crypto/x509: cgo errors when compiling with gcc on Darwin

[avinashrd]

Please answer these questions before submitting your issue. Thanks!

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

1.10

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN="/Users/xxx/Downloads/projects/golang/bin"
GOCACHE="/Users/xxx/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/xxx/Downloads/projects/golang"
GORACE=""
GOROOT="/usr/local/opt/go/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/opt/go/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="/usr/local/Cellar/gcc/7.3.0_1/bin/gcc-7"
CXX="/usr/local/Cellar/gcc/7.3.0_1/bin/g++-7"
CGO_ENABLED="1"
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=/var/folders/w8/y97pxwvj35xcsw9vmh2s3gzr0000gn/T/go-build575805343=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

ran a simple program

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

func main() {
	urls := make([]string, 3)
	urls[0] = "https://www.usa.gov/"
	urls[1] = "https://www.gov.uk/"
	urls[2] = "//www.gouvernement.fr/"

	for _, u := range urls {
		responseTime(u)
	}
}

func responseTime(url string) {
	start := time.Now()

	res, err := http.Get(url)

	if err != nil {
		log.Fatal(err)
	}

	defer res.Body.Close()

	elapsed := time.Since(start).Seconds()

	fmt.Printf("%s took %v seconds \n", url, elapsed)
}

What did you expect to see?

expected output

What did you see instead?

# crypto/x509
In file included from /System/Library/Frameworks/Security.framework/Headers/AuthSession.h:32:0,
                 from /System/Library/Frameworks/Security.framework/Headers/Security.h:43,
                 from /usr/local/Cellar/go/1.10/libexec/src/crypto/x509/root_cgo_darwin.go:17:
/System/Library/Frameworks/Security.framework/Headers/Authorization.h:193:7: error: variably modified 'bytes' at file scope
  char bytes[kAuthorizationExternalFormLength];
       ^~~~~

[avinashrd]

solved this issues by using clang as the compiler instead of gcc

[odeke-em]

@avinashrd what version of gcc is this?

/cc @ianlancetaylor @FiloSottile

[adamdecaf]

It sounds like gcc 7.3 from the previous issue #24425 (comment)

[admercs]

I had this issue with both gcc 7.3 and 8.1. The issue was resolved by changing the C/C++ compiler environmental variables to Apple clang before running go get commands:

CC="clang" && CXX="clang++"
go get <yourpackagename>

That way, you don't have to modify your bashrc or bash_profile. Defining an alias would also work. The issue appears to be the same as #24425 as mentioned.

[bradfitz]

There's nothing Go-specific here. I see this problem all over the web with different projects.

The code in question is Apple's, and not in Go's codebase anywhere.

At best we could make cmd/go detect this case (on failure, check if using gcc) and then recommend using clang. Might be overkill. @ianlancetaylor?

[ianlancetaylor]

Honestly I think that is overkill. I agree that I don't think there is anything we can reasonably change to make this work, so closing the issue. Please comment if you disagree.