cmd/go: link should stop when cgo is required but disabled

[perillo]

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

$ go version
go version go1.16.4 linux/amd64

Does this issue reproduce with the latest release?

Yes.
It also reproduces with go1.17 devel.

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

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN="/home/manlio/.local/bin"
GOCACHE="/home/manlio/.cache/go-build"
GOENV="/home/manlio/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE="*.local"
GOMODCACHE="/home/manlio/.local/lib/go/pkg/mod"
GONOPROXY=""
GONOSUMDB="*.local"
GOOS="linux"
GOPATH="/home/manlio/.local/lib/go:/home/manlio/src/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.4"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
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 -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2831720649=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.16.4 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.16.4
uname -sr: Linux 5.12.5-arch1-1
/usr/lib/libc.so.6: GNU C Library (GNU libc) release release version 2.33.
gdb --version: GNU gdb (GDB) 10.2

What did you do?

Using https://play.golang.org/p/LqHgq34kmVq:

$ CGO_ENABLED=0 GOOS=android GOARCH=386 go build

What I'm doing is to check if my package is buildable for the specified platform.

What did you expect to see?

An error, reporting that cgo is required for the platform but explicitly disabled by the user. The program should exit, instead of continuing.

What did you see instead?

loadinternal: cannot find runtime/cgo
/usr/lib/go/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/../../../libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/../../../libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: cannot find libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/../../../libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
collect2: error: ld returned 1 exit status

• android/arm reports:

  loadinternal: cannot find runtime/cgo
  /usr/lib/go/pkg/tool/linux_amd64/link: running gcc failed: exit status 1
  gcc: error: unrecognized command-line option ‘-marm’; did you mean ‘-mabm’?
  

• android/amd64 and android/arm64 works

• ios/amd64 and ios/arm64 reports:

  loadinternal: cannot find runtime/cgo
  /usr/lib/go/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-897956511/go.o: file not recognized: file format not recognized
  collect2: error: ld returned 1 exit status
  

[perillo]

cc @cherrymui @rsc @mdempsky @ianlancetaylor as per owners.

[gopherbot]

Change https://golang.org/cl/321935 mentions this issue: cmd/link: exit if cgo is required for external linking but is disabled

[perillo]

The go tool disables cgo automatically when cross compiling, so it is not necessary to explicitly disable it.