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Cmake config improvements #1271

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Merged
merged 6 commits into from
May 5, 2021
Merged

Cmake config improvements #1271

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0402378
- exported targets go to separate generated file and package config …
sergeyrachev Feb 27, 2021
6a076e3
- declare namespaced export target to simplify the library usage
sergeyrachev Feb 27, 2021
cfb9120
- empty line at end of file
sergeyrachev Feb 27, 2021
37ce902
- narrowed lines to be aligned with overall file line width
sergeyrachev Mar 6, 2021
6f6613a
- workaround for CMake < 3.18 ALIAS target limitation to not point to…
sergeyrachev Apr 2, 2021
816ef22
- isolated namespace targets into separate file
sergeyrachev Apr 14, 2021
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8 changes: 6 additions & 2 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -177,11 +177,15 @@ if(JSONCPP_WITH_CMAKE_PACKAGE)
include(CMakePackageConfigHelpers)
install(EXPORT jsoncpp
DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/jsoncpp
FILE jsoncppConfig.cmake)
FILE jsoncpp-targets.cmake)
configure_package_config_file(jsoncppConfig.cmake.in ${CMAKE_CURRENT_BINARY_DIR}/jsoncppConfig.cmake
INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/jsoncpp)

write_basic_package_version_file("${CMAKE_CURRENT_BINARY_DIR}/jsoncppConfigVersion.cmake"
VERSION ${PROJECT_VERSION}
COMPATIBILITY SameMajorVersion)
install(FILES ${CMAKE_CURRENT_BINARY_DIR}/jsoncppConfigVersion.cmake
install(FILES
${CMAKE_CURRENT_BINARY_DIR}/jsoncppConfigVersion.cmake ${CMAKE_CURRENT_BINARY_DIR}/jsoncppConfig.cmake
DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/jsoncpp)
endif()

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18 changes: 18 additions & 0 deletions jsoncppConfig.cmake.in
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
cmake_policy(PUSH)
cmake_policy(VERSION 3.0)

@PACKAGE_INIT@

include ( "${CMAKE_CURRENT_LIST_DIR}/jsoncpp-targets.cmake" )

if(TARGET jsoncpp_static)
add_library(JsonCpp::JsonCpp INTERFACE IMPORTED )
set_target_properties(JsonCpp::JsonCpp PROPERTIES INTERFACE_LINK_LIBRARIES "jsoncpp_static")
elseif(TARGET jsoncpp_lib)
add_library(JsonCpp::JsonCpp INTERFACE IMPORTED )
set_target_properties(JsonCpp::JsonCpp PROPERTIES INTERFACE_LINK_LIBRARIES "jsoncpp_lib")
endif()
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I would put this logic in a file jsoncpp-namespaced-targets.cmake exported with install(EXPORT ...).
Moreover, for consistency with add_subdirectory(), JsonCpp::JsonCpp ALIAS target should be added in CMakeLists.

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I would put this logic in a file jsoncpp-namespaced-targets.cmake exported with install(EXPORT ...).

You mean such that lines 6-7 above read like this?

include ( "${CMAKE_CURRENT_LIST_DIR}/jsoncpp-targets.cmake" )
include ( "${CMAKE_CURRENT_LIST_DIR}/jsoncpp-namespaced-targets.cmake" )

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That's it 😃

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Right. And about the ALIAS target, where would you do that?

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@SpaceIm SpaceIm Apr 14, 2021 •
edited
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In /src/lib_json/CMakeLists.txt close to add_library() calls. Unfortunately, it will probably requires some ugly branching because currently jsoncpp can build both shared & static, or shared only, or static only.

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I would be glad to add ALIAS to CMakeLists to use the namespaced target in build tree also.
What is the usecase of having both static and shared build at same time? CMake allows to specify the library type during generation with -DBUILD_SHARED_LIBS=Off/On although it relies on CMakeLists.txt to not specify types explicitly.

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@spacelm: Could we imagine fixing the include part of your comment in this PR, and leaving the ALIAS part for another PR? So that there could be a discussion about @sergeyrachev's point with which I agree: why not relying on BUILD_SHARED_LIBS instead? That makes it simpler IMO, and if you want both, you can run the build twice 🤔.

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@SpaceIm SpaceIm Apr 14, 2021 •
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No problem for me to add ALIAS target in another PR, it would be an improvement.

Then, you can introduce a new breaking change in jsoncpp by removing again the ability to build both static & shared (AFAIK, it was removed for 1.9.0, then introduced again in 1.9.4...). Since I'm against build of both static & shared, I would be happy, but I'm not the maintainer.


check_required_components(JsonCpp)

cmake_policy(POP)