golang/go · error

%s: compilation command confusion %q

Error message

%s: compilation command confusion %q

What it means

gccToolIDPrefix found the indented compiler-command line in experimental -### output, but quoted.Split on that line yielded zero fields. This means the line consists only of whitespace/quotes that the splitter couldn't tokenize — an invariant violation in the compiler's output format.

Source

Thrown at src/cmd/go/internal/work/buildid.go:300

		// 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.
		if id == "" {
			id = b.fileHash(exe)
		}
	}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Capture the raw -### output and inspect the indented line that should hold the command.
2. Use a release gcc/gccgo rather than a patched/experimental one.
3. Report the malformed output to the Go issue tracker.
4. Temporarily set -compiler=gc if gccgo isn't required.

Example fix

// before
$ GCCGO=/opt/gccgo-patched/bin/gccgo go build -compiler=gccgo ./...
// error: /opt/gccgo-patched/bin/gccgo: compilation command confusion "..."

// after
$ GCCGO=gccgo go build -compiler=gccgo ./...
# or diagnose: /opt/gccgo-patched/bin/gccgo -### -x go -c -

When it happens

Trigger: An experimental gcc/gccgo whose expanded command line is empty or malformed (e.g. just a stray quote or whitespace). Extremely rare; indicates a broken or non-standard compiler driver.

Common situations: A patched gcc that emits an empty expanded command; a wrapper that strips all tokens but leaves the line prefix; concurrent truncation of the captured output.

Related errors

• %s: %v; output: %q
• %s: can not find version number in %q
• %s: can not find compilation command in %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/6c8dbb9ce93ad13d. Report an issue: GitHub.