cmd/link/internal/ld: reduce the scope of some local declarations

Move some local declarations closer to their use, reducing their
respective lifetimes. Spotted while reviewing CL 67318.

Change-Id: I68db67fe8530344d95e50efb6587bc724e1171f5
Reviewed-on: https://go-review.googlesource.com/67370
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -381,20 +381,11 @@ func trampoline(ctxt *Link, s *Symbol) {
 
 // resolve relocations in s.
 func relocsym(ctxt *Link, s *Symbol) {
-	var r *Reloc
-	var rs *Symbol
-	var i16 int16
-	var off int32
-	var siz int32
-	var fl int32
-	var o int64
-
 	for ri := int32(0); ri < int32(len(s.R)); ri++ {
-		r = &s.R[ri]
-
+		r := &s.R[ri]
 		r.Done = true
-		off = r.Off
-		siz = int32(r.Siz)
+		off := r.Off
+		siz := int32(r.Siz)
 		if off < 0 || off+siz > int32(len(s.P)) {
 			rname := ""
 			if r.Sym != nil {
@@ -450,6 +441,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 			}
 		}
 
+		var o int64
 		switch r.Type {
 		default:
 			switch siz {
@@ -535,7 +527,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 				r.Done = false
 
 				// set up addend for eventual relocation via outer symbol.
-				rs = r.Sym
+				rs := r.Sym
 
 				r.Xadd = r.Add
 				for rs.Outer != nil {
@@ -607,7 +599,6 @@ func relocsym(ctxt *Link, s *Symbol) {
 				r.Xadd = r.Add + Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr)
 
 				o = r.Xadd
-				rs = r.Xsym
 				if Iself && SysArch.Family == sys.AMD64 {
 					o = 0
 				}
@@ -647,7 +638,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 				r.Done = false
 
 				// set up addend for eventual relocation via outer symbol.
-				rs = r.Sym
+				rs := r.Sym
 
 				r.Xadd = r.Add
 				for rs.Outer != nil {
@@ -722,7 +713,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 			if o != int64(int16(o)) {
 				Errorf(s, "relocation address for %s is too big: %#x", r.Sym.Name, o)
 			}
-			i16 = int16(o)
+			i16 := int16(o)
 			ctxt.Arch.ByteOrder.PutUint16(s.P[off:], uint16(i16))
 		case 4:
 			if r.Type == objabi.R_PCREL || r.Type == objabi.R_CALL {
@@ -735,7 +726,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 				}
 			}
 
-			fl = int32(o)
+			fl := int32(o)
 			ctxt.Arch.ByteOrder.PutUint32(s.P[off:], uint32(fl))
 		case 8:
 			ctxt.Arch.ByteOrder.PutUint64(s.P[off:], uint64(o))
@@ -2233,12 +2224,11 @@ func (ctxt *Link) address() {
 	var noptr *Section
 	var bss *Section
 	var noptrbss *Section
-	var vlen int64
 	for i, s := range Segdata.Sections {
 		if Iself && s.Name == ".tbss" {
 			continue
 		}
-		vlen = int64(s.Length)
+		vlen := int64(s.Length)
 		if i+1 < len(Segdata.Sections) && !(Iself && Segdata.Sections[i+1].Name == ".tbss") {
 			vlen = int64(Segdata.Sections[i+1].Vaddr - s.Vaddr)
 		}
@@ -2270,7 +2260,7 @@ func (ctxt *Link) address() {
 		Segdwarf.Fileoff = Segdata.Fileoff + uint64(Rnd(int64(Segdata.Filelen), int64(PEFILEALIGN)))
 	}
 	for i, s := range Segdwarf.Sections {
-		vlen = int64(s.Length)
+		vlen := int64(s.Length)
 		if i+1 < len(Segdwarf.Sections) {
 			vlen = int64(Segdwarf.Sections[i+1].Vaddr - s.Vaddr)
 		}

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

@@ -1462,7 +1462,6 @@ func elfdynhash(ctxt *Link) {
 	chain := make([]uint32, nsym)
 	buckets := make([]uint32, nbucket)
 
-	var b int
 	for _, sy := range ctxt.Syms.Allsym {
 		if sy.Dynid <= 0 {
 			continue
@@ -1475,7 +1474,7 @@ func elfdynhash(ctxt *Link) {
 		name := sy.Extname
 		hc := elfhash(name)
 
-		b = int(hc % uint32(nbucket))
+		b := hc % uint32(nbucket)
 		chain[sy.Dynid] = buckets[b]
 		buckets[b] = uint32(sy.Dynid)
 	}
@@ -1507,15 +1506,13 @@ func elfdynhash(ctxt *Link) {
 	s = ctxt.Syms.Lookup(".gnu.version_r", 0)
 	i = 2
 	nfile := 0
-	var j int
-	var x *Elfaux
 	for l := needlib; l != nil; l = l.next {
 		nfile++
 
 		// header
 		Adduint16(ctxt, s, 1) // table version
-		j = 0
-		for x = l.aux; x != nil; x = x.next {
+		j := 0
+		for x := l.aux; x != nil; x = x.next {
 			j++
 		}
 		Adduint16(ctxt, s, uint16(j))                         // aux count
@@ -1527,7 +1524,7 @@ func elfdynhash(ctxt *Link) {
 			Adduint32(ctxt, s, 0)
 		}
 
-		for x = l.aux; x != nil; x = x.next {
+		for x := l.aux; x != nil; x = x.next {
 			x.num = i
 			i++
 
@@ -1613,24 +1610,18 @@ func elfphrelro(seg *Segment) {
 }
 
 func elfshname(name string) *ElfShdr {
-	var off int
-	var sh *ElfShdr
-
 	for i := 0; i < nelfstr; i++ {
 		if name == elfstr[i].s {
-			off = elfstr[i].off
+			off := elfstr[i].off
 			for i = 0; i < int(ehdr.shnum); i++ {
-				sh = shdr[i]
+				sh := shdr[i]
 				if sh.name == uint32(off) {
 					return sh
 				}
 			}
-
-			sh = newElfShdr(int64(off))
-			return sh
+			return newElfShdr(int64(off))
 		}
 	}
-
 	Exitf("cannot find elf name %s", name)
 	return nil
 }
@@ -1638,14 +1629,10 @@ func elfshname(name string) *ElfShdr {
 // Create an ElfShdr for the section with name.
 // Create a duplicate if one already exists with that name
 func elfshnamedup(name string) *ElfShdr {
-	var off int
-	var sh *ElfShdr
-
 	for i := 0; i < nelfstr; i++ {
 		if name == elfstr[i].s {
-			off = elfstr[i].off
-			sh = newElfShdr(int64(off))
-			return sh
+			off := elfstr[i].off
+			return newElfShdr(int64(off))
 		}
 	}
 

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

@@ -29,8 +29,6 @@ func expandpkg(t0 string, pkg string) string {
 //		libmach, so that other linkers and ar can share.
 
 func ldpkg(ctxt *Link, f *bio.Reader, pkg string, length int64, filename string, whence int) {
-	var p0, p1 int
-
 	if *flagG {
 		return
 	}
@@ -95,7 +93,8 @@ func ldpkg(ctxt *Link, f *bio.Reader, pkg string, length int64, filename string,
 	}
 
 	// look for cgo section
-	p0 = strings.Index(data, "\n$$  // cgo")
+	p0 := strings.Index(data, "\n$$  // cgo")
+	var p1 int
 	if p0 >= 0 {
 		p0 += p1
 		i := strings.IndexByte(data[p0+1:], '\n')
@@ -128,9 +127,6 @@ func ldpkg(ctxt *Link, f *bio.Reader, pkg string, length int64, filename string,
 func loadcgo(ctxt *Link, file string, pkg string, p string) {
 	var next string
 	var q string
-	var f []string
-	var local string
-	var remote string
 	var lib string
 	var s *Symbol
 
@@ -143,7 +139,7 @@ func loadcgo(ctxt *Link, file string, pkg string, p string) {
 		}
 
 		p0 = p // save for error message
-		f = tokenize(p)
+		f := tokenize(p)
 		if len(f) == 0 {
 			continue
 		}
@@ -153,8 +149,8 @@ func loadcgo(ctxt *Link, file string, pkg string, p string) {
 				goto err
 			}
 
-			local = f[1]
-			remote = local
+			local := f[1]
+			remote := local
 			if len(f) > 2 {
 				remote = f[2]
 			}
@@ -205,7 +201,7 @@ func loadcgo(ctxt *Link, file string, pkg string, p string) {
 			if len(f) != 2 {
 				goto err
 			}
-			local = f[1]
+			local := f[1]
 			s = ctxt.Syms.Lookup(local, 0)
 			s.Type = SHOSTOBJ
 			s.Size = 0
@@ -216,7 +212,8 @@ func loadcgo(ctxt *Link, file string, pkg string, p string) {
 			if len(f) < 2 || len(f) > 3 {
 				goto err
 			}
-			local = f[1]
+			local := f[1]
+			var remote string
 			if len(f) > 2 {
 				remote = f[2]
 			} else {

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

@@ -450,36 +450,18 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 	localSymVersion := ctxt.Syms.IncVersion()
 	base := f.Offset()
 
-	var add uint64
-	var e binary.ByteOrder
-	var elfobj *ElfObj
-	var flag int
-	var hdr *ElfHdrBytes
 	var hdrbuf [64]uint8
-	var info uint64
-	var is64 int
-	var j int
-	var n int
-	var name string
-	var p []byte
-	var r []Reloc
-	var rela int
-	var rp *Reloc
-	var rsect *ElfSect
-	var s *Symbol
-	var sect *ElfSect
-	var sym ElfSym
-	var symbols []*Symbol
 	if _, err := io.ReadFull(f, hdrbuf[:]); err != nil {
 		Errorf(nil, "%s: malformed elf file: %v", pn, err)
 		return
 	}
-	hdr = new(ElfHdrBytes)
+	hdr := new(ElfHdrBytes)
 	binary.Read(bytes.NewReader(hdrbuf[:]), binary.BigEndian, hdr) // only byte arrays; byte order doesn't matter
 	if string(hdr.Ident[:4]) != "\x7FELF" {
 		Errorf(nil, "%s: malformed elf file", pn)
 		return
 	}
+	var e binary.ByteOrder
 	switch hdr.Ident[5] {
 	case ElfDataLsb:
 		e = binary.LittleEndian
@@ -493,7 +475,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 	}
 
 	// read header
-	elfobj = new(ElfObj)
+	elfobj := new(ElfObj)
 
 	elfobj.e = e
 	elfobj.f = f
@@ -501,7 +483,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 	elfobj.length = length
 	elfobj.name = pn
 
-	is64 = 0
+	is64 := 0
 	if hdr.Ident[4] == ElfClass64 {
 		is64 = 1
 		hdr := new(ElfHdrBytes64)
@@ -609,7 +591,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			Errorf(nil, "%s: malformed elf file", pn)
 			return
 		}
-		sect = &elfobj.sect[i]
+		sect := &elfobj.sect[i]
 		if is64 != 0 {
 			var b ElfSectBytes64
 
@@ -655,7 +637,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 		return
 	}
 
-	sect = &elfobj.sect[elfobj.shstrndx]
+	sect := &elfobj.sect[elfobj.shstrndx]
 	if err := elfmap(elfobj, sect); err != nil {
 		Errorf(nil, "%s: malformed elf file: %v", pn, err)
 		return
@@ -720,8 +702,8 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			}
 		}
 
-		name = fmt.Sprintf("%s(%s)", pkg, sect.name)
-		s = ctxt.Syms.Lookup(name, localSymVersion)
+		name := fmt.Sprintf("%s(%s)", pkg, sect.name)
+		s := ctxt.Syms.Lookup(name, localSymVersion)
 
 		switch int(sect.flags) & (ElfSectFlagAlloc | ElfSectFlagWrite | ElfSectFlagExec) {
 		default:
@@ -757,9 +739,10 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 
 	// enter sub-symbols into symbol table.
 	// symbol 0 is the null symbol.
-	symbols = make([]*Symbol, elfobj.nsymtab)
+	symbols := make([]*Symbol, elfobj.nsymtab)
 
 	for i := 1; i < elfobj.nsymtab; i++ {
+		var sym ElfSym
 		if err := readelfsym(ctxt, elfobj, i, &sym, 1, localSymVersion); err != nil {
 			Errorf(nil, "%s: malformed elf file: %v", pn, err)
 			return
@@ -769,7 +752,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			continue
 		}
 		if sym.shndx == ElfSymShnCommon || sym.type_ == ElfSymTypeCommon {
-			s = sym.sym
+			s := sym.sym
 			if uint64(s.Size) < sym.size {
 				s.Size = int64(sym.size)
 			}
@@ -806,7 +789,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			continue
 		}
 
-		s = sym.sym
+		s := sym.sym
 		if s.Outer != nil {
 			if s.Attr.DuplicateOK() {
 				continue
@@ -831,7 +814,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 		}
 
 		if elfobj.machine == ElfMachPower64 {
-			flag = int(sym.other) >> 5
+			flag := int(sym.other) >> 5
 			if 2 <= flag && flag <= 6 {
 				s.Localentry = 1 << uint(flag-2)
 			} else if flag == 7 {
@@ -842,8 +825,8 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 
 	// Sort outer lists by address, adding to textp.
 	// This keeps textp in increasing address order.
-	for i := 0; uint(i) < elfobj.nsect; i++ {
-		s = elfobj.sect[i].sym
+	for i := uint(0); i < elfobj.nsect; i++ {
+		s := elfobj.sect[i].sym
 		if s == nil {
 			continue
 		}
@@ -867,8 +850,8 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 	}
 
 	// load relocations
-	for i := 0; uint(i) < elfobj.nsect; i++ {
-		rsect = &elfobj.sect[i]
+	for i := uint(0); i < elfobj.nsect; i++ {
+		rsect := &elfobj.sect[i]
 		if rsect.type_ != ElfSectRela && rsect.type_ != ElfSectRel {
 			continue
 		}
@@ -880,16 +863,17 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			Errorf(nil, "%s: malformed elf file: %v", pn, err)
 			return
 		}
-		rela = 0
+		rela := 0
 		if rsect.type_ == ElfSectRela {
 			rela = 1
 		}
-		n = int(rsect.size / uint64(4+4*is64) / uint64(2+rela))
-		r = make([]Reloc, n)
-		p = rsect.base
-		for j = 0; j < n; j++ {
-			add = 0
-			rp = &r[j]
+		n := int(rsect.size / uint64(4+4*is64) / uint64(2+rela))
+		r := make([]Reloc, n)
+		p := rsect.base
+		for j := 0; j < n; j++ {
+			var add uint64
+			rp := &r[j]
+			var info uint64
 			if is64 != 0 {
 				// 64-bit rel/rela
 				rp.Off = int32(e.Uint64(p))
@@ -924,6 +908,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 			if info>>32 == 0 { // absolute relocation, don't bother reading the null symbol
 				rp.Sym = nil
 			} else {
+				var sym ElfSym
 				if err := readelfsym(ctxt, elfobj, int(info>>32), &sym, 0, 0); err != nil {
 					Errorf(nil, "%s: malformed elf file: %v", pn, err)
 					return
@@ -964,7 +949,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
 		sort.Sort(rbyoff(r[:n]))
 		// just in case
 
-		s = sect.sym
+		s := sect.sym
 		s.R = r
 		s.R = s.R[:n]
 	}

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

@@ -306,12 +306,9 @@ func macholoadrel(m *ldMachoObj, sect *ldMachoSect) int {
 	if _, err := io.ReadFull(m.f, buf); err != nil {
 		return -1
 	}
-	var p []byte
-	var r *ldMachoRel
-	var v uint32
-	for i := 0; uint32(i) < sect.nreloc; i++ {
-		r = &rel[i]
-		p = buf[i*8:]
+	for i := uint32(0); i < sect.nreloc; i++ {
+		r := &rel[i]
+		p := buf[i*8:]
 		r.addr = m.e.Uint32(p)
 
 		// TODO(rsc): Wrong interpretation for big-endian bitfields?
@@ -319,7 +316,7 @@ func macholoadrel(m *ldMachoObj, sect *ldMachoSect) int {
 			// scatterbrained relocation
 			r.scattered = 1
 
-			v = r.addr >> 24
+			v := r.addr >> 24
 			r.addr &= 0xFFFFFF
 			r.type_ = uint8(v & 0xF)
 			v >>= 4
@@ -328,7 +325,7 @@ func macholoadrel(m *ldMachoObj, sect *ldMachoSect) int {
 			r.pcrel = uint8(v & 1)
 			r.value = m.e.Uint32(p[4:])
 		} else {
-			v = m.e.Uint32(p[4:])
+			v := m.e.Uint32(p[4:])
 			r.symnum = v & 0xFFFFFF
 			v >>= 24
 			r.pcrel = uint8(v & 1)
@@ -390,11 +387,9 @@ func macholoadsym(m *ldMachoObj, symtab *ldMachoSymtab) int {
 	}
 	sym := make([]ldMachoSym, symtab.nsym)
 	p := symbuf
-	var s *ldMachoSym
-	var v uint32
-	for i := 0; uint32(i) < symtab.nsym; i++ {
-		s = &sym[i]
-		v = m.e.Uint32(p)
+	for i := uint32(0); i < symtab.nsym; i++ {
+		s := &sym[i]
+		v := m.e.Uint32(p)
 		if v >= symtab.strsize {
 			return -1
 		}

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

@@ -273,11 +273,8 @@ func machowrite() int {
 		Thearch.Lput(0) /* reserved */
 	}
 
-	var j int
-	var s *MachoSeg
-	var t *MachoSect
 	for i := 0; i < nseg; i++ {
-		s = &seg[i]
+		s := &seg[i]
 		if macho64 {
 			Thearch.Lput(LC_SEGMENT_64)
 			Thearch.Lput(72 + 80*s.nsect)
@@ -304,8 +301,8 @@ func machowrite() int {
 			Thearch.Lput(s.flag)
 		}
 
-		for j = 0; uint32(j) < s.nsect; j++ {
-			t = &s.sect[j]
+		for j := uint32(0); j < s.nsect; j++ {
+			t := &s.sect[j]
 			if macho64 {
 				strnput(t.name, 16)
 				strnput(t.segname, 16)
@@ -335,12 +332,11 @@ func machowrite() int {
 		}
 	}
 
-	var l *MachoLoad
 	for i := 0; i < len(load); i++ {
-		l = &load[i]
+		l := &load[i]
 		Thearch.Lput(l.type_)
 		Thearch.Lput(4 * (uint32(len(l.data)) + 2))
-		for j = 0; j < len(l.data); j++ {
+		for j := 0; j < len(l.data); j++ {
 			Thearch.Lput(l.data[j])
 		}
 	}