Go 1.16 beta1: ios/amd64 build fails

[marten-seemann]

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

$ go version
go version go1.16beta1 darwin/amd64

What did you do?

I have a cross-compilation test which I run on CI. It builds a binary for all supported GOOS / GOARCH combinations (as reported by go tool dist list).

Using Go 1.15.x, GOOS=ios GOARCH=amd64 is unsupported:

cmd/go: unsupported GOOS/GOARCH pair ios/amd64

Go 1.16 apparently adds support, but building fails. On my Mac, the error message is the following:

❯ GOOS=ios GOARCH=amd64 go build example/main.go
# command-line-arguments
loadinternal: cannot find runtime/cgo

On CI (GitHub Actions), I'm getting the following failure:

# command-line-arguments
loadinternal: cannot find runtime/cgo
/opt/hostedtoolcache/go/1.16.0-beta1/x64/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
/usr/bin/ld: cannot find 1144: No such file or directory
/tmp/go-link-046955828/go.o: file not recognized: file format not recognized
collect2: error: ld returned 1 exit status

Not sure what exactly this means, nor do I particularly care about building for this architecture. However, if go tool dist list lists this as a support combination, I would have expected the build to succeed.

What did you expect to see?

go build should succeed.

What did you see instead?

go build failed, see above.

[egonelbre]

Maybe you need an explicit CGO_ENABLED=1?

[marten-seemann]

The code I’m building doesn’t use cgo, and the build settings I’m using work fine for all other combinations.

[egonelbre]

Ah, now I understand. It's using amd64 and not arm64.

• ios/amd64 was added in https://go-review.googlesource.com/c/go/+/263798.
• some of the misc/ios instructions were updated in https://go-review.googlesource.com/c/go/+/255257/.

https://github.com/golang/go/tree/master/misc/ios has instructions how to use it.

[egonelbre]

Also using CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build example.go does work on the tip and with go1.16beta1. So it seems CGO_ENABLED is required, regardless whether you are using C.

[egonelbre]

CC @eliasnaur.

[egonelbre]

Maybe it needs to make CGO_ENABLED default to 1 for that platform or throw an error when it has not been enabled -- no clue where it should go though.

[eliasnaur]

I'm not sure either. CC @cherrymui.

[cherrymui]

Yeah, CGO_ENABLED needs to be set to 1, because currently the ios port requires external linking, which uses the C linker.

loadinternal: cannot find runtime/cgo

This is not an error. It should generate the executable and it probably runs fine.

CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build example.go does work on the tip and with go1.16beta1.

Could you explain what doesn't work?

[cherrymui]

CGO_ENABLED is default to 0 for cross-compilation. It may be reasonable to error out on ports require cgo.

[egonelbre]

@cherrymui Erroring sounds less "risky" because it can be made to work later. I would create a change, but I have no clue where the appropriate place would be. (Also, probably faster if someone else who knows where and how to exactly restrict it.)

[cherrymui]

Erroring sounds less "risky" because it can be made to work later.

Yeah, I think it shouldn't be hard to make internal linking work for iOS, then you don't need the C linker. Maybe in Go 1.17. Not sure it is that useful, though, since for actual iOS apps I think it generally needs some C (or other language) part.

That said, I think it's been the case for quite a while (CGO_ENABLED stuff for cross-compilation). As we're late in the release cycle, maybe it's better to do the erroring behavior in Go 1.17. This probably will be in cmd/go, but I'm not sure exactly where. Issue #31544 might be relevant (about the loadinternal message).

[cherrymui]

@egonelbre could you clarify if CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build works? (This is the primary issue) On my Mac it works fine.

$ CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build hello.go
$ ./hello
hello

[egonelbre]

@churrymui Yes CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build works.

The main issue is that GOOS=ios GOARCH=amd64 go build gives a really weird error - so it would be better to print out CGO_ENABLED=1 is required for ios/amd64 or alternatively add CGO_ENABLED=1 automatically.

[enty8080]

@cherrymui:

root@Ivans-Air work # ls
build.sh	main-ios	main.go
root@Ivans-Air work # rm main-ios
root@Ivans-Air work # CGO_ENABLED=1 GOOS=ios GOARCH=amd64 go build main.go 
# runtime/cgo
gcc_darwin_amd64.c:62:15: error: unknown token in expression
<inline asm>:1:12: note: instantiated into assembly here
gcc_darwin_amd64.c:62:15: error: invalid operand
<inline asm>:1:12: note: instantiated into assembly here
root@Ivans-Air work # ls
build.sh	main.go

What I should do with this?

[eliasnaur]

@enty8080 your go build command worked for egonelbre and cherrymui, so what's unusual about your setup? Are you building on an iDevice? What does go env say, and what about clang -v?

[enty8080]

@eliasnaur root@Ivans-Air work # means that I building from MacBook Air.

go version

go version go1.16beta1 darwin/arm64

clang -v

Apple clang version 12.0.0 (clang-1200.0.32.28)
Target: arm64-apple-darwin20.1.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

go env

GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/enty8080/Library/Caches/go-build"
GOENV="/Users/enty8080/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/enty8080/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/enty8080/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.16beta1"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/mp/l216mspj1r793n3f2zhh8vg40000gn/T/go-build1298098095=/tmp/go-build -gno-record-gcc-switches -fno-common"

[eliasnaur]

I don't know the reason for your error. FWIW, Rob may have had the same issue:

I also have to set CGO_ENABLED=0 because of an assembly language syntax error (something about [reg] notation) that stops the build.

[enty8080]

@eliasnaur I am using latest MacBook Air:

[cherrymui]

See https://tip.golang.org/misc/ios/README . For cross compilation in general, you need to set CC to the C cross compiler.

[enty8080]

@cherrymui Thanks, I answered here #43371

[gopherbot]

Change https://golang.org/cl/280154 mentions this issue: doc/go1.16: reference misc/ios/README for how to build iOS programs

[gopherbot]

Change https://golang.org/cl/280153 mentions this issue: misc/ios: add to README how to build ios executables

[cherrymui]

From #43343 (comment) the ios/amd64 build works, so this issue is resolved.

I'll look into erroring out when cgo is not enabled (not necessarily in this release, though).