cmd/go: handle pkg-config output containing spaces

[ktsakas]

I am using Go v1.6.2 on Windows 10.
I tried to build the git2go package in MinGW-w64 using go build but it fails.
When I run go build -x, I get the following:

CGO_LDFLAGS="-g" "-O2" "-LC:/Program" "Files" "(x86)/libgit2/lib" "-lgit2" 
"C:\\Go\\pkg\\tool\\windows_amd64\\cgo.exe" -objdir 
"C:\\msys64\\tmp\\go-build610654106\\github.com\\libgit2\\git2go\\_obj\\" 
-importpath github.com/libgit2/git2go -- Files (x86)/libgit2/include 
-IC:/Program -I "C:\\msys64\\tmp\\go-build610654106\\github.com\\libgit2\\git2go\\_obj\\" 
blame.go blob.go branch.go checkout.go cherrypick.go clone.go commit.go 
config.go credentials.go describe.go diff.go git.go graph.go 
handles.go ignore.go index.go merge.go note.go object.go odb.go packbuilder.go 
patch.go refdb.go reference.go remote.go repository.go reset.go revparse.go settings.go 
signature.go status.go submodule.go tag.go tree.go walk.go
# github.com/libgit2/git2go
gcc: error: Files: No such file or directory
gcc: error: (x86)/libgit2/include: No such file or directory

Notice how "-LC:/Program" "Files" "(x86)/libgit2/lib" flag is split up on every space and the parts are put in quotes, which seems to cause the issue.
I understand that mingw has problems with spaces in paths, however this should be fixable in build.go.

The issue has been mentioned again in git2go#155.

[0xmohit]

This appears to be the same as #7906.

[mattn]

This is related #11868.

[quentinmit]

It looks like those CGO_LDFLAGS are coming from git.go:

#cgo pkg-config: libgit2

Can you please try running pkg-config --debug --libs libgit2 and let me know the complete output?

I would like to know if we're misparsing the output of pkg-config, or if it is not outputting the correctly-escaped string.

[rsc]

We are certainly misparsing the output of pkg-config, since we use strings.Fields. There's no way that can possibly handle a path like C:/Program Files correctly. The question is how the output is defined so that we can parse it correctly.

On Linux, I get:

$ cat /tmp/whitespace.pc
prefix=/usr
exec_prefix=${prefix}
libdir="${exec_prefix}/white space/lib"
includedir="${prefix}/white space/include"

Name: Whitespace test
Description: Dummy pkgconfig test package for testing pkgconfig
Version: 1.0.0
Requires:
Libs: -L${libdir} -lfoo\ bar "-lbar baz" -r:foo 
Cflags: -I${includedir} -I$(top_builddir) -Iinclude\ dir "-Iother include dir" -Dlala=misc
$ PKG_CONFIG_PATH=/tmp pkg-config --libs whitespace
-r:foo -L/usr/white\ space/lib -lfoo\ bar -lbar\ baz  
$ 

That is, on Linux pkg-config seems to escape spaces with a backslash. We don't handle that (and we should), but if pkg-config on Windows were emitting those, we'd see them in the CGO_LDFLAGS print, and we don't. For example, if I continue on Linux:

$ cat x.go
package main

/*
#cgo pkg-config: whitespace
*/
import "C"

func main() {}

$ PKG_CONFIG_PATH=/tmp go build -x x.go
WORK=/tmp/go-build540380321
mkdir -p $WORK/command-line-arguments/_obj/
mkdir -p $WORK/command-line-arguments/_obj/exe/
cd /usr/local/google/home/rsc
pkg-config --cflags whitespace
pkg-config --libs whitespace
CGO_LDFLAGS="-g" "-O2" "-r:foo" "-L/usr/white\\" "space/lib" "-lfoo\\" "bar" "-lbar\\" "baz" ./go/pkg/tool/linux_amd64/cgo -objdir $WORK/command-line-arguments/_obj/ -importpath command-line-arguments -- -Dlala=misc "-I/usr/white\\" space/include -I$(top_builddir) "-Iinclude\\" dir "-Iother\\" "include\\" dir -I $WORK/command-line-arguments/_obj/ x.go
# command-line-arguments
gcc: error: space/include: No such file or directory
gcc: error: dir: No such file or directory
gcc: error: include\: No such file or directory
gcc: error: dir: No such file or directory
$ 

So it looks like, even if we were handling spaces correctly on Linux, handling them correctly on Windows would require different code.

The big question, then, is what pkg-config prints on Windows. It would be great if it printed one arg per line or something like that, so we could split at newline.

@ktsakas, can you please send the output of

pkg-config --cflags libgit2
pkg-config --libs libgit2

on your Windows machine?

Thanks.

[quentinmit]

@ktsakas I tried installing MinGW-w64 and MSys2 to debug this, only to discover that their libgit2 package is installed to /mingw64/include. How did you end up with libgit2 in C:\Program Files (x86)\libgit2?

[mattn]

As far as I try this on msys2 on my environment,

backslash separator

prefix=c:\Program Files (x86)\libgit
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: foo
Version: 1.2.3
Description: libfoo
URL: http://example.com
Libs: -L${libdir} -lfoo
Cflags: -I${includedir}

$ pkg-config --cflags foo
Files (x86)libgit/include -Ic:Program

slash separator

prefix=c:/Program Files (x86)/libgit
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: foo
Version: 1.2.3
Description: libfoo
URL: http://example.com
Libs: -L${libdir} -lfoo
Cflags: -I${includedir}

$ pkg-config --cflags foo
Files (x86)/libgit/include -Ic:/Program

backslash escaped

prefix=c:/Program\ Files\ (x86)/libgit
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: foo
Version: 1.2.3
Description: libfoo
URL: http://example.com
Libs: -L${libdir} -lfoo
Cflags: -I${includedir}

$ pkg-config --cflags foo
-Ic:/Program\ Files\ (x86)/libgit/include

quoted includedir

prefix=c:/Program Files (x86)/libgit
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir="${prefix}/include"

Name: foo
Version: 1.2.3
Description: libfoo
URL: http://example.com
Libs: -L${libdir} -lfoo
Cflags: -I${includedir}

$ pkg-config --cflags foo
-Ic:/Program\ Files\ (x86)/libgit/include

[rsc]

@ktsakas we are waiting on more info from you about pkg-config on your Windows system.

In the meanwhile, we will fix the Unix case and leave Windows using strings.Fields.