@sillyousu What Linux distribution are you running? Can you please try:

cat <<EOF > foo.pc
Name: foo
Description: The foo library
Version: 1.0.0
Cflags: -Dhello=10 -Dworld=+32 -DDEFINED_FROM_PKG_CONFIG=hello\ world
EOF
PKG_CONFIG_PATH=. pkg-config --cflags foo

and reply with the output from the pkg-config command? This test failure indicates that somehow we lost the backslash after the "hello".

What Linux distribution are you running?
CentOS 6.5/x86_64/2.6.32-431.el6.x86_64

centos65x64TopHighoocwbezz➜  ~ cat <<EOF > foo.pc
heredoc> Name: foo
heredoc> Description: The foo library
heredoc> Version: 1.0.0
heredoc> Cflags: -Dhello=10 -Dworld=+32 -DDEFINED_FROM_PKG_CONFIG=hello\ world
heredoc> EOF
centos65x64TopHighoocwbezz➜  ~ PKG_CONFIG_PATH=. pkg-config --cflags foo
-Dhello=10 -Dworld=+32 -DDEFINED_FROM_PKG_CONFIG=hello world

Okay, so this confirms that your pkg-config did not properly handle the whitespace. CentOS 6.5 appears to include pkg-config 0.23, which dates from 6 years ago. Looking at the source code, it simply has no handling for escape sequences at all. I'm a bit confused though, because it does say in a comment

A '' proceding any other character is ignored and written into the output buffer unmodified.

which does seem like it applies here. Ironically support for whitespace in paths was added later in 2010: https://cgit.freedesktop.org/pkg-config/commit/?id=69a7eaa6

@rsc I'm not sure what to do here. Should the test run pkg-config --version and try to parse the output? Or just ignore the test failure on very old distros?

@sillyousu This test failure is harmless and your Go is otherwise fine; feel free to ignore it and use the resulting go. You simply won't be able to link pkg-config libraries that are in paths containing whitespace (unlikely on CentOS).

@quentinmit Does the test work if you quote "-DDEFINED_FROM_PKG_CONFIG=hello world" on the Cflags line in the pc file? If that is more reliable with older versions of pkg-config, then that seems fine. We're checking our handling of pkg-config's output, not pkg-config's input parser.

Neither double quotes nor backslashes work in pkg-config 0.23. AFAICT there is simply no way to get whitespace into an argument in pkg-config 0.23.

Double quotes also don't work in OpenBSD's pkg-config, which is why I put backslashes into the test.

How about running something like pkg-config --version and t.Skip for older versions?

That's what I suggested above. Yeah, we can do that. I'm not sure what the best way to compare the version number is - parse with a regex?

@sillyousu Can you confirm what pkg-config --version prints for you? I'm expecting "0.23".

CL https://golang.org/cl/33027 mentions this issue.

@sillyousu Can you confirm what pkg-config --version prints for you? I'm expecting "0.23".

centos65x64TopHighoocwbezz➜ ~ pkg-config --version
0.23

@sillyousu This test failure is harmless and your Go is otherwise fine; feel free to ignore it and use the resulting go. You simply won't be able to link pkg-config libraries that are in paths containing whitespace (unlikely on CentOS).

The lack of pkg-config functionality doesn't bother me.
This failure stopping the subsequent test cases is a little bit annoying.