cmd/go: -trimpath with -mod=vendor doesn't trim path

[mark-rushakoff]

Given a single file main.go in a module:

package main

import "golang.org/x/text/search"

func main() {
	var p search.Pattern
	x, y := p.Index(nil, search.Backwards) // Deliberate panic here.
	println(x, y)
}

With go version go1.13.6 darwin/amd64, after running go mod vendor, then go run -mod=vendor -trimpath main.go returns the following output:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x10a9cbc]

goroutine 1 [running]:
golang.org/x/text/search.(*Pattern).Index(0xc000076f30, 0x0, 0x0, 0x0, 0xc000076f1f, 0x1, 0x1, 0xc000042750, 0xc000076f50)
	golang.org/x/[email protected]/search/search.go:177 +0x9c
main.main()
	example.com/trimpath@/main.go:7 +0x7f
exit status 2

Notice that the location is printed as golang.org/x/text@v0....

With go tip at go version devel +71154e061f Tue Jan 14 17:13:34 2020 +0000 darwin/amd64, running go run -mod=vendor -trimpath main.go produces this output:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x10ad40c]

goroutine 1 [running]:
golang.org/x/text/search.(*Pattern).Index(0xc000096f58, 0x0, 0x0, 0x0, 0xc000096f47, 0x1, 0x1, 0xc000044778, 0xc000096f78)
	/tmp/x/vendor/golang.org/x/text/search/search.go:177 +0x9c
main.main()
	example.com/trimpath@/main.go:7 +0x7e
exit status 2

Notice that now, the vendored module has changed to its absolute path on disk, /tmp/x/vendor/....

I bisected to 6cba4db as the commit which introduced this path-based output.

$ gotip version && gotip run -mod=vendor -trimpath main.go
go version devel +1736f3a126 Wed Oct 9 18:12:31 2019 +0000 darwin/amd64
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x10a4acc]

goroutine 1 [running]:
golang.org/x/text/search.(*Pattern).Index(0xc000076f30, 0x0, 0x0, 0x0, 0xc000076f1f, 0x1, 0x1, 0xc000042750, 0xc000076f50)
	golang.org/x/[email protected]/search/search.go:177 +0x9c
main.main()
	example.com/trimpath@/main.go:7 +0x7e
exit status 2

$ gotip version && gotip run -mod=vendor -trimpath main.go
go version devel +6cba4dbf80 Wed Oct 9 18:39:22 2019 +0000 darwin/amd64
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x10a4acc]

goroutine 1 [running]:
golang.org/x/text/search.(*Pattern).Index(0xc000076f30, 0x0, 0x0, 0x0, 0xc000076f1f, 0x1, 0x1, 0xc000042750, 0xc000076f50)
	/tmp/x/vendor/golang.org/x/text/search/search.go:177 +0x9c
main.main()
	example.com/trimpath@/main.go:7 +0x7e
exit status 2

With the new behavior since 6cba4db, -trimpath no longer works as documented in go help build ("remove all file system paths from the resulting executable").

/cc @bcmills @jayconrod

[ALTree]

Tentatively putting in the 1.14 milestone since if the bisection is correct this was introduced in this development cycle.

[jayconrod]

cc @bcmills @matloob

It looks like this is happening because we don't set the module root directory with -mod=vendor anymore. We're passing a -trimpath argument to the compiler like this:

-trimpath "$WORK/b002=>;=>golang.org/x/[email protected]" 

It should be:

-trimpath "$WORK/b002=>;/tmp/x/vendor/golang.org/x/text=>golang.org/x/[email protected]" 

This can also be seen with go list -f '{{.Module.Dir}}' golang.org/x/text/search.

[gopherbot]

Change https://golang.org/cl/214945 mentions this issue: cmd/go: trim paths from vendored packages with -trimpath

[cmitchell]

Is there any way this could be considered for a backport to the next go1.13 as well? I wouldn't be able to upgrade to 1.14 for sometime due to that version automatically switching over to TLS 1.3 and removing any switch to fallback to TLS1.2 but man have I hit this issue. I think this may have started with go1.13.5 honestly.

[jayconrod]

@cmitchell This issue was a regression introduced on the 1.14 development branch. I just confirmed it doesn't reproduce in 1.13.6.

Could you open a new issue with steps to reproduce the problem you're seeing?

[gopherbot]

Change https://golang.org/cl/215940 mentions this issue: cmd/go: unify trimpath logic for -mod=vendor, -mod=mod

[gopherbot]

Change https://golang.org/cl/216018 mentions this issue: cmd/go: add a control case to the mod_vendor_trimpath test