cmd/link: change -strictdups checking to handle mix of flags

Update the recently-added '-strictdups' sanity checking to avoid
failing the link in cases where we have objects feeding into the link
with a mix of command line flags (and in particular some with "-N" and
some without). This scenario will trigger errors/warnings due to
inlinable functions and wrapper functions that have different sizes
due to presence or lack of optimization.

Update #31034.

Change-Id: I1dd9e37c2f9bea5da0ab82e32e6fc210aebf6a65
Reviewed-on: https://go-review.googlesource.com/c/go/+/169160
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

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

@@ -1797,6 +1797,7 @@ func dwarfGenerateDebugInfo(ctxt *Link) {
 
 	// fake root DIE for compile unit DIEs
 	var dwroot dwarf.DWDie
+	flagVariants := make(map[string]bool)
 
 	for _, lib := range ctxt.Library {
 		unit := &compilationUnit{lib: lib}
@@ -1825,7 +1826,11 @@ func dwarfGenerateDebugInfo(ctxt *Link) {
 			// version, so it should be safe for readers to scan
 			// forward to the semicolon.
 			producer += "; " + string(producerExtra.P)
+			flagVariants[string(producerExtra.P)] = true
+		} else {
+			flagVariants[""] = true
 		}
+
 		newattr(unit.dwinfo, dwarf.DW_AT_producer, dwarf.DW_CLS_STRING, int64(len(producer)), producer)
 
 		if len(lib.Textp) == 0 {
@@ -1876,6 +1881,13 @@ func dwarfGenerateDebugInfo(ctxt *Link) {
 		}
 	}
 
+	// Fix for 31034: if the objects feeding into this link were compiled
+	// with different sets of flags, then don't issue an error if
+	// the -strictdups checks fail.
+	if checkStrictDups > 1 && len(flagVariants) > 1 {
+		checkStrictDups = 1
+	}
+
 	// Create DIEs for global variables and the types they use.
 	genasmsym(ctxt, defdwsymb)
 

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

@@ -200,6 +200,10 @@ var (
 
 	nerrors  int
 	liveness int64
+
+	// See -strictdups command line flag.
+	checkStrictDups   int // 0=off 1=warning 2=error
+	strictDupMsgCount int
 )
 
 var (
@@ -283,6 +287,9 @@ func errorexit() {
 	if nerrors != 0 {
 		Exit(2)
 	}
+	if checkStrictDups > 1 && strictDupMsgCount > 0 {
+		Exit(2)
+	}
 	Exit(0)
 }
 
@@ -1745,7 +1752,8 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 	default:
 		log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
 	}
-	objfile.Load(ctxt.Arch, ctxt.Syms, f, lib, eof-f.Offset(), pn, flags)
+	c := objfile.Load(ctxt.Arch, ctxt.Syms, f, lib, eof-f.Offset(), pn, flags)
+	strictDupMsgCount += c
 	addImports(ctxt, lib, pn)
 	return nil
 }

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

@@ -148,6 +148,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 	if objabi.Fieldtrack_enabled != 0 {
 		ctxt.Reachparent = make(map[*sym.Symbol]*sym.Symbol)
 	}
+	checkStrictDups = *FlagStrictDups
 
 	startProfile()
 	if ctxt.BuildMode == BuildModeUnset {

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

@@ -42,6 +42,7 @@ type objReader struct {
 	dupSym          *sym.Symbol
 	localSymVersion int
 	flags           int
+	strictDupMsgs   int
 
 	// rdBuf is used by readString and readSymName as scratch for reading strings.
 	rdBuf []byte
@@ -72,7 +73,7 @@ const (
 
 // 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, flags int) {
+func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, length int64, pn string, flags int) int {
 	start := f.Offset()
 	r := &objReader{
 		rd:              f.Reader,
@@ -88,6 +89,7 @@ func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, le
 	if f.Offset() != start+length {
 		log.Fatalf("%s: unexpected end at %d, want %d", pn, f.Offset(), start+length)
 	}
+	return r.strictDupMsgs
 }
 
 func (r *objReader) loadObjFile() {
@@ -376,9 +378,8 @@ overwrite:
 			// params; I am guessing that the pos is being inherited
 			// from the spot where the wrapper is needed.
 			whitelist := strings.HasPrefix(dup.Name, "go.info.go.interface")
-
-			if r.flags&StrictDupsErrFlag != 0 && !whitelist {
-				log.Fatalf("failed duplicate symbol check on '%s' reading %s", dup.Name, r.pn)
+			if !whitelist {
+				r.strictDupMsgs++
 			}
 		}
 	}