Linking the module

[SamG101-Developer]

I am using GCC 15.2, and have built the package with modules, and see the message -- Building nlohmann.json C++ module in the console. I link it to my project in cmake using:

target_link_libraries(${PROJECT_NAME} nlohmann_json::nlohmann_json nlohmann_json_modules)

yet GCC can't find the module when I do import nlohmann.json. Is there any additional cmake things I need to do to fix the linking? Thanks.

[nlohmann]

Are you using the latest develop version?

We there have a test with the following CMake file:

cmake_minimum_required(VERSION 3.28)

project(json_test CXX)

set(NLOHMANN_JSON_BUILD_MODULES ON CACHE BOOL "Enable nlohmann.json module support")

add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/../.. ${CMAKE_CURRENT_BINARY_DIR}/tests)

add_executable(json_test main.cpp)
target_link_libraries(json_test 
    PRIVATE 
        nlohmann_json_modules
)

target_compile_definitions(json_test 
    PRIVATE NLOHMANN_JSON_BUILD_MODULES
)

target_compile_features(json_test PUBLIC cxx_std_20)

That works with GCC.

[SamG101-Developer]

I am on the latest edition of develop. I built with these commands:

• cmake -Bbuild -GNinja -DNLOHMANN_JSON_BUILD_MODULES=ON
• cmake --build build
• sudo cmake --install build

I have a target_link_libraries like:

target_link_libraries(
        ${PROJECT_NAME}_lib PRIVATE OpenSSL::SSL OpenSSL::Crypto spdlog::spdlog Boost::serialization
        nlohmann_json_modules CLI11::CLI11 ipaddress::ipaddress ipaddress::ipaddress-module ${DEPS_LIBRARIES})

Also just tried target_compile_definitions too but no effect.

[nlohmann]

Strange. For reference, here is the full test code: https://github.com/nlohmann/json/blob/develop/cmake/ci.cmake#L662-L672