x/sys: x/sys/unix doesn't work with gccgo on arm #23361

syscall_linux_arm_gccgo.go.gz

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

go version go1.8.3 gccgo (GCC) 7.2.1 20171128 linux/arm

Does this issue reproduce with the latest release?

yes with git HEAD version

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

GOARCH="arm"
GOBIN=""
GOEXE=""
GOHOSTARCH="arm"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/chri/go"
GORACE=""
GOROOT="/usr"
GOTOOLDIR="/usr/lib/gcc/armv5tel-unknown-linux-gnueabi/7.2.1"
GCCGO="/usr/bin/gccgo"
GOARM=""
CC="/usr/bin/gcc"
GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build749168280=/tmp/go-build -gno-record-gcc-switches"
CXX="/usr/bin/g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

Tried to use golang.org/x/sys/unix in a simple test program. go builded it.

What did you expect to see?

Nothing, because it should build

What did you see instead?

/tmp/go-build003625631/golang.org/x/sys/libunix.a(go.o): In function golang_org_x_sys_unix.Seek': /home/chri/go/src/golang.org/x/sys/unix/syscall_linux_arm.go:51: undefined reference to golang_org_x_sys_unix.seek'
collect2: error: ld returned 1 exit status

The problem is that seek syscall (and a bunch of others) are implemented through a function defined in asm_linux_arm.s which calls into the runtime. I think the problem is that the assembler code is not compatible with gccgo (i.e. binutils) and also I doubt the function is implemented in the gccgo runtime because of the strange name syscall·seek(SB)

A quick fix is attached, I reimplemented the syscall in a gccgo friendly way. I doubt the allocation is a big performance problem (as noted in syscall_linux_arm.go). But I didn't want to touch existing files, so I just prepared the drop-in file I am attaching. If you think this is the right way to fix the problem, I can prepare a patch for review.

Thanks!