Cannot compile glaze example because of the CMake error

[hungptit]

I could not compile Glaze's examples using CMake's FetchContent. Everything works perfectly when I remove the in-source check from the prelude.cmake file. What am I missing?

The error message

CMake Error at _deps/glaze-src/cmake/prelude.cmake:4 (message):
  In-source builds are not supported.  Please read the BUILDING document
  before trying to build this project.  You may need to delete
  'CMakeCache.txt' and 'CMakeFiles/' first.
Call Stack (most recent call first):
  _deps/glaze-src/CMakeLists.txt:3 (include)

My glaze.cmake file

include(FetchContent)

FetchContent_Declare(
  glaze
  GIT_REPOSITORY https://github.com/stephenberry/glaze.git
  GIT_TAG v4.4.2
  GIT_SHALLOW TRUE)

set(BUILD_TESTING OFF)
set(glaze_BUILD_EXAMPLES OFF)
set(glaze_DEVELOPER_MODE OFF)
set(glaze_ENABLE_FUZZING OFF)
set(glaze_ENABLE_AVX2 ON)

FetchContent_MakeAvailable(glaze)

[stephenberry]

If you want to build the tests/examples then the recommended approach is to clone Glaze and run CMake. By default Glaze doesn't build tests when including in another project. There is a glaze_BUILD_EXAMPLES CMake option. Did you try this?

[hungptit]

Thank you for the quick response. I compile my examples outside the glaze source folder (using FetchContent). This is my CMakeLists.txt, and you can find the content of glaze.cmake in the first comment.

include(${PROJECT_SOURCE_DIR}/cmake/catch2.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/glaze.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/nanobench.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/boost.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/rapidjson.cmake)

# We cannot compile Glaze examples using clang++
set(CMAKE_CXX_COMPILER g++)

set(TEST_FILES glaze_test)
foreach(SRC_FILE ${TEST_FILES})
  add_executable(${SRC_FILE} ${SRC_FILE}.cpp)
  target_link_libraries(
    ${SRC_FILE} PRIVATE Catch2::Catch2WithMain fmt::fmt glaze::glaze nanobench
                        Boost::json utilities)
  target_include_directories(${SRC_FILE} PRIVATE ${rapidjson_SOURCE_DIR}/include
                                                 ${PROJECT_SOURCE_DIR})
  add_test(${SRC_FILE} ${SRC_FILE})
endforeach(SRC_FILE)

enable_testing()

[hungptit]

I use g++ instead of clang++ (v19.1.7) to fix compilation failures.

In file included from /home/hungptit/working/experiments/glaze/glaze_test.cpp:12:
In file included from /home/hungptit/working/experiments/_deps/glaze-src/include/glaze/json/write.hpp:24:
In file included from /home/hungptit/working/experiments/_deps/glaze-src/include/glaze/core/reflect.hpp:7:
In file included from /home/hungptit/working/experiments/_deps/glaze-src/include/glaze/core/common.hpp:17:
In file included from /home/hungptit/working/experiments/_deps/glaze-src/include/glaze/core/meta.hpp:8:
/home/hungptit/working/experiments/_deps/glaze-src/include/glaze/reflection/get_name.hpp:27:19: error: variable 'glz::detail::external<(anonymous namespace)::my_struct>' is used but not defined in this translation unit, and cannot be defined in any other translation unit because its type does not have linkage
   27 |    extern const T external;
      |                   ^
/home/hungptit/working/experiments/_deps/glaze-src/include/glaze/reflection/get_name.hpp:48:71: note: used here
   48 |    constexpr std::string_view get_name_impl = mangled_name<get_ptr<N>(external<std::remove_volatile_t<T>>)>();
      |                                                                       ^
1 error generated.
make[2]: *** [glaze/CMakeFiles/glaze_test.dir/build.make:79: glaze/CMakeFiles/glaze_test.dir/glaze_test.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:4033: glaze/CMakeFiles/glaze_test.dir/all] Error 2
make: *** [Makefile:166: all] Error 2

[stephenberry]

Clang requires the flag -stdlib=libc++ to build Glaze on Linux because of compiler bugs. But, it is tested on Clang 17, 18, and 19.