misc/cgo/testcdefs doesn't work: C source files not allowed when not using cgo

[keithkml]

I'm new to Go, and I'm attempting to learn about how to interoperate between C and Go. I thought a good way to learn would be to go through some of the examples in the repo. However it appears that a change in Go 1.4 has made one of the examples not work anymore. Others seem to be having related issues: #9132

https://github.com/golang/go/tree/master/misc/cgo/testcdefs

$ go version
go version go1.4 darwin/amd64
$ cd misc/cgo/testdefs
$ ./test.bash 
can't load package: package .: C source files not allowed when not using cgo: cdefstest.c main.c

[ianlancetaylor]

You're right: testcdefs doesn't work any more, and we should fix that or delete the directory.

That said, that directory is not an example of how to interoperate between C and Go. It's a test of the -cdefs option of the cgo tool, which is not intended for use by anybody other than people bootstrapping a Go port to a new operating system.

[keithkml]

Hi @ianlancetaylor, remember me from the Berkeley google shuttle? :)

I guess I was mistaken about the purpose of that directory – the blog post at http://blog.golang.org/c-go-cgo links to misc/cgo with the phrase "The cgo examples in the Go tree demonstrate more advanced concepts."

[keithkml]

I'm brand new to Go, and made the mistake of getting my feet wet by attempting to call into Go from an existing C++-based mobile app :) Probably should've started with something simpler.

The docs seem to thoroughly cover how to call into C from Go, but not the other way around...

[ianlancetaylor]

Unfortunately at present you have to start with a Go program. There is as yet no support for calling a Go library from a C/C++ program.

It is possible to have a Go program that calls C code that calls Go code, though (http://golang.org/cmd/cgo/#hdr-C_references_to_Go).