cmd/go: go tool doesn't pass command name as os.Args[0] when flags are present

[seankhliao]

Go version

go version devel go1.24-efe0a86551 2024-11-21 20:50:15 +0000 linux/amd64

Output of go env in your module/workspace:

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='0'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v3'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/user/.cache/go-build'
GODEBUG=''
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS='-trimpath "-ldflags=-s -w" -vet=all'
GOGCCFLAGS='-fPIC -m64 -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3521496734=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/user/tmp/testrepo0896/go.mod'
GOMODCACHE='/home/user/.data/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/user/.data/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/user/sdk/gotip'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/home/user/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='path'
GOTOOLDIR='/home/user/sdk/gotip/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.24-efe0a86551 2024-11-21 20:50:15 +0000'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

With a basic tool like: https://go.dev/play/p/0MpgRS3gwFS
Invoking it results in:

$ go tool mytool
[/home/user/.cache/go-build/05/05c95035c59ab02d5d47f8b72f30bf94aafdbe7a97a027a1a3ac48961b3a0fda-d/mytool]

$ go tool mytool -hello world
[-hello world]

What did you see happen?

The tool doesn't receive its own name in os.Args[0], messing up argument / flag parsing.

What did you expect to see?

the usual os.Args

[gabyhelp]

Related Issues

• cmd/go: breakage with go version command and GOFLAGS environment variable #41264 (closed)
• go build creates binary named "command-line-arguments" #34716 (closed)
• go tool compile #55111 (closed)
• flag: Args() should return the non-flag arguments regardless of their position relative to the flag arguments #24107 (closed)
• cmd/go: document the meaning of solitary "command-line-arguments" #36043
• cmd/go: flags ending with "=." is not correctly parsed by go tool when run via powershell #43179 (closed)
• cmd/go: specifying `-n` causes error with cgo #14944 (closed)
• os: commandLineToArgv() does not correctly parse argv[0] in Windows #50028
• cmd/go: `-toolexec` program inconsistently used for C toolchain #64580
• cmd/go: `go env` incorrect quoting for values with double quotes #58855 (closed)

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[seankhliao]

cc @matloob @samthanawalla @ConradIrwin

[gopherbot]

Change https://go.dev/cl/631075 mentions this issue: go/cmd: pass os.Args[0] to mod tools

[ConradIrwin]

Thanks for testing this out @seankhliao! - sent a fix, and please let me know if you run into anything else with this feature.