go/build: sourcehut requires characters considered unsafe for cgo names

[ddevault]

build.go has a set of safe characters which can be present in CFLAGS:

go/src/go/build/build.go

Lines 1553 to 1559 in c290cb6

	// NOTE: $ is not safe for the shell, but it is allowed here because of linker options like -Wl,$ORIGIN.
	// We never pass these arguments to a shell (just to programs we construct argv for), so this should be okay.
	// See golang.org/issue/6038.
	// The @ is for OS X. See golang.org/issue/13720.
	// The % is for Jenkins. See golang.org/issue/16959.
	// The ! is because module paths may use them. See golang.org/issue/26716.
	const safeString = "+-.,/0123456789=ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz:$@%! "

Sourcehut packages always have ~ in the URL, and in the future will likely have ^ as well. Importing a package from sr.ht which uses ${SRCDIR} in its CFLAGS accordingly causes this error:

widgets/terminal.go:11:2: /home/sircmpwn/.local/share/go/pkg/mod/git.sr.ht/~sircmpwn/go-libvterm@v0.0.0-20190526184212-d093d527d591/vterm.go: malformed #cgo argument: -I/home/sircmpwn/.local/share/go/pkg/mod/git.sr.ht/~sircmpwn/go-libvterm@v0.0.0-20190526184212-d093d527d591/libvterm/include/

~ has a special meaning in the shell, but it is URL safe and, per the comments in build.go, this string is never expanded with a shell.

EDIT: added permalink

[AlexRouSg]

ping @ianlancetaylor

[ddevault]

Bump? This should be easy to fix, is definitely a bug in golang, and shows unfair favoritism towards other platforms.

[ianlancetaylor]

Want to send in a patch?

[ddevault]

I don't really want to sign the CLA to be honest :/ I've pointed out the line of code which needs updating and it should be a one-line change, nay, a one-character change.

[gopherbot]

Change https://golang.org/cl/199918 mentions this issue: go/build: add ~ and ^ to safe character whitelist

[mvdan]

Please note that these changes often aren't a trivial one-line fix. At minimum, it should include a small regression test. And the author should ensure that no other features or tests break because of the change.