gccgo: Trouble cross-compiling to GOARCH=mips using gccgo

[elimisteve]

What version of Go are you using (go version)?

go version go1.8rc3 linux/amd64

What operating system and processor architecture are you using (go env)?

linux/amd64

What did you do?

I tried cross-compiling a trivial "hello world" Go program -- namely https://github.com/elimisteve/hello/blob/master/hello.go -- with this command:

$ GOOS=linux GOARCH=mips go1.8rc3 build -x -compiler=gccgo .

What did you expect to see?

No output and a successfully-compiled 32-bit MIPS binary in my local directory.

What did you see instead?

$ GOOS=linux GOARCH=mips go1.8rc3 build -x -compiler=gccgo .
WORK=/tmp/go-build262885004
mkdir -p $WORK/github.com/elimisteve/hello/_obj/
mkdir -p $WORK/github.com/elimisteve/hello/_obj/exe/
cd /home/ubuntu/go/src/github.com/elimisteve/hello
/usr/bin/gccgo -I $WORK -c -g -mabi=32 -march=mips32 -fgo-relative-import-path=_/home/ubuntu/go/src/github.com/elimisteve/hello -o $WORK/github.com/elimisteve/hello/_obj/_go_.o ./hello.go
# github.com/elimisteve/hello
gccgo: error: unrecognized argument in option ‘-mabi=32’
gccgo: note: valid arguments to ‘-mabi=’ are: ms sysv

This is using gccgo 6, which installed 'libgo9as a dependency when I ranapt-get install gccgo`.

At https://tip.golang.org/doc/install/gccgo it says,

The GCC 6 releases include a complete implementation of the Go 1.6.1 user libraries. The Go 1.6 runtime is not fully merged, but that should not be visible to Go programs.

so I believe this is supposed to work? Thanks!

[cherrymui]

It looks like your gccgo isn't the cross compiler, i.e. it's targeting the host (amd64) instead of mips. I don't know how to cross compile with gccgo though. You probably needs to set up some environment variable.

[cherrymui]

Maybe apt-get install gccgo-mips-linux-gnu?

[minux]

and you should use the go tool bundled with gccgo, not go tool bundled with gc due to various version skew problems.

[elimisteve]

@minux Well the key line seems to be

/usr/bin/gccgo -I $WORK -c -g -mabi=32 -march=mips32 -fgo-relative-import-path=_/home/ubuntu/go/src/github.com/elimisteve/hello -o $WORK/github.com/elimisteve/hello/_obj/go.o ./hello.go

which is using gccgo directly. Not sure if I should try xgo or whether building my own cross-compiling version of GCC, a la https://github.com/golang/go/wiki/GccgoCrossCompilation#build-the-cross-compiler, is necessary.

[minux]

I'm pretty sure /usr/bin/gccgo is not a mips cross gccgo. As cherrymui mentioned, you need to install a cross gccgo, and then use the go command bundled with cross gccgo.

[ianlancetaylor]

Setting GOOS and GOARCH when running the go tool works to do cross-compiling with the gc toolchain, but it does not work when using the gccgo toolchain. It would be nice to make this work better, but it will never be as simple as it is with the gc toolchain.

[jsw-davidhuang]

1. sudo apt-get install gccgo-mipsel-linux-gnu
2. mipsel-linux-gnu-gccgo -o main main.go

[adonespitogo]

This is my first time using gccgo and just wanting to cross-compile my go app for openwrt. Can anyone please tell me why importing non-standard package fails?

mipsel-linux-gnu-gccgo -o app ./main/main_mono.go
./main/main_mono.go:5:36: error: import file ‘github.com/my-private/package’ not found
    5 | import "github.com/my-private/package"

github.com/my-private/package is just arbitrary package name for confidentiality reasons. I am able to build this go program using standard go build command.

[cherrymui]

@adonespitogo you're expected to use the go command that comes with gccgo, instead of the gccgo command directly. For cross-compilation, you might be able to do something like GOOS=linux GOARCH=mips GCCGO=mipsel-linux-gnu-gccgo CC=<your-C-cross-compiler> go build -compiler=gccgo

[adonespitogo]

Thanks for the advice @cherrymui . I tried CGO_ENABLED=0 GOOS=linux GOARCH=mips GCCGO=mipsel-linux-gnu-gccgo go build -tags="mono dev" -compiler=gccgo but now I have a different error:

package io/fs is not in GOROOT (/home/adonesp/.gvm/gos/go1.19.4/src/io/fs)

[ianlancetaylor]

Make sure that you are using the go command that comes with gccgo, not the one that comes with the usual gc distribution.

Make sure that GOROOT is not set in the environment.

[adonespitogo]

My gccgo installation from ubuntu apt repository does not seem to have go command installed with it. I'm now compiling gcc go from the source. Will report back with the result.

[adonespitogo]

I've built gccgo from scratch following https://go.dev/doc/install/gccgo and now I have the go command from gccgo. Now I encounter another problem:

export GOOS=linux                                                                                                                                                                                
export GOARCH=mips                                                                                                                                                                               
export GCCGO=mipsel-linux-gnu-gccgo

/opt/gccgo/bin/go build -tags="mono dev" -compiler=/opt/gccgo/bin/gccgo -gccgoflags -Wl,-R,/opt/gccgo/lib64/ -static-libgo -o myapp.app main.go
/opt/gccgo/bin/go: error while loading shared libraries: libgo.so.21: cannot open shared object file: No such file or directory

❯ ls /opt/gccgo/lib64 | grep libgo.so
libgo.so
libgo.so.21
libgo.so.21.0.0

[adonespitogo]

It's working now, I guess. Here's my new env and build params:

export GOOS=linux
export GOARCH=mips
export GCCGO=/usr/bin/mips-linux-gnu-gccgo
export LD_LIBRARY_PATH=/opt/gccgo/lib64

/opt/gccgo/bin/go build -tags="mono dev" -compiler=gccgo -gccgoflags -Wl,-R,/opt/gccgo/lib64

Though I can't confirm it yet since I still have to update my go codes to use golang go1.18 instead of go1.19.