cmd/go: asmflags/gcflags trimpath ignored for standard library

[rittneje]

What version of Go are you using (go version)?

$ go version
go version go1.11.2 linux/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build591071936=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I recompiled the standard library with the intention of stripping out GOROOT from the paths.

go install -a -asmflags="all=-trimpath=$GOROOT/src" -gcflags="all=-trimpath=$GOROOT/src" std

I then built a sample binary (just a simple "hello world" program) against this new standard library, and ran strings on the resulting binary.

What did you expect to see?

I expected to see the trimmed version of all standard library paths (e.g., "fmt/print.go" instead of "/usr/local/go/src/fmt/print.go").

What did you see instead?

I see the untrimmed paths. This is a regression from 1.8, where doing the following results in a properly trimmed binary.

go install -a -asmflags="-trimpath=$GOROOT/src" -gcflags="-trimpath=$GOROOT/src" std

Curiously, this only appears to be an issue for the standard library. Trimming $GOPATH/src from my packages works as expected. I'm not sure where these strings are coming from, as everything in $GOROOT/pkg appears to be properly trimmed.

[bcmills]

Per #22382 (comment):

Users should not be using -trimpath. The general problem here is #16860.

As such, closing as a duplicate of #16860.