[dev.link] cmd: convert symbol "shared" flag to object file flag

For the new object file format, don't tag individual symbols with a
"shared" flag, since that characteristic is better off as an attribute
of the containing object file as opposed to the individual symbol. Add
a new flags field in the object file header and put a bit in the flags
if the shared flags is in effect during compilation.

Change-Id: I2cf6d33bf7bf2fd8a7614ae0cd6ef03914777498
Reviewed-on: https://go-review.googlesource.com/c/go/+/201398
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

diff --git a/src/cmd/internal/goobj2/objfile.go b/src/cmd/internal/goobj2/objfile.go
index bc3a0072f1908f10fdad2511b53e67fa3064fdeb..ef32c4873ebf5e0d3cb275c09e73c22f02d4e66c 100644 (file)
--- a/src/cmd/internal/goobj2/objfile.go
+++ b/src/cmd/internal/goobj2/objfile.go
@@ -20,6 +20,7 @@ import (
 //
 //    Header struct {
 //       Magic   [...]byte   // "\x00go114LD"
+//       Flags   uint32
 //       // TODO: Fingerprint
 //       Offsets [...]uint32 // byte offset of each block below
 //    }
@@ -148,6 +149,7 @@ const (
 // TODO: probably no need to export this.
 type Header struct {
        Magic   string
+       Flags   uint32
        Offsets [NBlk]uint32
 }
 
@@ -155,6 +157,7 @@ const Magic = "\x00go114LD"
 
 func (h *Header) Write(w *Writer) {
        w.RawString(h.Magic)
+       w.Uint32(h.Flags)
        for _, x := range h.Offsets {
                w.Uint32(x)
        }
@@ -167,6 +170,8 @@ func (h *Header) Read(r *Reader) error {
                return errors.New("wrong magic, not a Go object file")
        }
        off := uint32(len(h.Magic))
+       h.Flags = r.uint32At(off)
+       off += 4
        for i := range h.Offsets {
                h.Offsets[i] = r.uint32At(off)
                off += 4
@@ -175,7 +180,7 @@ func (h *Header) Read(r *Reader) error {
 }
 
 func (h *Header) Size() int {
-       return len(h.Magic) + 4*len(h.Offsets)
+       return len(h.Magic) + 4 + 4*len(h.Offsets)
 }
 
 // Symbol definition.
@@ -189,6 +194,10 @@ type Sym struct {
 
 const SymABIstatic = ^uint16(0)
 
+const (
+       ObjFlagShared = 1 << iota
+)
+
 const (
        SymFlagDupok = 1 << iota
        SymFlagLocal
@@ -196,7 +205,6 @@ const (
        SymFlagLeaf
        SymFlagCFunc
        SymFlagReflectMethod
-       SymFlagShared // This is really silly
        SymFlagTopFrame
 )
 
@@ -226,7 +234,6 @@ func (s *Sym) Typelink() bool      { return s.Flag&SymFlagTypelink != 0 }
 func (s *Sym) Leaf() bool          { return s.Flag&SymFlagLeaf != 0 }
 func (s *Sym) CFunc() bool         { return s.Flag&SymFlagCFunc != 0 }
 func (s *Sym) ReflectMethod() bool { return s.Flag&SymFlagReflectMethod != 0 }
-func (s *Sym) Shared() bool        { return s.Flag&SymFlagShared != 0 }
 func (s *Sym) TopFrame() bool      { return s.Flag&SymFlagTopFrame != 0 }
 
 // Symbol reference.
@@ -596,3 +603,8 @@ func (r *Reader) PcdataBase() uint32 {
 func (r *Reader) ReadOnly() bool {
        return r.readonly
 }
+
+// Flags returns the flag bits read from the object file header.
+func (r *Reader) Flags() uint32 {
+       return r.h.Flags
+}

diff --git a/src/cmd/internal/obj/objfile2.go b/src/cmd/internal/obj/objfile2.go
index 843f6fb5eafc1b0a25522296a3427cc59f4a8471..f3389612d6c422a775794a0210bbc787dace3b12 100644 (file)
--- a/src/cmd/internal/obj/objfile2.go
+++ b/src/cmd/internal/obj/objfile2.go
@@ -35,7 +35,11 @@ func WriteObjFile2(ctxt *Link, b *bio.Writer, pkgpath string) {
 
        // Header
        // We just reserve the space. We'll fill in the offsets later.
-       h := goobj2.Header{Magic: goobj2.Magic}
+       flags := uint32(0)
+       if ctxt.Flag_shared {
+               flags |= goobj2.ObjFlagShared
+       }
+       h := goobj2.Header{Magic: goobj2.Magic, Flags: flags}
        h.Write(w.Writer)
 
        // String table
@@ -231,9 +235,6 @@ func (w *writer) Sym(s *LSym) {
        if s.ReflectMethod() {
                flag |= goobj2.SymFlagReflectMethod
        }
-       if w.ctxt.Flag_shared { // This is really silly
-               flag |= goobj2.SymFlagShared
-       }
        if s.TopFrame() {
                flag |= goobj2.SymFlagTopFrame
        }

diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 1cd44fd1b6af5d8ffb69cb5687c227f05b046fd4..c155f27dcbc2aaa0ad4bcae126970a277ca43234 100644 (file)
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -56,7 +56,8 @@ type Reloc struct {
 type oReader struct {
        *goobj2.Reader
        unit      *sym.CompilationUnit
-       version   int // version of static symbol
+       version   int    // version of static symbol
+       flags     uint32 // read from object file
        pkgprefix string
 }
 
@@ -460,7 +461,7 @@ func (l *Loader) Preload(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *
        }
        localSymVersion := syms.IncVersion()
        pkgprefix := objabi.PathToPrefix(lib.Pkg) + "."
-       or := &oReader{r, unit, localSymVersion, pkgprefix}
+       or := &oReader{r, unit, localSymVersion, r.Flags(), pkgprefix}
 
        // Autolib
        lib.ImportStrings = append(lib.ImportStrings, r.Autolib()...)
@@ -770,7 +771,7 @@ func loadObjFull(l *Loader, r *oReader) {
                if osym.ReflectMethod() {
                        s.Attr |= sym.AttrReflectMethod
                }
-               if osym.Shared() {
+               if r.Flags()&goobj2.ObjFlagShared != 0 {
                        s.Attr |= sym.AttrShared
                }
                if osym.TopFrame() {