DistClang is the Clang compiler extension with a client-server infrastructure. It features the distributed cross-platform compilation and the intermediate result caching.

The project consists of 2 executables and a couple of configuration files.

clang is a client part and should reside on the machine where the compilation is invoked. It should replace the invocation of the original compiler.

clangd is a server that has 2 different roles: emitter and absorber.

How to build

First of all do clone with an argument --recurse-submodules and then configure the project:

./build/configure

To build You have to use a recent Clang compiler with C++14 support.

For debugging and local usage

ninja -C out/Debug.gn All
cd out/Debug.gn
ln -s clang clang++

The resulting files clang, clang++ and clangd are located in the out/Debug.gn folder.

Linux DEB and RPM packages

ninja -C out/Release.gn rpm_package deb_package

The resulting packages are:

out/Release.gn/dist-clang_<version>_amd64.deb
out/Release.gn/rpmbuild/RPMS/x86_64/dist-clang-<version>-1.x86_64.rpm

Don't use locally the clang and clangd from the out/Release.gn folder since they are hardcoded to use libraries from /usr/lib/dist-clang folder.

Mac OS X package

ninja -C out/Release.gn pkg_package

The resulting package is out/Release.gn/dist-clang-<version>.pkg

How to configure the emitter

TODO!

How to configure the absorber

TODO!

How to run local compilation

The basics is to make use of dist-clang's clang and clang++ as the compilers. Doing

export CC=/usr/bin/dist-clang/clang CXX=/usr/bin/dist-clang/clang++

possibly should work almost always.

To work properly the dist-clang should know about the real compiler's path and compiler's version.

Use local config file

One way to provide information about a real compiler is to put config file somewhere on the path to the folder where the build is performed. File must be named .distclang and should contain something like this:

path: "third_party/llvm-build/Release+Asserts/bin/clang"
version: "clang version 3.7.0 (trunk 231690)"

Use environment variables

Another way - is to set some env. vars:

export DC_CLANG_PATH="/usr/bin/clang"
export DC_CLANG_VERSION="clang version 3.7.0 (trunk 231690)"

Rely on auto-detect

The last resort is to use dist-clang's auto-detect feature: it tries to find the next clang in the path, that differs from the current binary, i.e. /usr/bin/dist-clang/clang. It's a not recommended and error-prone way, since internally paths are compared as a raw strings - without link resolution, etc.

In any way, if the clang path is provided without version, then the version is carved out of the real clang's output.