internal/gcimporter: restore logical line numbers for cgo exports

go/packages/packages_test.go

@@ -3843,3 +3843,35 @@ import _ "errors"
 		t.Errorf("packages checked = %v, want a and errors", checked)
 	}
 }
+
+func TestCgoExportDataPosition(t *testing.T) {
+	testAllOrModulesParallel(t, func(t *testing.T, exporter packagestest.Exporter) {
+		testenv.NeedsTool(t, "cgo")
+		exported := packagestest.Export(t, exporter, []packagestest.Module{{
+			Name: "golang.org/fake",
+			Files: map[string]any{
+				"c/c.go": "package c\nimport \"C\"\n\nfunc F() {}\n\n//line c.go:70000\nfunc G() {}\nfunc H() {}\n",
+				"p/p.go": "package p\nimport \"golang.org/fake/c\"\nvar _, _, _ = c.F, c.G, c.H\n",
+			},
+		}})
+		exported.Config.Env = append(exported.Config.Env, "CGO_ENABLED=1")
+		exported.Config.Mode = packages.LoadSyntax
+		pkgs, err := packages.Load(exported.Config, "golang.org/fake/p")
+		if err != nil || len(pkgs) != 1 || len(pkgs[0].Errors) != 0 {
+			t.Fatalf("Load: %v, %v", pkgs, err)
+		}
+		wantLines := map[string]int{"F": 4, "G": 70000, "H": 70001}
+		for id, obj := range pkgs[0].TypesInfo.Uses {
+			if want, ok := wantLines[id.Name]; ok {
+				pos := pkgs[0].Fset.Position(obj.Pos())
+				if filepath.Base(pos.Filename) != "c.go" || pos.Line != want {
+					t.Errorf("position of c.%s = %v, want c.go:%d", id.Name, pos, want)
+				}
+				delete(wantLines, id.Name)
+			}
+		}
+		for name := range wantLines {
+			t.Errorf("missing use of c.%s", name)
+		}
+	})
+}

internal/gcimporter/bimport.go

@@ -24,7 +24,12 @@ const deltaNewFile = -64 // see cmd/compile/internal/gc/bexport.go
 // Synthesize a token.Pos
 type fakeFileSet struct {
 	fset  *token.FileSet
-	files map[string]*fileInfo
+	files map[fileKey]*fileInfo
+}
+
+type fileKey struct {
+	name     string
+	lineBase int
 }
 
 type fileInfo struct {
@@ -37,17 +42,21 @@ const maxlines = 64 * 1024
 func (s *fakeFileSet) pos(file string, line, column int) token.Pos {
 	_ = column // TODO(mdempsky): Make use of column.
 
-	// Since we don't know the set of needed file positions, we reserve maxlines
-	// positions per file. We delay calling token.File.SetLines until all
-	// positions have been calculated (by way of fakeFileSet.setLines), so that
-	// we can avoid setting unnecessary lines. See also golang/go#46586.
-	f := s.files[file]
+	// Use fixed-size windows so high line numbers can share the same
+	// line table. Delay SetLines until all positions have been calculated
+	// to avoid setting unnecessary lines. See golang/go#46586.
+	key := fileKey{name: file}
+	if line > maxlines {
+		key.lineBase = (line - 1) / maxlines * maxlines
+		line -= key.lineBase
+	}
+	f := s.files[key]
 	if f == nil {
 		f = &fileInfo{file: s.fset.AddFile(file, -1, maxlines)}
-		s.files[file] = f
-	}
-	if line > maxlines {
-		line = 1
+		if key.lineBase != 0 {
+			f.file.AddLineColumnInfo(0, file, key.lineBase+1, 1)
+		}
+		s.files[key] = f
 	}
 	if line > f.lastline {
 		f.lastline = line

internal/gcimporter/iimport.go

@@ -223,7 +223,7 @@ func iimportCommon(fset *token.FileSet, getPackages GetPackagesFunc, data []byte
 
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*fileInfo),
+			files: make(map[fileKey]*fileInfo),
 		},
 	}
 	defer p.fake.setLines() // set lines for files in fset

internal/gcimporter/ureader.go

@@ -29,7 +29,7 @@ type pkgReader struct {
 
 	// lazily initialized arrays corresponding to the unified IR
 	// PosBase, Pkg, and Type sections, respectively.
-	posBases []string // position bases (i.e., file names)
+	posBases []positionBase
 	pkgs     []*types.Package
 	typs     []types.Type
 
@@ -96,13 +96,13 @@ func readUnifiedPackage(fset *token.FileSet, ctxt *types.Context, imports map[st
 
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*fileInfo),
+			files: make(map[fileKey]*fileInfo),
 		},
 
 		ctxt:    ctxt,
 		imports: imports,
 
-		posBases: make([]string, input.NumElems(pkgbits.RelocPosBase)),
+		posBases: make([]positionBase, input.NumElems(pkgbits.RelocPosBase)),
 		pkgs:     make([]*types.Package, input.NumElems(pkgbits.RelocPkg)),
 		typs:     make([]types.Type, input.NumElems(pkgbits.RelocType)),
 	}
@@ -194,52 +194,43 @@ func (pr *pkgReader) retireReader(r *reader) {
 
 // @@@ Positions
 
+type positionBase struct {
+	filename   string
+	lineOffset int
+}
+
 func (r *reader) pos() token.Pos {
 	r.Sync(pkgbits.SyncPos)
 	if !r.Bool() {
 		return token.NoPos
 	}
 
 	// TODO(mdempsky): Delta encoding.
-	posBase := r.posBase()
-	line := r.Uint()
-	col := r.Uint()
-	return r.p.fake.pos(posBase, int(line), int(col))
-}
-
-func (r *reader) posBase() string {
-	return r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase))
+	base := r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase))
+	line := int(r.Uint()) + base.lineOffset
+	col := int(r.Uint())
+	return r.p.fake.pos(base.filename, line, col)
 }
 
-func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) string {
-	if b := pr.posBases[idx]; b != "" {
+func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) positionBase {
+	if b := pr.posBases[idx]; b.filename != "" {
 		return b
 	}
 
-	var filename string
-	{
-		r := pr.tempReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
-
-		// Within types2, position bases have a lot more details (e.g.,
-		// keeping track of where //line directives appeared exactly).
-		//
-		// For go/types, we just track the file name.
-
-		filename = r.String()
-
-		if r.Bool() { // file base
-			// Was: "b = token.NewTrimmedFileBase(filename, true)"
-		} else { // line base
-			pos := r.pos()
-			line := r.Uint()
-			col := r.Uint()
-
-			// Was: "b = token.NewLineBase(pos, filename, true, line, col)"
-			_, _, _ = pos, line, col
+	r := pr.tempReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
+	b := positionBase{filename: r.String()}
+	if !r.Bool() { // line directive
+		r.Sync(pkgbits.SyncPos)
+		var physicalLine int
+		if r.Bool() {
+			r.Reloc(pkgbits.RelocPosBase)
+			physicalLine = int(r.Uint())
+			r.Uint() // physical column
 		}
-		pr.retireReader(r)
+		b.lineOffset = int(r.Uint()) - physicalLine
+		r.Uint() // directive column
 	}
-	b := filename
+	pr.retireReader(r)
 	pr.posBases[idx] = b
 	return b
 }