internal/core/mapping.go
func (m *Mapping) Source() (string, int64) {
	if m.f == nil {
		return "", 0
	}
	return m.f.Name(), m.off
}
func (m *Mapping) Source() (string, int64) {
	if m.f == nil {
		return "", 0
	}
	return m.f.Name(), m.off
}
// Source returns the backing file and offset for the mapping, or "", 0 if none.