# Building

## Building with CMake

The distribution main build system is configured by
[`cmake`](https://www.cmake.org) which allows you to build the project for any
platform.

### Configuration

Use `cmake` to configure a project based on your environment and platform.

=== "Unix"

    ```sh
    cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release
    ```

To use `clang` instead of `gcc` you may need to set prepend some environment
variables e.g. `CC=/usr/bin/clang CXX=/usr/bin/clang++ cmake -G "Unix
MakeFiles"`

=== "Windows"

    ```sh
    cmake -G "Visual Studio 17 2022" -DCMAKE_BUILD_TYPE=Release
    ```

=== "MacOS"

    ```sh
    cmake -G "Xcode" -DCMAKE_BUILD_TYPE=Release
    ```

#### Strict Mode

By default, `cmake` will configure targets to **not** build with strict warnings
on (e.g. `-Werror` or `/WX`). This may cause into issues when submitting code
changes since our CI requires the code to compile in strict mode.

To enable the extra warnings, turn on strict mode with the
`FLATBUFFERS_STRICT_MODE` cmake option.

```cmake
cmake -DFLATBUFFERS_STRICT_MODE=ON
```


### Building

Once the project files are generated, build as normal for your platform.

=== "Unix"

    ```sh
    make -j
    ```

=== "Windows"

    ```sh
    msbuild.exe FlatBuffers.sln
    ```

=== "MacOS"

    ```sh
    xcodebuild -toolchain clang -configuration Release
    ```


## Building with Bazel

You can use [Bazelisk](https://github.com/bazelbuild/bazelisk) to manage your Bazel environment.
For Swift support, you also need Clang and [Swift SDK](https://download.swift.org/).

```sh
curl -sL --fail https://github.com/bazelbuild/bazelisk/releases/download/v1.25.0/bazelisk-linux-amd64 -o bazelisk && chmod +x bazelisk
sudo apt install -y clang
SWIFT_VERSION="6.0.3"
curl -L https://download.swift.org/swift-${SWIFT_VERSION}-release/debian12/swift-${SWIFT_VERSION}-RELEASE/swift-${SWIFT_VERSION}-RELEASE-debian12.tar.gz | tar xz
CC=clang PATH=$PATH:$(pwd)/swift-${SWIFT_VERSION}-RELEASE-debian12/usr/bin bazel build //...
CC=clang PATH=$PATH:$(pwd)/swift-${SWIFT_VERSION}-RELEASE-debian12/usr/bin bazel test //...
```

If you are unsure which versions to use, check our CI config at `.bazelci/presubmit.yml`.

## Building with VCPKG

You can download and install flatbuffers using the [vcpkg](https://github.com/Microsoft/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](https://github.com/Microsoft/vcpkg) on the vcpkg repository.


## 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](tutorial.md) 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 `${FLATBUFFERS_SRC_DIR}`.
To build it as part of your project, add following code to your `CMakeLists.txt` file:
```cmake
# Add FlatBuffers directly to our build. This defines the `flatbuffers` target.
add_subdirectory(${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](languages/cpp.md), 
add this directive:
```cmake
set(FLATBUFFERS_MAX_PARSING_DEPTH 16)
```
to `CMakeLists.txt` file before `add_subdirectory(${FLATBUFFERS_SRC_DIR})` line.

## Downloading binaries
You can download the binaries from the
[GitHub release page](https://github.com/google/flatbuffers/releases).

We generate [SLSA3 signatures](http://slsa.dev) using the OpenSSF's [slsa-framework/slsa-github-generator](https://github.com/slsa-framework/slsa-github-generator). To verify the binaries:
1. Install the verification tool from [slsa-framework/slsa-verifier#installation](https://github.com/slsa-framework/slsa-verifier#installation)
1. Download the file named `attestation.intoto.jsonl` from the GitHub release
1. Run:
```shell
$ slsa-verifier -artifact-path <downloaded.zip> -provenance attestation.intoto.jsonl -source github.com/google/flatbuffers -tag <version>
  PASSED: Verified SLSA provenance
```