Abseil CMake Build Instructions
Abseil comes with a CMake build script (CMakeLists.txt) that can be used on a wide range of platforms ("C" stands for cross-platform.). If you don't have CMake installed already, you can download it for free from https://www.cmake.org/.
CMake works by generating native makefiles or build projects that can be used in the compiler environment of your choice.
For API/ABI compatibility reasons, we strongly recommend building Abseil in a subdirectory of your project or as an embedded dependency.
Incorporating Abseil Into a CMake Project
The recommendations below are similar to those for using CMake within the googletest framework (https://github.com/google/googletest/blob/master/googletest/README.md#incorporating-into-an-existing-cmake-project)
Step-by-Step Instructions
-
If you want to build the Abseil tests, integrate the Abseil dependency Google Test into your CMake project. To disable Abseil tests, you have to pass
-DBUILD_TESTING=OFFwhen configuring your project with CMake. -
Download Abseil and copy it into a subdirectory in your CMake project or add Abseil as a git submodule in your CMake project.
-
You can then use the CMake command
add_subdirectory()to include Abseil directly in your CMake project. -
Add the absl:: target you wish to use to the
target_link_libraries()section of your executable or of your library. Here is a short CMakeLists.txt example of an application project using Abseil.
```cmake 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)
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 -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:
- Use
-DABSL_USE_GOOGLETEST_HEAD. This will automatically download the latest Googletest source into the build directory at configure time. Googletest will then be compiled directly alongside Abseil's tests. - Manually integrate Googletest with your build. See https://github.com/google/googletest/blob/master/googletest/README.md#using-cmake for more information on using Googletest in a CMake project.
For example, to run just the Abseil tests, you could use this script:
cd path/to/abseil-cpp
mkdir build
cd build
cmake -DBUILD_TESTING=ON -DABSL_USE_GOOGLETEST_HEAD=ON ..
make -j
ctest
Currently, we only run our tests with CMake in a Linux environment, but we are working on the rest of our supported platforms. See https://github.com/abseil/abseil-cpp/projects/1 and https://github.com/abseil/abseil-cpp/issues/109 for more information.
Available Abseil CMake Public Targets
Here's a non-exhaustive list of Abseil CMake public targets:
cmake
absl::algorithm
absl::base
absl::debugging
absl::flat_hash_map
absl::flags
absl::memory
absl::meta
absl::numeric
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