cmd/ld: -X flag broken

[josharian]

$ cd test
$ ./run
fail: ./linkx.go


Or more directly:

$ cat x.go
package main

var s string

func main() {
    println(s)
}
$ go build -ldflags="-X main.s hi" x.go
 command-line-arguments
missing Go type information for global symbol: main.s size 16


See also issue #4139.

[josharian]

Comment 1:

Labels changed: added release-go1.4, repo-main.

[gopherbot]

Comment 2:

CL https://golang.org/cl/142680043 mentions this issue.

[gopherbot]

Comment 3:

CL https://golang.org/cl/144630044 mentions this issue.

[rsc]

Comment 4:

Owner changed to @rsc.

Status changed to Started.

[gopherbot]

Comment 5:

CL https://golang.org/cl/145420043 mentions this issue.

[rsc]

Comment 6:

This issue was closed by revision df781cc.

Status changed to Fixed.

[bgentry]

Comment 7:

I'm actually still seeing an issue here. Am I doing something wrong, or is this not
actually fixed?
➜  go build -ldflags="-X BuildTag TEST" x.go   
# command-line-arguments
missing Go type information for global symbol: BuildTag size 16
➜  go version
go version devel +5450f6b00f00 Fri Sep 26 13:50:53 2014 -0400 darwin/amd64
➜  cat x.go
package main
import "fmt"
var (
    BuildTag = "dev"
)
func main() {
    fmt.Println(BuildTag)
}

[bgentry]

Comment 8:

Ugh, spoke too soon. My flag should have been `-X main.BuildTag TEST`. Sorry about the
noise.

[josharian]

Comment 9:

Perhaps the linker should warn when the -X key doesn't match anything. Feel free to file
an issue for that if you'd like.

[bgentry]

Comment 10:

Ok, there is in fact still a bug here (or at least a change in behavior since 1.3). When
you specify an overwrite for a package your build doesn't actually use, there is a type
error. The same set of commands and files builds fine under 1.3, and also worked on tip
until earlier this week when the changes that broke the -X flag were committed.
➜  cat ~/go/src/github.com/bgentry/gotag/gotag.go 
package gotag
var (
    BuildTag = "dev"
)
➜  cat ~/go/src/github.com/bgentry/gotag/sub/sub.go
package main
import "fmt"
func main() {
    fmt.Println("hello")
}
==============
The behavior on 1.3.2:
➜  go version                                                   
go version go1.3.2 darwin/amd64
➜  go build -ldflags="-X github.com/bgentry/gotag.BuildTag TEST"
github.com/bgentry/gotag/sub
(no error)
==============
Now, on tip:
➜  go version
go version devel +5450f6b00f00 Fri Sep 26 13:50:53 2014 -0400 darwin/amd64
➜  go build -ldflags="-X github.com/bgentry/gotag.BuildTag TEST"
github.com/bgentry/gotag/sub
# github.com/bgentry/gotag/sub
missing Go type information for global symbol: github.com/bgentry/gotag.BuildTag size 16

[josharian]

Comment 11:

Thanks, Blake. I filed issue #8820 and issue #8821 for these. (The tests around linking
are in flux right now, so it'll may be easier to let that stabilize before fixing.)