CODEWITHSUNDEEP
cmake
Tom de Geus
Tom de Geus

Reputation: 5965

Cannot specify compile options for imported target "..."

I want to provide the users of my library with two targets: one that specifies the include path etc., and one that carries useful extra compile options. However, for the extra target some of my users are getting the error 

Cannot specify compile options for imported target "myproject::extra"

so it seems on older CMake versions.

I tested with CMake 3.9.2. The test project, including CI is on GitHub, with failing build here.

(How) can my approach be rendered robust for all CMake versions?

The project's main CMakeLists.txt:

cmake_minimum_required(VERSION 3.0)
project(myproject)
add_library(myproject INTERFACE)
set(MYPROJECT_VERSION "1.0.0")

target_include_directories(myproject INTERFACE
    $<INSTALL_INTERFACE:include>
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)

include(CMakePackageConfigHelpers)
include(GNUInstallDirs)

install(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/include/" DESTINATION include)
install(TARGETS myproject EXPORT myproject-targets)
install(EXPORT myproject-targets FILE myprojectTargets.cmake DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/myproject")
write_basic_package_version_file("${CMAKE_CURRENT_BINARY_DIR}/myprojectConfigVersion.cmake" VERSION ${MYPROJECT_VERSION} COMPATIBILITY AnyNewerVersion)
install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/myprojectConfig.cmake" "${CMAKE_CURRENT_BINARY_DIR}/myprojectConfigVersion.cmake" DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/myproject")

The project's myprojectConfig.cmake:

include(CMakeFindDependencyMacro)

if(NOT TARGET myproject)
    include("${CMAKE_CURRENT_LIST_DIR}/myprojectTargets.cmake")
endif()

if(NOT TARGET myproject::extra)
    add_library(myproject::extra INTERFACE IMPORTED)
    if(MSVC)
        target_compile_options(myproject::extra INTERFACE /W4)
    else()
        target_compile_options(myproject::extra INTERFACE -Wall)
    endif()
endif()

The user's project CMakeLists.txt could then look as follows:

cmake_minimum_required(VERSION 3.0)
project(myexec)
find_package(myproject REQUIRED)
add_executable(myexec main.cpp)
target_link_libraries(myexec PRIVATE myproject myproject::extra)

Upvotes: 2

Views: 4201

Answers (1)

Tsyvarev
Tsyvarev

Reputation: 65928

List of functions applicable for IMPORTED and INTERFACE targets changes as CMake evolves.

Most of such functions affects only on specific target properties. So, instead of calling a function, you may set the property directly. This will work in any CMake version:

# Works only in new CMake versions
target_compile_options(myproject::extra INTERFACE /W4)
# Equivalent which works in any CMake version
set_property(TARGET myproject::extra PROPERTY INTERFACE_COMPILE_OPTIONS /W4)

Upvotes: 2

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