description

golib is a library exposing Go's channels and goroutines to plain C and to any other language able to use C libraries.

There are three catches:

• your main() function needs to call golib_main() which will not return control to it. You should put the actual main code in another function with the assembler name of 'main.main' (see examples).
• you need to use write barriers when assigning pointers
• we use gccgo (from upstream GCC) instead of the main Go toolchain, for technical reasons, so the channel/goroutine performance is lower and the memory usage is higher.

requirements

• GCC with Go support (tested with GCC 7.3.0, 8.2.0).

inspiration

• this Stack Overflow response
• uWSGI's gccgo plugin
• GCC's libgo

discussion

The main problem with libgo is that it exposes extremely little in terms of a public API. Just the function name mangling scheme and a couple of types (I had no luck with __go_slice, BTW). But there is a huge public API in the form of the Go language specifications and its included packages.

So the strategy is to use as little as possible directly from libgo and write Go code for the rest. Convincing autoconf and libtool to create a library from Go and C code was not easy, because they mostly lack builtin gccgo support, but it was done.

When building this library and programs using it, it's important to leave the debug info unstripped because the Go runtime needs it. So use '-g' in your CFLAGS and make sure you don't have '-s' in LDFLAGS (already done in golib's build system) and if you're a distribution packager make sure that the installed binaries are excepted from stripping, like in the Gentoo ebuild.

Don't be alarmed by the use of Pthreads. libgo only uses it for mutexes, the coroutines are proper user-space M:N coroutines just like in Go.

build

./autogen.sh
./configure
make

run tests

make check

benchmarks

/usr/bin/time -v ./benchmarks/cw-c
/usr/bin/time -v ./benchmarks/cw-go

With the chinese whispers benchmark I see on my system (gcc-8.2.0, go-1.11, AMD FX-8320E, Linux 4.18.7 x86_64) that the golib version is 4.3 times slower and uses 4.1 times more memory than the Go version. This should be a worst case scenario since the benchmark creates 500000 goroutines and then passes integers from one to the other, incrementing them with each pass. So it's basically testing the concurrency and message passing overhead. But look at the bright side: when gccgo improves, golib will reap the benefits ;-)

Instructions for building with non-default compilers:

./configure CC=gcc-7.1.0 GOC=gccgo-7.1.0
make clean
make

API docs

See the benchmarks and tests. We'll have proper documentation once the API is stable. Right now it's more of a technical preview.

It might be worth noting that we pass pointers through the channels and they should point to heap allocated memory. Since I didn't figure out how to make the standard library's malloc() play nice with Go's garbage collector, you should use the latter exclusively by replacing malloc() with go_malloc().

With recent GCC versions it's necessary to replace all assignments having a heap pointer in the right side with calls to writebarrierptr(). Even when the destination is on stack, due to how the new Go garbage collector is implemented.

TODO

Move as much code as possible from C (where we're chasing the moving target that is GCC libgo's private API) to Go that has a much more stable API in the language specifications.

license

BSD-2

credits

• author: Ștefan Talpalaru stefantalpalaru@yahoo.com

• homepage: https://github.com/stefantalpalaru/golib