README.wasm

Description:
============

This file describes the compilation of libwebp using portable intrinsics /
WebAssembly (wasm) to native targets using clang and CMake.

Prerequisites:
==============

- cmake 2.8+

- clang 3.9+ for portable intrinsics support; as wasm progresses a tip of tree
  build may be necessary.

Building:
=========

 - configure the project with CMake using:

 $ mkdir -p build && \
   cd build && \
   cmake -DWEBP_BUILD_DWEBP=1 -DCMAKE_C_COMPILER=clang -DWEBP_ENABLE_WASM=1 ../

 - compile dwebp using 'make'.

 - Note this currently generates native executables only and is incompatible
   with -DWEBP_BUILD_WEBP_JS.

Cross compilation:
==================

 - arm toolchains can be obtained from:
   http://www.linaro.org/downloads/

armv7:
------
 $ gcc_arm=/opt/gcc-arm; target=arm-linux-gnueabihf

 $ cmake -DWEBP_BUILD_DWEBP=1 -DCMAKE_C_COMPILER=clang -DWEBP_ENABLE_WASM=1 \
   -DCMAKE_C_FLAGS="--target=$target --gcc-toolchain=$gcc_arm --sysroot=$gcc_arm/$target/libc" \
   -DCMAKE_PREFIX_PATH=$gcc_arm/$target/libc/usr

aarch64 / arm64:
----------------
 $ gcc_arm=/opt/gcc-aarch64; target=aarch64-linux-gnu

 $ cmake .. -DWEBP_BUILD_DWEBP=ON -DCMAKE_C_COMPILER=clang \
   -DCMAKE_C_FLAGS="--target=$target --gcc-toolchain=$gcc_arm --sysroot=$gcc_arm/$target/libc" \
   -DCMAKE_PREFIX_PATH=$gcc_arm/$target/libc/usr