cmd/go: env -changed misses CGO_LDFLAGS, others

[rliebz]

Go version

go version go1.23.2 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/rob/Library/Caches/go-build'
GOENV='/Users/rob/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/rob/.local/share/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/rob/.local/share/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.23.2/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.23.2/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.23.2'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/rob/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-w'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/ry/6bttgkt51f14fhb1cwsg_6r00000gp/T/go-build1178049255=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

Change the default value of CGO_LDFLAGS:

go env -w CGO_LDFLAGS=-w

Then check what values have changed:

go env -changed

What did you see happen?

No output

What did you expect to see?

I expected the output to be:

CGO_LDFLAGS='-w'

When most env variables are overridden in this way, they correctly show up in the output. Since CGO_LDFLAGS is one of the values that shows up in the output of go env without any flags, I would also expect it to be reflected with go env -changed when the value was non-default.

I have tested this with a few other cases and found inconsistent results, including:

• Some flags like CGO_ENABLED, GOPATH, GOPRIVATE, and CGO_CFLAGS are respected
• Other flags like CGO_LDFLAGS and GCCGO are not respected. It might literally be just these two, but I only tested a handful
• go env -changed does not seem to report a value if the corresponding environment variable is exported. To reproduce:

$ go env -w CGO_ENABLED=0
$ go env -changed
CGO_ENABLED='0'
$ CGO_ENABLED=0 go env -changed
$ CGO_ENABLED=2 go env -changed

I could not find anything in the original proposal (#34208) or in the docs (go help env) that would suggest why this would be the expected behavior.

[gabyhelp]

Related Issues and Documentation

• cmd/go: go env -changed prints changed values for variables in go.env #67542 (closed)
• cmd/go: setting the User or System Environment Variables #30190 (closed)
• runtime: cgo can't set new environment variables for Go #44108 (closed)
• cmd/go/internal/load: -ldflags should be included in buildinfo when -trimpath is set and CGO_ENABLED=0 #63558 (closed)
• cmd/go: document that empty environment variables are treated as unset #50335 (closed)
• cmd/go: print more env variables in "go env"
• cmd/go: add a way to query for non-defaults in the env #34208 (closed)
• cmd/go: GOMOD env var is not documented #26500 (closed)
• cmd/go: `go env` incorrect quoting for values with double quotes #58855 (closed)
• cmd/go: add $GOFLAGS environment variable

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[qiulaidongfeng]

Thanks report.
I will investigate.

[gopherbot]

Change https://go.dev/cl/621995 mentions this issue: cmd/go: fix incorrect determining default value of CGO_ENABLED

[gopherbot]

Change https://go.dev/cl/621996 mentions this issue: cmd/go: fix typo in ExtraEnvVarsCostly

[gopherbot]

Change https://go.dev/cl/621997 mentions this issue: cmd/go: fix GOCACHE error print non-default value when env set to default value

[qiulaidongfeng]

Thanks again for your report, I rechecked the implementation.
Three newly discovered bug have been sent CL fix.
old bug(#67492) fix in https://go.dev/cl/586241

[cagedmantis]

cc @matloob @samthanawalla

[gopherbot]

Change https://go.dev/cl/671635 mentions this issue: cmd/go: fix not print GCCGO when it's not the default