Rust + Go(lang)

TL;DR: Call Rust code from Go using FFI

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This repository shows how, by combining cgo and Rust's FFI capabilities, we can call Rust code from Go.

To ways of achieving this are presented in this repository: with a dynamic library, and with a static library.

Running the example code

Run make run-all to see Rust + Go in action, building and running two binaries, one where the Rust code is compiled as a dynamic (sometimes also referred to as a 'shared') library, and one where it is compiled as a static library.

You should see the following output:

$ make run-all
   Compiling libc v0.2.132
   Compiling hello v0.1.0 (/home/user/rust-plus-golang/lib/hello)
    Finished release [optimized] target(s) in 0.1s
Hello world!
(this is code from the dynamic library)
    Finished release [optimized] target(s) in 0.00s
Hello world!
(this is code from the static library)

You will also find the binaries ./main_dynamic and ./main_static in your current working directory.

How it works

The Rust code is packaged up into a dynamic library and a static library, and the two Go binaries then call these using cgo.

You can do this for your own project

Andrew Oppenlander's article on creating a Rust dynamic library is a great introduction to this topic.

1. Begin by creating a lib directory, where you will keep your Rust libraries.
2. Then, create a C header file for your library. See the example hello.h.
3. All that is left to do is to add some cgo-specific comments to your Go code. These comments tell cgo where to find the library and its headers.

Dynamic library setup

The following cgo comments are required to use a dynamic library:

/*
#cgo LDFLAGS: -L./lib -lhello
#include "./lib/hello.h"
*/
import "C"

You must also pass the -ldflags option to go build (see the build-dynamic target in the Makefile).

See main_dynamic.go

Static library setup

For a static library, an additional -ldl LDFLAGS flag is sometimes necessary. This flag will link the dl library.

/*
#cgo LDFLAGS: ./lib/libhello.a -ldl
#include "./lib/hello.h"
*/
import "C"

There should not be a newline between */ and import "C".

See the build-static target in the Makefile and main_dynamic.go.

See also

• rustgo: Calling Rust from Go with near-zero overhead
• Hooking Go from Rust