cmd/link: give the object reader its own package

For #22095

Change-Id: Ie9ae84c758af99ac7daed26d0b3e3b0a47599edd
Reviewed-on: https://go-review.googlesource.com/67315
Run-TryBot: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/buildtool.go

@@ -69,6 +69,7 @@ var bootstrapDirs = []string{
 	"cmd/link/internal/ld",
 	"cmd/link/internal/mips",
 	"cmd/link/internal/mips64",
+	"cmd/link/internal/objfile",
 	"cmd/link/internal/ppc64",
 	"cmd/link/internal/s390x",
 	"cmd/link/internal/sym",

src/cmd/link/internal/ld/lib.go

@@ -36,6 +36,7 @@ import (
 	"cmd/internal/bio"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
+	"cmd/link/internal/objfile"
 	"cmd/link/internal/sym"
 	"crypto/sha1"
 	"debug/elf"
@@ -359,7 +360,7 @@ func (ctxt *Link) loadlib() {
 			if ctxt.Debugvlog > 1 {
 				ctxt.Logf("%5.2f autolib: %s (from %s)\n", Cputime(), lib.File, lib.Objref)
 			}
-			objfile(ctxt, lib)
+			loadobjfile(ctxt, lib)
 		}
 	}
 
@@ -403,7 +404,7 @@ func (ctxt *Link) loadlib() {
 				if Buildmode == BuildmodeShared || *FlagLinkshared {
 					Exitf("cannot implicitly include runtime/cgo in a shared library")
 				}
-				objfile(ctxt, lib)
+				loadobjfile(ctxt, lib)
 			}
 		}
 	}
@@ -765,7 +766,7 @@ func genhash(ctxt *Link, lib *sym.Library) {
 	lib.Hash = hex.EncodeToString(h.Sum(nil))
 }
 
-func objfile(ctxt *Link, lib *sym.Library) {
+func loadobjfile(ctxt *Link, lib *sym.Library) {
 	pkg := objabi.PathToPrefix(lib.Pkg)
 
 	if ctxt.Debugvlog > 1 {
@@ -1459,7 +1460,7 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 	ldpkg(ctxt, f, pkg, import1-import0-2, pn, whence) // -2 for !\n
 	f.Seek(import1, 0)
 
-	LoadObjFile(ctxt.Arch, ctxt.Syms, f, lib, eof-f.Offset(), pn)
+	objfile.Load(ctxt.Arch, ctxt.Syms, f, lib, eof-f.Offset(), pn)
 	addImports(ctxt, lib, pn)
 	return nil
 }

src/cmd/link/internal/ld/objfile.go → src/cmd/link/internal/objfile/objfile.go

@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package ld
-
-// Reading of Go object files.
+// Package objfile reads Go object files for the Go linker, cmd/link.
+//
+// This package is similar to cmd/internal/objfile which also reads
+// Go object files.
+package objfile
 
 import (
 	"bufio"
@@ -51,7 +53,9 @@ type objReader struct {
 	file        []*sym.Symbol
 }
 
-func LoadObjFile(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, length int64, pn string) {
+// Load loads an object file f into library lib.
+// The symbols loaded are added to syms.
+func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, length int64, pn string) {
 	start := f.Offset()
 	r := &objReader{
 		rd:              f.Reader,
@@ -91,7 +95,7 @@ func (r *objReader) loadObjFile() {
 		r.lib.ImportStrings = append(r.lib.ImportStrings, lib)
 	}
 
-	// sym.Symbol references
+	// Symbol references
 	r.refs = []*sym.Symbol{nil} // zeroth ref is nil
 	for {
 		c, err := r.rd.Peek(1)