golang/go · error

%s entry cannot contain only space

Error message

%s entry cannot contain only space

What it means

Returned by checkEnvWrite for CC/CXX when quoted.Split succeeds but returns zero tokens (the value was only whitespace). An empty compiler is allowed (val == "" short-circuits earlier), but a whitespace-only value is rejected because it has no executable name.

Source

Thrown at src/cmd/go/internal/envcmd/env.go:686

			return fmt.Errorf("GOPATH entry cannot start with shell metacharacter '~': %q", val)
		}
		if !filepath.IsAbs(val) && val != "" {
			return fmt.Errorf("GOPATH entry is relative; must be absolute path: %q", val)
		}
	case "GOMODCACHE":
		if !filepath.IsAbs(val) && val != "" {
			return fmt.Errorf("GOMODCACHE entry is relative; must be absolute path: %q", val)
		}
	case "CC", "CXX":
		if val == "" {
			break
		}
		args, err := quoted.Split(val)
		if err != nil {
			return fmt.Errorf("invalid %s: %v", key, err)
		}
		if len(args) == 0 {
			return fmt.Errorf("%s entry cannot contain only space", key)
		}
		if !filepath.IsAbs(args[0]) && args[0] != filepath.Base(args[0]) {
			return fmt.Errorf("%s entry is relative; must be absolute path: %q", key, args[0])
		}
	}

	if !utf8.ValidString(val) {
		return fmt.Errorf("invalid UTF-8 in %s=... value", key)
	}
	if strings.Contains(val, "\x00") {
		return fmt.Errorf("invalid NUL in %s=... value", key)
	}
	if strings.ContainsAny(val, "\v\r\n") {
		return fmt.Errorf("invalid newline in %s=... value", key)
	}
	return nil
}

View on GitHub (pinned to b6b368adc5)

Solutions

1. If you want CGO disabled, set `CGO_ENABLED=0` instead of blanking CC.
2. Provide an actual compiler name: `go env -w CC=gcc`.
3. If you genuinely want the default, set CC to empty (val == "" is allowed): `go env -w CC=`.

Example fix

# before
$ go env -w CC="   "
error: CC entry cannot contain only space
# after — disable cgo properly
$ go env -w CGO_ENABLED=0

parts, err := quoted.Split(v)
if err != nil { return err }
if v != "" && len(parts) == 0 {
    return fmt.Errorf("CC/CXX value has no tokens")
}

When it happens

Trigger: `go env -w CC=" "`, `go env -w CXX="\t"`, or any CC/CXX value consisting solely of spaces/tabs.

Common situations: Config generators emitting placeholder whitespace; copy-paste that loses the compiler name but keeps surrounding spaces; scripts concatenating flags onto an empty CC.

Related errors

• invalid %s: %v
• %s entry is relative; must be absolute path: %q
• %s cannot be modified
• %s can only be set using the OS environment
• unknown go command variable %s

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/a8452c3dc5417742. Report an issue: GitHub.