debug/elf: make safe for Go 1.4 compilers

We're going to start building cmd/cgo as part of the bootstrap,
and with it debug/elf, so the copy here needs to work with Go 1.4.
It does except for the use of the new io.SeekStart etc constants,
so remove that use.

Change-Id: Ib7fcf46e1e9060f96d2bacaaf349c9b0df347550
Reviewed-on: https://go-review.googlesource.com/68337
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

diff --git a/src/debug/elf/file.go b/src/debug/elf/file.go
index 8eeab65df89054aa0494e281683b22d244d15b00..95c0606f8022ee33b39a59a78e185d025a613abb 100644 (file)
--- a/src/debug/elf/file.go
+++ b/src/debug/elf/file.go
@@ -17,6 +17,17 @@ import (
        "strings"
 )
 
+// seekStart, seekCurrent, seekEnd are copies of
+// io.SeekStart, io.SeekCurrent, and io.SeekEnd.
+// We can't use the ones from package io because
+// we want this code to build with Go 1.4 during
+// cmd/dist bootstrap.
+const (
+       seekStart   int = 0
+       seekCurrent int = 1
+       seekEnd     int = 2
+)
+
 // TODO: error reporting detail
 
 /*
@@ -269,7 +280,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
        switch f.Class {
        case ELFCLASS32:
                hdr := new(Header32)
-               sr.Seek(0, io.SeekStart)
+               sr.Seek(0, seekStart)
                if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
                        return nil, err
                }
@@ -288,7 +299,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
                shstrndx = int(hdr.Shstrndx)
        case ELFCLASS64:
                hdr := new(Header64)
-               sr.Seek(0, io.SeekStart)
+               sr.Seek(0, seekStart)
                if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
                        return nil, err
                }
@@ -315,7 +326,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
        f.Progs = make([]*Prog, phnum)
        for i := 0; i < phnum; i++ {
                off := phoff + int64(i)*int64(phentsize)
-               sr.Seek(off, io.SeekStart)
+               sr.Seek(off, seekStart)
                p := new(Prog)
                switch f.Class {
                case ELFCLASS32:
@@ -359,7 +370,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
        names := make([]uint32, shnum)
        for i := 0; i < shnum; i++ {
                off := shoff + int64(i)*int64(shentsize)
-               sr.Seek(off, io.SeekStart)
+               sr.Seek(off, seekStart)
                s := new(Section)
                switch f.Class {
                case ELFCLASS32:

diff --git a/src/debug/elf/reader.go b/src/debug/elf/reader.go
index eab437318d6d3e3ee6513884df7120551ff6dae8..a45843619e5481bb08e0874c51640fca214b4d19 100644 (file)
--- a/src/debug/elf/reader.go
+++ b/src/debug/elf/reader.go
@@ -63,11 +63,11 @@ func (r *readSeekerFromReader) Read(p []byte) (n int, err error) {
 func (r *readSeekerFromReader) Seek(offset int64, whence int) (int64, error) {
        var newOffset int64
        switch whence {
-       case io.SeekStart:
+       case seekStart:
                newOffset = offset
-       case io.SeekCurrent:
+       case seekCurrent:
                newOffset = r.offset + offset
-       case io.SeekEnd:
+       case seekEnd:
                newOffset = r.size + offset
        default:
                return 0, os.ErrInvalid