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cmd/go: import "C" breaks cross-compiling to Linux in OSX #19470

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prasincs opened this issue Mar 9, 2017 · 1 comment
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cmd/go: import "C" breaks cross-compiling to Linux in OSX #19470

prasincs opened this issue Mar 9, 2017 · 1 comment
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.

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@prasincs
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prasincs commented Mar 9, 2017 •
edited

Please answer these questions before submitting your issue. Thanks!

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

go version go1.8 darwin/amd64

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

OSX 10.12.3

Darwin Wintermute.local 16.4.0 Darwin Kernel Version 16.4.0: Thu Dec 22 22:53:21 PST 2016; root:xnu-3789.41.3~3/RELEASE_X86_64 x86_64 i386 MacBookPro11,5 Darwin

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/pgautam/go"
GORACE=""
GOROOT="/Users/pgautam/go-src"
GOTOOLDIR="/Users/pgautam/go-src/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/sj/n5_cngpx27xd0cxrqry3j65h0000gn/T/go-build807902586=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
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?

I created a file in a package proj with import "C" where C is never referenced in the code.

package proj

import "C"
import "fmt"

func Hello() {
        fmt.Println("Hello There!")
}

Then I made a main.go file with the following contents

-> % cat main.go
package main

import "github.com/prasincs/testproject/proj"

func main() {
        proj.Hello()
}

go build -o testproject . works as expected

but cross compiling fails

-> % GOOS=linux go build -o testproject  .
main.go:3:8: no buildable Go source files in /Users/pgautam/go/src/github.com/prasincs/testproject/proj

If I explicitly set CGO_ENABLED=1, I get an error at link time

-> % CGO_ENABLED=1 GOOS=linux go build -o testproject .
# runtime/cgo
ld: unknown option: --build-id=none
clang: error: linker command failed with exit code 1 (use -v to see invocation)

What did you expect to see?

I was expecting the following:

  • C is never used in the code but it is imported, that should be an error at build time
  • If the previous point is expected behavior, it should work with GOOS=linux enabled too.
  • CGO_ENABLED=1 should work if the issue is with cgo being turned off at cross-compile time.

What did you see instead?

I got the following instead of an error message regarding the spurious import "C" or a cross-compiled binary.

main.go:3:8: no buildable Go source files in /Users/pgautam/go/src/github.com/prasincs/testproject/proj
@ALTree ALTree changed the title import "C" breaks cross-compiling to Linux in OSX cmd/go: import "C" breaks cross-compiling to Linux in OSX Mar 9, 2017
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Mar 9, 2017
@robpike
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robpike commented Mar 9, 2017

Cgo is not portable and cannot in general be used for cross-compilation as it requires the availability of C libraries on the target platform.

Sorry about this, but it's working as intended.

@robpike robpike closed this as completed Mar 9, 2017
@golang golang locked and limited conversation to collaborators Mar 9, 2018
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@prasincs @ALTree @robpike @gopherbot