1 files changed, 119 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/dwarf_test.go b/src/cmd/link/internal/ld/dwarf_test.go
index fb9c45b07d..f3dd53792a 100644
--- a/src/cmd/link/internal/ld/dwarf_test.go
+++ b/src/cmd/link/internal/ld/dwarf_test.go
@@ -1479,3 +1479,122 @@ func TestIssue38192(t *testing.T) {
 		t.Logf("row %d: A=%x F=%s L=%d\n", i, r.Address, r.File.Name, r.Line)
 	}
 }
+
+func TestIssue39757(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping on plan9; no DWARF symbol table in executables")
+	}
+
+	// In this bug the DWARF line table contents for the last couple of
+	// instructions in a function were incorrect (bad file/line). This
+	// test verifies that all of the line table rows for a function
+	// of interest have the same file (no "autogenerated").
+	//
+	// Note: the function in this test was written with an eye towards
+	// ensuring that there are no inlined routines from other packages
+	// (which could introduce other source files into the DWARF); it's
+	// possible that at some point things could evolve in the
+	// compiler/runtime in ways that aren't happening now, so this
+	// might be something to check for if it does start failing.
+
+	tmpdir, err := ioutil.TempDir("", "TestIssue38192")
+	if err != nil {
+		t.Fatalf("could not create directory: %v", err)
+	}
+	defer os.RemoveAll(tmpdir)
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("where am I? %v", err)
+	}
+	pdir := filepath.Join(wd, "testdata", "issue39757")
+	f := gobuildTestdata(t, tmpdir, pdir, DefaultOpt)
+
+	syms, err := f.Symbols()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var addr uint64
+	for _, sym := range syms {
+		if sym.Name == "main.main" {
+			addr = sym.Addr
+			break
+		}
+	}
+	if addr == 0 {
+		t.Fatal("cannot find main.main in symbols")
+	}
+
+	// Open the resulting binary and examine the DWARF it contains.
+	// Look for the function of interest ("main.main")
+	// and verify that all line table entries show the same source
+	// file.
+	dw, err := f.DWARF()
+	if err != nil {
+		t.Fatalf("error parsing DWARF: %v", err)
+	}
+	rdr := dw.Reader()
+	ex := examiner{}
+	if err := ex.populate(rdr); err != nil {
+		t.Fatalf("error reading DWARF: %v", err)
+	}
+
+	// Locate the main.main DIE
+	mains := ex.Named("main.main")
+	if len(mains) == 0 {
+		t.Fatalf("unable to locate DIE for main.main")
+	}
+	if len(mains) != 1 {
+		t.Fatalf("more than one main.main DIE")
+	}
+	maindie := mains[0]
+
+	// Collect the start/end PC for main.main
+	lowpc := maindie.Val(dwarf.AttrLowpc).(uint64)
+	highpc := maindie.Val(dwarf.AttrHighpc).(uint64)
+
+	// Now read the line table for the 'main' compilation unit.
+	mainIdx := ex.idxFromOffset(maindie.Offset)
+	cuentry := ex.Parent(mainIdx)
+	if cuentry == nil {
+		t.Fatalf("main.main DIE appears orphaned")
+	}
+	lnrdr, lerr := dw.LineReader(cuentry)
+	if lerr != nil {
+		t.Fatalf("error creating DWARF line reader: %v", err)
+	}
+	if lnrdr == nil {
+		t.Fatalf("no line table for main.main compilation unit")
+	}
+	rows := []dwarf.LineEntry{}
+	mainrows := 0
+	var lne dwarf.LineEntry
+	for {
+		err := lnrdr.Next(&lne)
+		if err == io.EOF {
+			break
+		}
+		rows = append(rows, lne)
+		if err != nil {
+			t.Fatalf("error reading next DWARF line: %v", err)
+		}
+		if lne.Address < lowpc || lne.Address > highpc {
+			continue
+		}
+		if !strings.HasSuffix(lne.File.Name, "issue39757main.go") {
+			t.Errorf("found row with file=%s (not issue39757main.go)", lne.File.Name)
+		}
+		mainrows++
+	}
+	f.Close()
+
+	// Make sure we saw a few rows.
+	if mainrows < 3 {
+		t.Errorf("not enough line table rows for main.main (got %d, wanted > 3", mainrows)
+		for i, r := range rows {
+			t.Logf("row %d: A=%x F=%s L=%d\n", i, r.Address, r.File.Name, r.Line)
+		}
+	}
+}