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Diffstat (limited to 'third_party/abseil-cpp/CMake/README.md')
| -rw-r--r-- | third_party/abseil-cpp/CMake/README.md | 96 |
1 files changed, 90 insertions, 6 deletions
diff --git a/third_party/abseil-cpp/CMake/README.md b/third_party/abseil-cpp/CMake/README.md index 04d5df3ab0..f8b27e63f6 100644 --- a/third_party/abseil-cpp/CMake/README.md +++ b/third_party/abseil-cpp/CMake/README.md @@ -34,15 +34,16 @@ to include Abseil directly in your CMake project. 4. Add the **absl::** target you wish to use to the [`target_link_libraries()`](https://cmake.org/cmake/help/latest/command/target_link_libraries.html) section of your executable or of your library.<br> -Here is a short CMakeLists.txt example of a project file using Abseil. +Here is a short CMakeLists.txt example of an application project using Abseil. ```cmake -cmake_minimum_required(VERSION 3.5) -project(my_project) +cmake_minimum_required(VERSION 3.8.2) +project(my_app_project) # Pick the C++ standard to compile with. # Abseil currently supports C++11, C++14, and C++17. set(CMAKE_CXX_STANDARD 11) +set(CMAKE_CXX_STANDARD_REQUIRED ON) add_subdirectory(abseil-cpp) @@ -50,9 +51,47 @@ add_executable(my_exe source.cpp) target_link_libraries(my_exe absl::base absl::synchronization absl::strings) ``` +Note that if you are developing a library designed for use by other clients, you +should instead leave `CMAKE_CXX_STANDARD` unset (or only set if being built as +the current top-level CMake project) and configure the minimum required C++ +standard at the target level. If you require a later minimum C++ standard than +Abseil does, it's a good idea to also enforce that `CMAKE_CXX_STANDARD` (which +will control Abseil library targets) is set to at least that minimum. For +example: + +```cmake +cmake_minimum_required(VERSION 3.8.2) +project(my_lib_project) + +# Leave C++ standard up to the root application, so set it only if this is the +# current top-level CMake project. +if(CMAKE_SOURCE_DIR STREQUAL my_lib_project_SOURCE_DIR) + set(CMAKE_CXX_STANDARD 17) + set(CMAKE_CXX_STANDARD_REQUIRED ON) +endif() + +add_subdirectory(abseil-cpp) + +add_library(my_lib source.cpp) +target_link_libraries(my_lib absl::base absl::synchronization absl::strings) + +# Enforce that my_lib requires C++17. Important to document for clients that they +# must set CMAKE_CXX_STANDARD to 17 or higher for proper Abseil ABI compatibility +# (since otherwise, Abseil library targets could be compiled with a lower C++ +# standard than my_lib). +target_compile_features(my_lib PUBLIC cxx_std_17) +if(CMAKE_CXX_STANDARD LESS 17) + message(FATAL_ERROR + "my_lib_project requires CMAKE_CXX_STANDARD >= 17 (got: ${CMAKE_CXX_STANDARD})") +endif() +``` + +Then the top-level application project that uses your library is responsible for +setting a consistent `CMAKE_CXX_STANDARD` that is sufficiently high. + ### Running Abseil Tests with CMake -Use the `-DABSL_RUN_TESTS=ON` flag to run Abseil tests. Note that if the `-DBUILD_TESTING=OFF` flag is passed then Abseil tests will not be run. +Use the `-DBUILD_TESTING=ON` flag to run Abseil tests. You will need to provide Abseil with a Googletest dependency. There are two options for how to do this: @@ -70,7 +109,7 @@ For example, to run just the Abseil tests, you could use this script: cd path/to/abseil-cpp mkdir build cd build -cmake -DABSL_USE_GOOGLETEST_HEAD=ON -DABSL_RUN_TESTS=ON .. +cmake -DBUILD_TESTING=ON -DABSL_USE_GOOGLETEST_HEAD=ON .. make -j ctest ``` @@ -93,9 +132,54 @@ absl::flags absl::memory absl::meta absl::numeric -absl::random +absl::random_random absl::strings absl::synchronization absl::time absl::utility ``` + +## Traditional CMake Set-Up + +For larger projects, it may make sense to use the traditional CMake set-up where you build and install projects separately. + +First, you'd need to build and install Google Test: +``` +cmake -S /source/googletest -B /build/googletest -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/installation/dir -DBUILD_GMOCK=ON +cmake --build /build/googletest --target install +``` + +Then you need to configure and build Abseil. Make sure you enable `ABSL_USE_EXTERNAL_GOOGLETEST` and `ABSL_FIND_GOOGLETEST`. You also need to enable `ABSL_ENABLE_INSTALL` so that you can install Abseil itself. +``` +cmake -S /source/abseil-cpp -B /build/abseil-cpp -DCMAKE_PREFIX_PATH=/installation/dir -DCMAKE_INSTALL_PREFIX=/installation/dir -DABSL_ENABLE_INSTALL=ON -DABSL_USE_EXTERNAL_GOOGLETEST=ON -DABSL_FIND_GOOGLETEST=ON +cmake --build /temporary/build/abseil-cpp +``` + +(`CMAKE_PREFIX_PATH` is where you already have Google Test installed; `CMAKE_INSTALL_PREFIX` is where you want to have Abseil installed; they can be different.) + +Run the tests: +``` +ctest --test-dir /temporary/build/abseil-cpp +``` + +And finally install: +``` +cmake --build /temporary/build/abseil-cpp --target install +``` + +# CMake Option Synposis + +## Enable Standard CMake Installation + +`-DABSL_ENABLE_INSTALL=ON` + +## Google Test Options + +`-DBUILD_TESTING=ON` must be set to enable testing + +- Have Abseil download and build Google Test for you: `-DABSL_USE_EXTERNAL_GOOGLETEST=OFF` (default) + - Download and build latest Google Test: `-DABSL_USE_GOOGLETEST_HEAD=ON` + - Download specific Google Test version (ZIP archive): `-DABSL_GOOGLETEST_DOWNLOAD_URL=https://.../version.zip` + - Use Google Test from specific local directory: `-DABSL_LOCAL_GOOGLETEST_DIR=/path/to/googletest` +- Use Google Test included elsewhere in your project: `-DABSL_USE_EXTERNAL_GOOGLETEST=ON` +- Use standard CMake `find_package(CTest)` to find installed Google Test: `-DABSL_USE_EXTERNAL_GOOGLETEST=ON -DABSL_FIND_GOOGLETEST=ON` |