Building BoringSSL

Build Prerequisites

  • [CMake] 1 2.8.8 or later is required.

  • Perl 5.6.1 or later is required. On Windows, [Strawberry Perl] 2 and MSYS Perl have both been reported to work. If not found by CMake, it may be configured explicitly by setting PERL_EXECUTABLE.

  • On Windows you currently must use [Ninja] 3 to build; on other platforms, it is not required, but recommended, because it makes builds faster.

  • If you need to build Ninja from source, then a recent version of [Python] 4 is required (Python 2.7.5 works).

  • On Windows only, [Yasm] 5 is required. If not found by CMake, it may be configured explicitly by setting CMAKE_ASM_NASM_COMPILER.

  • A C compiler is required. On Windows, MSVC 12 (Visual Studio 2013) or later with Platform SDK 8.1 or later are supported. Recent versions of GCC and Clang should work on non-Windows platforms, and maybe on Windows too.

  • [Go] 6 is required. If not found by CMake, the go executable may be configured explicitly by setting GO_EXECUTABLE.


Using Ninja (note the ‘N’ is capitalized in the cmake invocation):

mkdir build
cd build
cmake -GNinja ..

Using Make (does not work on Windows):

mkdir build
cd build
cmake ..

You usually don't need to run cmake again after changing CMakeLists.txt files because the build scripts will detect changes to them and rebuild themselves automatically.

Note that the default build flags in the top-level CMakeLists.txt are for debugging—optimisation isn't enabled.

If you want to cross-compile then there is an example toolchain file for 32-bit Intel in util/. Wipe out the build directory, recreate it and run cmake like this:

cmake -DCMAKE_TOOLCHAIN_FILE=../util/32-bit-toolchain.cmake -GNinja ..

If you want to build as a shared library, pass -DBUILD_SHARED_LIBS=1. On Windows, where functions need to be tagged with dllimport when coming from a shared library, define BORINGSSL_SHARED_LIBRARY in any code which #includes the BoringSSL headers.

Building for Android

It's possible to build BoringSSL with the Android NDK using CMake. This has been tested with version 10d of the NDK.

Unpack the Android NDK somewhere and export ANDROID_NDK to point to the directory. Clone into util/. Then make a build directory as above and run CMake twice like this:

cmake -DANDROID_NATIVE_API_LEVEL=android-9 \
      -DANDROID_ABI=armeabi-v7a \
      -DCMAKE_TOOLCHAIN_FILE=../util/android-cmake/android.toolchain.cmake \
      -GNinja ..

Once you've run that twice, Ninja should produce Android-compatible binaries. You can replace armeabi-v7a in the above with arm64-v8a to build aarch64 binaries.

Known Limitations on Windows

  • Versions of CMake since 3.0.2 have a bug in its Ninja generator that causes yasm to output warnings

    yasm: warning: can open only one input file, only the last file will be processed

    These warnings can be safely ignored. The cmake bug is

  • CMake can generate Visual Studio projects, but the generated project files don't have steps for assembling the assembly language source files, so they currently cannot be used to build BoringSSL.