cmd/go: go env discards all but the first word of $CC

[AxbB36]

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

go1.6.2

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

linux/386

If you try to stuff extra arguments into the CC environment variable, go env will throw them away (here, bar is discarded):

go1.6.2$ CC="foo bar" ./bin/go env
...
CC="foo"
GOGCCFLAGS="-fPIC -m32 -pthread -fmessage-length=0"

Earlier releases, for example 1.4.3, also remove arguments from CC, but keep them in a separate variable, GOGCCFLAGS:

go1.4.3$ $ CC="foo bar" ./bin/go env
...
CC="foo"
GOGCCFLAGS="bar -fPIC -m32 -pthread -fmessage-length=0"

The code responsible for this shuffling lies in the mkEnv function in env.go:
https://github.com/golang/go/blob/go1.4.3/src/cmd/go/env.go#L55-L56

        env = append(env, envVar{"CC", cmd[0]})
        env = append(env, envVar{"GOGCCFLAGS", strings.Join(cmd[3:], " ")})

(Indices 1 and 2 are skipped because they are inserted by ccompilerCmd in build.go.) Note that mkEnv ignores any previous value of GOGCCFLAGS.

b38fa89 is the commit that caused the behvior to change, by calling mkEnv an extra time and overwriting environment variables with its output. Since one application of mkEnv does this:

CC ← CC[0]
GOGCCFLAGS ← CC[1:] -fPIC -m32 -pthread -fmessage-length=0

two applications have the effect of discarding CC[1:]:

CC ← CC[0]
GOGCCFLAGS ← -fPIC -m32 -pthread -fmessage-length=0

Why this matters to me: I'm cross-compiling using a specially installed GCC that needs extra -I and -L flags to find its files. (Specifically, I'm doing a cross build from linux to darwin for Tor Browser; see here for details.) I'm running this command, which worked with 1.4.3:

CGO_ENABLED=1 CC_FOR_TARGET="$CC $CFLAGS $LDFLAGS" CC= CFLAGS= LDFLAGS= ./make.bash

($CC is the cross compiler.) But because make.bash calls dist env, the necessary $CFLAGS and $LDFLAGS disappear and the build fails somewhere in cgo because the compiler cannot find errno.h.
#13377 is a related issue, particularly this comment that talks about "only using the first word of $CC." As a workaround I'm using a suggestion from that ticket: I'm making a shell script called cc-for-target that contains exec $CC $CFLAGS $LDFLAGS "$@" and invoking make.bash with CC_FOR_TARGET=cc-for-target.

[AxbB36]

This is what I did to find that b38fa89 was the commit that changed behavior.

git bisect start
git bisect new go1.6.2
git bisect old go1.4.3
git bisect run ../check.sh

where check.sh contains:

#!/bin/sh
git clean -df
(cd src && CGO_ENABLED=0 ./make.bash) || exit 125
CC='gcc XYZ' ./bin/go env | grep XYZ
exit $?

[dominikh]

See also #11685

[davmaz]

Ian -
Have you looked into this. It's killing my cross compile now because of this problem. Is there any work-around? I don't quite understand the one mentioned above.

Thanks -
Dave

[ianlancetaylor]

@davmaz I have not looked into this at all. As far as I know it only affects go env output.

In any case it appears that a simple workaround for now is to store your command line in an executable shell script, and set CC to that shell script.

[davmaz]

I guess I'll have to find a way. But it does not just effect "go env", it changes the compiler calls (ignores the exported values after the first) and puts in new ones that wreck the cross-compile. I'm surprised more user haven't complained, but I understand. I'll just have to find a way around it if I want to stay current with the latest go version.

[ianlancetaylor]

@davmaz This issue just talks about go env. If this affects more than that, can you show the problem in detail, or open a new issue for the problem you are having? Thanks.

[davmaz]

Ian,
I think it may involve more than go env. My problem is with cross-compiling a popular C/Fortran library called OpenBLAS. Here's what I did:

I've got the OpenBLAS make to cross-compile the library by doing this:

• Find all installed packages for the ARM compiler: sudo aptitude search arm-linux-gnueabi
• Purge ALL gnueabi versions: sudo apt-get purge --auto-remove gfortran-arm-linux-gnueabi, etc for any "installed"
• Install only gnueabihf versions: sudo aptitude install gfortran-arm-linux-gnueabihf (this also installs gnueabihf gcc)
• From the OpenBLAS directory: make CC=arm-linux-gnueabihf-gcc FC=arm-linux-gnueabihf-gfortran HOSTCC=gcc TARGET=CORTEXA9
• Install the ARM libs: sudo make PREFIX=/usr/local install

The make runs to completion and I can install the ARM OpenBLAS library. I followed similar steps to get FFTW to cross-compile if anyone is interested.

Next, installing go for cross-compiling I did this:

• export CGO_ENABLED=1
• export CC_FOR_TARGET=arm-linux-gnueabihf-gcc
• export GOGCCFLAGS="-fPIC -pthread -mfpu=vfp -mfloat-abi=hard --static"
• export GOOS=linux
• export GOARCH=arm
• export GOARM=7
• bash ./all.bash

• go env shows:

• GOARCH="arm"
• GOBIN=""
• GOEXE=""
• GOHOSTARCH="amd64"
• GOHOSTOS="linux"
• GOOS="linux"
• GOPATH="/opt/Projects/Golang"
• GORACE=""
• GOROOT="/usr/local/go"
• GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
• CC="arm-linux-gnueabihf-gcc"
• GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build149148529=/tmp/go-build -gno-record-gcc-switches"
• CXX="g++"
• CGO_ENABLED="1"

Notice the GOGCCFLAGS get mangled (see golang go issues 8161). I can work around that by specifying GOGCCFLAGS on the command line:
GOOS=linux GOARCH=arm GOARM=7 GOGCCFLAGS="-fPIC -pthread -mfpu=vfp -mfloat-abi=hard --static" CC=arm-linux-gnueabihf-gcc CGO_LDFLAGS="-L/usr/local/lib -lopenblas " go build -x rand_zgeev.go

However, when I copy this to the arm system, it does not run:
./rand_zgeev
-sh: ./rand_zgeev: not found

Any ideas why this won't run?

---

From: Ian Lance Taylor [notifications@github.com]
Sent: Thursday, August 04, 2016 18:51
To: golang/go
Cc: davem@ltsnet.net; Mention
Subject: Re: [golang/go] cmd/go: go env discards all but the first word of $CC (#15457)

@davmazhttps://github.com/davmaz This issue just talks about go env. If this affects more than that, can you show the problem in detail, or open a new issue for the problem you are having? Thanks.

—
You are receiving this because you were mentioned.
Reply to this email directly, view it on GitHubhttps://github.com//issues/15457#issuecomment-237707818, or mute the threadhttps://github.com/notifications/unsubscribe-auth/AAgSBmJOyHpR6JZxYalVP8M2gg97nHi4ks5qcmzxgaJpZM4IQdm1.

[ianlancetaylor]

@davmaz Let's please take that part of the conversation to a forum (see https://golang.org/wiki/Questions) or a separate issue, rather than complicating this issue. Thanks.

[davmaz]

Sorry Ian. I didn't know how to get back there. Thanks for the link.

---

From: Ian Lance Taylor [notifications@github.com]
Sent: Monday, August 08, 2016 16:20
To: golang/go
Cc: davem@ltsnet.net; Mention
Subject: Re: [golang/go] cmd/go: go env discards all but the first word of $CC (#15457)

@davmazhttps://github.com/davmaz Let's please take that part of the conversation to a forum (see https://golang.org/wiki/Questions) or a separate issue, rather than complicating this issue. Thanks.

—
You are receiving this because you were mentioned.
Reply to this email directly, view it on GitHubhttps://github.com//issues/15457#issuecomment-238363658, or mute the threadhttps://github.com/notifications/unsubscribe-auth/AAgSBpYXKQHp9ISi2khqg2Q9PSqJZSa3ks5qd4-VgaJpZM4IQdm1.

[rsc]

/cc @quentinmit

[gopherbot]

CL https://golang.org/cl/33293 mentions this issue.