golang/go · error

parameter may not start with quote character %c

Error message

parameter may not start with quote character %c

What it means

The pattern portion of a per-package flag value starts with a single quote (') or double quote (") character. The parser rejects this because shell quoting and the toolchain's own quoted.Split parser handle quote characters — a quote at the start of the pattern indicates malformed input where shell-level quoting bled into the value.

Source

Thrown at src/cmd/go/internal/load/flag.go:64

	match := func(_ *modload.Loader, p *Package) bool { return p.Internal.CmdlinePkg || p.Internal.CmdlineFiles } // default predicate with no pattern
	// For backwards compatibility with earlier flag splitting, ignore spaces around flags.
	v = strings.TrimSpace(v)
	if v == "" {
		// Special case: -gcflags="" means no flags for command-line arguments
		// (overrides previous -gcflags="-whatever").
		f.values = append(f.values, ppfValue{match, []string{}})
		return nil
	}
	if !strings.HasPrefix(v, "-") {
		i := strings.Index(v, "=")
		if i < 0 {
			return fmt.Errorf("missing =<value> in <pattern>=<value>")
		}
		if i == 0 {
			return fmt.Errorf("missing <pattern> in <pattern>=<value>")
		}
		if v[0] == '\'' || v[0] == '"' {
			return fmt.Errorf("parameter may not start with quote character %c", v[0])
		}
		pattern := strings.TrimSpace(v[:i])
		match = MatchPackage(pattern, cwd)
		v = v[i+1:]
	}
	flags, err := quoted.Split(v)
	if err != nil {
		return err
	}
	if flags == nil {
		flags = []string{}
	}
	f.values = append(f.values, ppfValue{match, flags})
	return nil
}

func (f *PerPackageFlag) String() string { return f.raw }

View on GitHub (pinned to b6b368adc5)

Solutions

1. Remove the leading quote character from the pattern portion of the value.
2. Keep shell quoting only at the outer level: go build -gcflags="./...=-N -l".
3. Use single quotes for the outer shell value if the inner value contains double quotes.

Example fix

// before — pattern starts with a quote character
go build -gcflags='"./...=-N -l"'
// after — no quote on the pattern
go build -gcflags="./...=-N -l"

// Check that the pattern portion does not start with a quote.
func validatePerPackageFlag(v string) error {
    v = strings.TrimSpace(v)
    if v == "" || strings.HasPrefix(v, "-") {
        return nil
    }
    if v[0] == '\'' || v[0] == '"' {
        return fmt.Errorf("pattern starts with quote: %q", v)
    }
    return nil
}

When it happens

Trigger: Passing -gcflags='"./..."=-N -l' where the pattern is wrapped in quotes inside the value string, or -ldflags='"mypkg"=-s -w'. The first byte of the trimmed value is ' or ".

Common situations: Over-quoting in shell commands — wrapping the pattern in quotes when the shell already quotes the entire value. Copy-pasting from documentation or examples that show quotes around patterns. Shell escaping issues with nested quotes.

Related errors

• missing =<value> in <pattern>=<value>
• missing <pattern> in <pattern>=<value>
• parse error
• reading %s: %v
• no Go source files

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/bfa5e9402e7758e8. Report an issue: GitHub.