err := ctxt.Out.Mmap(uint64(filesz))
	if err != nil {
		Exitf("mapping output file failed: %v", err)
	}
}

// relocSectFn wraps the function writing relocations of a section
// for parallel execution. Returns the wrapped function and a wait
// group for which the caller should wait.
func relocSectFn(ctxt *Link, relocSect func(*Link, *OutBuf, *sym.Section, []loader.Sym)) (func(*Link, *sym.Section, []loader.Sym), *sync.WaitGroup) {