golang/go · error

%s: can not find compilation command in %q

Error message

%s: can not find compilation command in %q

What it means

For development ('experimental') builds of gcc/gccgo, gccToolIDPrefix expects the first line starting with a space (and not ' (in-process)') to be the expanded compiler invocation. If no such line exists, the version was marked experimental but the compiler subcommand couldn't be located.

Source

Thrown at src/cmd/go/internal/work/buildid.go:295

	if version == "" {
		return "", "", fmt.Errorf("%s: can not find version number in %q", name, out)
	}

	if !strings.Contains(version, "experimental") {
		// This is a release. Use this line as the tool ID.
		id = version
	} else {
		// This is a development version. The first line with
		// a leading space is the compiler proper.
		compiler := ""
		for _, line := range lines {
			if strings.HasPrefix(line, " ") && !strings.HasPrefix(line, " (in-process)") {
				compiler = line
				break
			}
		}
		if compiler == "" {
			return "", "", fmt.Errorf("%s: can not find compilation command in %q", name, out)
		}

		fields, _ := quoted.Split(compiler)
		if len(fields) == 0 {
			return "", "", fmt.Errorf("%s: compilation command confusion %q", name, out)
		}
		exe = fields[0]
		if !strings.ContainsAny(exe, `/\`) {
			if lp, err := pathcache.LookPath(exe); err == nil {
				exe = lp
			}
		}
		id, err = buildid.ReadFile(exe)
		if err != nil {
			return "", "", err
		}

		// If we can't find a build ID, use a hash.

View on GitHub (pinned to b6b368adc5)

Solutions

1. Run '<compiler> -### -x c -c -' manually and inspect the output format.
2. Switch to a stable release gcc/gccgo whose -### output is canonical.
3. Report the compiler version upstream or to the Go issue tracker with the captured output.
4. As a workaround, pin tool ID via GOFLAGS or use a release compiler for the build.

Example fix

// before — self-built gcc trunk
$ CC=/opt/gcc-trunk/bin/gcc go build ./...
// error: /opt/gcc-trunk/bin/gcc: can not find compilation command in "..."

// after — use release gcc
$ CC=gcc go build ./...
# or inspect: /opt/gcc-trunk/bin/gcc -### -x c -c -

When it happens

Trigger: A development snapshot of gcc/gccgo whose -### output omits the expanded cc1/cc1go subcommand line, or wraps it differently. The parser found 'experimental' in the version line but couldn't find the indented command line that follows.

Common situations: Building Go against a self-built gcc trunk; a distro's gcc snapshot package; a compiler wrapper that reformats -### output.

Related errors

• %s: %v; output: %q
• %s: can not find version number in %q
• %s: compilation command confusion %q
• C compiler %q not found: %v
• Fortran source files not allowed when not using cgo or SWIG:

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/a7a8a3ffa2154f76. Report an issue: GitHub.