cmd/go: handle space in path to C compiler

[apmckinlay]

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

$ go version
go version go1.15.7 windows/amd64

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

go env Output

$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\andrew\AppData\Local\go-build
set GOENV=C:\Users\andrew\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\andrew\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\andrew\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=V:\gsuneido\go.mod
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\andrew\AppData\Local\Temp\go-build158816006=/tmp/go-build -gno-record-gcc-switches
GOROOT/bin/go version: go version go1.15.7 windows/amd64
GOROOT/bin/go tool compile -V: compile version go1.15.7
gdb --version: GNU gdb (GDB) 8.1

What did you do?

> go build -v -ldflags "-s -w -X 'main.builtDate=Jan 20 2021 11:17:27' -X main.mode=gui -H windowsgui"

What did you expect to see?

Successful build

What did you see instead?

# github.com/apmckinlay/gsuneido/builtin/goc
cgo: exec c:\Program: exec: "c:\\Program": file does not exist

It builds successfully on 1.15.6 (and 1.16beta1)

I cut my path down to:

PATH=C:\WINDOWS\System32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\system32;C:\Program Files\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin;C:\Go\bin;C:\Users\andrew\go\bin

In particular, mingw-w64 is in c:\program files
I think that was the default, but I can't remember for sure.

Cmd finds g++ using this path

> g++ --version
g++ (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0

[apmckinlay]

I'm not sure this is the same as #41400 although it could be related.
My problem just started with 1.15.7.
That issue appears to affect older versions.
I don't have an external CC environment variable
My go env CC is just "gcc", no spaces.

[AlexRouSg]

@apmckinlay sorry for missing that it started with 1.15.7

Then this looks due to the security fix in #43785

[apmckinlay]

@AlexRouSg That's what I was assuming

[AlexRouSg]

After reading the patches ... it looks like it sets the CC env var to the full path which contains spaces and thus triggering #41400
e8e7fac#diff-fec5b487b6c6e4cfdbf1e8af384e463d03693a05feb2f9b9a757feb0ab12e1e4R2028

So it does look like fixing #41400 would fix this too. Tho I'm not too sure what route it would eventually take.

cc @bcmills @rolandshoemaker

[rsc]

Apologies. The workaround is to use c:\progra~1 in your path for now.

[apmckinlay]

@rsc No worries, thanks.

[zzwx]

Imagining a new user downloading fresh go version and bumping into inability to compile anything that requires "cgo"

[dmitshur]

@rsc This is a release blocker and doesn't have an assignee right now. Are you planning to work on it, or should someone else? Thanks.

[jayconrod]

I can take a look at this.

I was able to reproduce it on macOS by the way. It looks like it's an issue with spaces in the CC variable passed to cgo, not specifically a Windows issue.

This will likely need to be backported, so I'd rather not attempt a complete fix for #41400 yet.

[bcmills]

@jayconrod, if the alternative approach in #41400 (comment) doesn't work out, another interim mitigation on Windows in particular might be to use GetShortPathName to obtain the space-free version of the path that Russ suggested as a workaround in #43808 (comment).

[gopherbot]

Change https://golang.org/cl/285873 mentions this issue: cmd/go: don't lookup the path for CC when invoking cgo

[jayconrod]

It looks like the alternative approach works out. It just means we revert CL 284780. That was part of the security fix, but it was a "belt and suspenders" fix, and we still have the belt: internal/execabs prevents cgo from using CC with relative paths in PATH.

[jayconrod]

@gopherbot Please backport to 1.14 and 1.15. This was a regression.

[gopherbot]

Backport issue(s) opened: #43859 (for 1.14), #43860 (for 1.15).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.