 lib2)
target_link_libraries(mainexec combinedLib)
That's it!