C FFI

In addition to the HTTP and Go interfaces, the gomuks backend can be used through C function calls. The interface is mostly documented in the header file: https://github.com/gomuks/gomuks/blob/main/pkg/ffi/gomuksffi.h.

The C functions are just light wrapping to access the RPC API, so almost everything happens through the GomuksSubmitCommand function and the event callback passed to GomuksStart. There are some extra methods which can optionally be used for more advanced media features (like upload progress and download streaming).

Building

The easiest way to build the .so file is to use ./pkg/ffi/build.sh in the gomuks repo, which ends up calling go build with a bunch of flags.

If you want to cross-compile using the build script, use TARGET_GOOS and TARGET_GOARCH instead of GOOS and GOARCH respectively. Trying to set the plain variables will make go tool compile maubuild for the target instead of the host and then fail to execute it.

Additional build tags (like goolm) can be set in the GO_BUILD_TAGS environment variable. If you want a static archive (.a) instead of a dynamic library, set MAU_STATIC_BUILD=true in environment.

Building manually

You can also ignore the helper script and call go build manually. The details to note when doing that are:

• The main package is ./pkg/ffi.
• -buildmode=c-shared makes dynamic libraries and -buildmode=c-archive makes static ones. You also usually need -linkmode external -extldflags '-static' for static builds.
• -tags sqlite_fts5 is mandatory for all gomuks builds.
• Building in version info is strongly recommended. It's done by setting some variables using the -X flag. Specifically, the go.mau.fi/gomuks/version package has Commit (full git commit hash), BuildTime (RFC3339 timestamp with second precision) and Tag (git tag only if building an exact tag). Additionally, maunium.net/go/mautrix has GoModVersion which is the raw version extracted from the go.mod file.