What causes "symbol %s: invalid section number %d" in golang/go?

Use a fully-linked XCOFF executable so the symbol resolves to a real section.

symbol %s: invalid section number %d

Error message

symbol %s: invalid section number %d

What it means

findXCOFFSymbol locates a named symbol and then validates its SectionNumber. A SectionNumber <= 0 corresponds to special (undefined/absolute/debug) symbols that have no real section, which is unusable for the table-extraction caller that needs section-relative addressing. The lookup therefore fails for that symbol even though it exists by name.

Source

Thrown at src/cmd/internal/objfile/xcoff.go:116

}

func (f *xcoffFile) text() (textStart uint64, text []byte, err error) {
	sect := f.xcoff.Section(".text")
	if sect == nil {
		return 0, nil, fmt.Errorf("text section not found")
	}
	textStart = sect.VirtualAddress
	text, err = sect.Data()
	return
}

func findXCOFFSymbol(f *xcoff.File, name string) (*xcoff.Symbol, error) {
	for _, s := range f.Symbols {
		if s.Name != name {
			continue
		}
		if s.SectionNumber <= 0 {
			return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
		}
		if len(f.Sections) < s.SectionNumber {
			return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
		}
		return s, nil
	}
	return nil, fmt.Errorf("no %s symbol found", name)
}

func loadXCOFFTable(f *xcoff.File, sname, ename string) ([]byte, error) {
	ssym, err := findXCOFFSymbol(f, sname)
	if err != nil {
		return nil, err
	}
	esym, err := findXCOFFSymbol(f, ename)
	if err != nil {
		return nil, err
	}

View on GitHub (pinned to b6b368adc5)

Solutions

Use a fully-linked XCOFF executable so the symbol resolves to a real section.
Pick a symbol that is defined in a concrete section rather than an external reference.

Defensive patterns

Strategy: validation

Validate before calling

// Pre-filter candidates: only symbols with SectionNumber > 0 are usable.
// for _, s := range f.Symbols {
//     if s.Name == name && s.SectionNumber > 0 && int(s.SectionNumber) <= len(f.Sections) {
//         return s, nil
//     }
// }

Try / catch

// s, err := findXCOFFSymbol(f, name)
// if err != nil {
//     // 'invalid section number' -> symbol is undefined/absolute; use a linked binary
//     return nil, err
// }

Prevention

Use fully-linked XCOFF executables so symbols resolve to real sections.
Avoid looking up symbols that may remain undefined externals.
Rebuild if the requested symbol is unexpectedly undefined.

When it happens

Trigger: Looking up a symbol that exists in the XCOFF symbol table but whose SectionNumber is <= 0 (e.g. an undefined external reference or an absolute symbol).

Common situations: A binary where the requested symbol (e.g. runtime.pclntab) is still undefined because the object was not fully linked, or a symbol defined as absolute/debug.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/85d075f51188a44c. Report an issue: GitHub.