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# Building TinyGo
TinyGo depends on LLVM and libclang, which are both big C++ libraries. There are
two ways these can be linked: dynamically and statically. The default is dynamic
linking because it is fast and works almost out of the box on Debian-based
systems with the right libraries installed.
This guide describes how to statically link TinyGo against LLVM and libclang so
that the binary can be easily moved between systems.
## Dependencies
LLVM and Clang are both quite light on dependencies, requiring only standard
build tools to be built. Go is of course necessary to build TinyGo itself.
* Go (1.11+)
* [dep](https://golang.github.io/dep/)
* Standard build tools (gcc/clang)
* git or subversion
* CMake
* [Ninja](https://ninja-build.org/) or make (preferably Ninja)
The rest of this guide assumes you're running Linux, but it should be equivalent
on a different system like Mac.
## Download the source
The first step is to get the source code. Place it in some directory, assuming
`$HOME/src` here, but you can pick a different one of course:
git clone -b release_70 https://github.com/llvm-mirror/llvm.git $HOME/src/llvm
git clone -b release_70 https://github.com/llvm-mirror/clang.git $HOME/src/llvm/tools/clang
go get -d github.com/tinygo-org/tinygo
cd $HOME/go/src/github.com/tinygo-org/tinygo
dep ensure -vendor-only # download dependencies
Note that Clang must be placed inside the tools subdirectory of LLVM to be
automatically built with the rest of the system.
## Build LLVM and Clang
Building LLVM is quite easy compared to some other software packages. However,
the default configuration is _not_ optimized for distribution. It is optimized
for development, meaning that binaries produce accurate error messages at the
cost of huge binaries and slow compiles.
Before configuring, you may want to set the following environment variables to
speed up the build. Most Linux distributions ship with GCC as the default
compiler, but Clang is significantly faster and uses much less memory while
producing binaries that are about as fast.
export CC=clang
export CXX=clang++
Make a build directory. LLVM requires out-of-tree builds:
mkdir $HOME/src/llvm-build
cd $HOME/src/llvm-build
Configure LLVM with CMake:
cmake -G Ninja ../llvm "-DLLVM_TARGETS_TO_BUILD=X86;ARM;AArch64" "-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=AVR;WebAssembly" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DLIBCLANG_BUILD_STATIC=ON
You can also choose a different build system than Ninja, but Ninja is fast.
There are various options you can tune here, but the options given above are
preferable for releases. Here is what they do:
* `LLVM_TARGETS_TO_BUILD` and `LLVM_EXPERIMENTAL_TARGETS_TO_BUILD`: the
targets that are natively supported by the LLVM code generators. The targets
listed here are the ones supported by TinyGo. Note that LLVM is a cross
compiler by default, unlike some other compilers.
* `CMAKE_BUILD_TYPE`: the default is Debug, which produces large inefficient
binaries that are easy to debug. We want small and fast binaries.
* `LLVM_ENABLE_ASSERTIONS`: the default is ON, which greatly slows down LLVM
and is only really useful during development. Disable them here.
* `LIBCLANG_BUILD_STATIC`: unlike LLVM, libclang is built as a shared library
by default. We want a static library for easy distribution.
Now build it:
ninja # or make, if you choose make in the previous step
This can take over an hour depending on the speed of your system.
## Build TinyGo
Now that you have a working version of LLVM, build TinyGo using it. You need to
specify the directories to the LLVM build directory and to the Clang source.
cd $HOME/go/src/github.com/tinygo-org/tinygo
make static LLVM_BUILDDIR=$HOME/src/llvm-build CLANG_SRC=$HOME/src/llvm/tools/clang
## Verify TinyGo
Try running TinyGo:
./build/tinygo help
Also, make sure the `tinygo` binary really is statically linked. Check this
using `ldd`:
ldd ./build/tinygo
The result should not contain libclang or libLLVM.
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