golang/go · error

%s: can not find version number in %q

Error message

%s: can not find version number in %q

What it means

gccToolIDPrefix parsed the -### output line-by-line looking for a token 'version' immediately followed by a digit. If no line matches, the compiler's output format is unrecognized and the tool ID cannot be derived. The raw output is included in the error.

Source

Thrown at src/cmd/go/internal/work/buildid.go:278

				// Check that the next field is plausibly a version number.
				// We require only that it begins with an ASCII digit,
				// since we don't know what version numbering schemes a given
				// C compiler may use. (Clang and GCC mostly seem to follow the scheme X.Y.Z,
				// but in https://go.dev/issue/64619 we saw "8.3 [DragonFly]", and who knows
				// what other C compilers like "zig cc" might report?)
				next := fields[i+1]
				if len(next) > 0 && next[0] >= '0' && next[0] <= '9' {
					version = line
					break
				}
			}
		}
		if version != "" {
			break
		}
	}
	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)
		}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Use a mainstream gcc or gccgo release whose -### output is well-formed.
2. If using clang, ensure it's a complete install (not a stub).
3. File a bug / use a Go version with broader compiler-output parsing, or set -gcflags to bypass tool ID detection where supported.
4. Inspect the raw output quoted in the error to see what the compiler actually emits.

Example fix

// before
$ CC='zig cc' go build ./...
// error: zig: can not find version number in "..."

// after — use a standard gcc
$ CC=gcc go build ./...

// Check that a compiler emits a parseable 'version <digit>' line.
func checkCompilerVersionLine(name string) error {
    cmd := exec.Command(name, "-###", "-x", "c", "-c", "-")
    cmd.Env = append(os.Environ(), "LC_ALL=C")
    out, _ := cmd.CombinedOutput()
    re := regexp.MustCompile(`(?m)version\s+[0-9]`)
    if !re.Match(out) {
        return fmt.Errorf("%s emits no parseable version line; use a standard gcc/gccgo", name)
    }
    return nil
}

When it happens

Trigger: A C/gccgo compiler whose -### output doesn't include a 'version <digit...>' field — e.g. some clang builds, zig cc, tinycc, or a wrapper script that strips version info. Localized output is forced to C via LC_ALL=C, so localization isn't the cause.

Common situations: Using 'zig cc' or a musl-cross wrapper; a stripped/embedded clang; a custom gcc wrapper that filters -v output; an exotic vendor gcc.

Related errors

• %s: %v; output: %q
• %s: can not find compilation command 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/3a7b2e68a5d8af70. Report an issue: GitHub.