Building

Building with CMake

The distribution comes with a cmake file that should allow you to build project/make files for any platform. For details on cmake, see https://www.cmake.org. In brief, depending on your platform, use one of e.g.:

cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release
cmake -G "Visual Studio 10" -DCMAKE_BUILD_TYPE=Release
cmake -G "Xcode" -DCMAKE_BUILD_TYPE=Release

Then, build as normal for your platform. This should result in a flatc executable, essential for the next steps. Note that to use clang instead of gcc, you may need to set up your environment variables, e.g. CC=/usr/bin/clang CXX=/usr/bin/clang++ cmake -G "Unix Makefiles".

Optionally, run the flattests executable from the root flatbuffers/ directory to ensure everything is working correctly on your system. If this fails, please contact us!

Building should also produce two sample executables, flatsamplebinary and flatsampletext, see the corresponding .cpp files in the flatbuffers/samples directory.

Note that you MUST be in the root of the FlatBuffers distribution when you run ‘flattests’ or flatsampletext, or it will fail to load its files.

Make all warnings into errors

By default all Flatbuffers cmake targets are not built with the -Werror (or /WX for MSVC) flag that treats any warning as an error. This allows more flexibility for users of Flatbuffers to use newer compilers and toolsets that may add new warnings that would cause a build failure.

To enable a stricter build that does treat warnings as errors, set the FLATBUFFERS_STRICT_MODE cmake compliation flag to ON.

cmake . -DFLATBUFFERS_STRICT_MODE=ON

Our CI builds run with strict mode on, ensuring the code that is committed to the project is as portable and warning free as possible. Thus developers contributing to the project should enable strict mode locally before making a PR.

Building with VCPKG

You can download and install flatbuffers using the vcpkg dependency manager:

git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install flatbuffers

The flatbuffers port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.

Downloading binaries

You can download the binaries from the GitHub release page.

We generate SLSA3 signatures using the OpenSSF’s slsa-framework/slsa-github-generator. To verify the binaries:

1. Install the verification tool from slsa-framework/slsa-verifier#installation
2. Download the file named attestation.intoto.jsonl from the GitHub release
3. Run:

$ slsa-verifier -artifact-path <downloaded.zip> -provenance attestation.intoto.jsonl -source github.com/google/flatbuffers -tag <version>
  PASSED: Verified SLSA provenance

Building for Android

There is a flatbuffers/android directory that contains all you need to build the test executable on android (use the included build_apk.sh script, or use ndk_build / adb etc. as usual). Upon running, it will output to the log if tests succeeded or not.

You may also run an android sample from inside the flatbuffers/samples, by running the android_sample.sh script. Optionally, you may go to the flatbuffers/samples/android folder and build the sample with the build_apk.sh script or ndk_build / adb etc.

Using FlatBuffers in your own projects

For C++, there is usually no runtime to compile, as the code consists of a single header, include/flatbuffers/flatbuffers.h. You should add the include folder to your include paths. If you wish to be able to load schemas and/or parse text into binary buffers at runtime, you additionally need the other headers in include/flatbuffers. You must also compile/link src/idl_parser.cpp (and src/idl_gen_text.cpp if you also want to be able convert binary to text).

To see how to include FlatBuffers in any of our supported languages, please view the Tutorial and select your appropriate language using the radio buttons.

Using in CMake-based projects

If you want to use FlatBuffers in a project which already uses CMake, then a more robust and flexible approach is to build FlatBuffers as part of that project directly. This is done by making the FlatBuffers source code available to the main build and adding it using CMake’s add_subdirectory() command. This has the significant advantage that the same compiler and linker settings are used between FlatBuffers and the rest of your project, so issues associated with using incompatible libraries (eg debug/release), etc. are avoided. This is particularly useful on Windows.

Suppose you put FlatBuffers source code in directory ${FLATBUFFERS_SRC_DIR}. To build it as part of your project, add following code to your CMakeLists.txt file:

# Add FlatBuffers directly to our build. This defines the `flatbuffers` target.
add_subdirectory(${FLATBUFFERS_SRC_DIR}
                 ${CMAKE_CURRENT_BINARY_DIR}/flatbuffers-build
                 EXCLUDE_FROM_ALL)

# Now simply link against flatbuffers as needed to your already declared target.
# The flatbuffers target carry header search path automatically if CMake > 2.8.11.
target_link_libraries(own_project_target PRIVATE flatbuffers)

When build your project the flatbuffers library will be compiled and linked to a target as part of your project.

Override default depth limit of nested objects

To override [the depth limit of recursion](@ref flatbuffers_guide_use_cpp), add this directive:

set(FLATBUFFERS_MAX_PARSING_DEPTH 16)

to CMakeLists.txt file before add_subdirectory(${FLATBUFFERS_SRC_DIR}) line.