cmd/compile: fix dwarf ranges of inlined subroutine entries

DWARF ranges are half-open.

Fixes #23928

Change-Id: I71b3384d1bc2c65bd37ca8a02a0b7ff48fec3688
Reviewed-on: https://go-review.googlesource.com/94816Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/dwinl.go

@@ -161,15 +161,15 @@ func assembleInlines(fnsym *obj.LSym, fn *Node, dwVars []*dwarf.Var) dwarf.InlCa
 			continue
 		} else {
 			// Close out the current range
-			endRange(crange, prevp)
+			endRange(crange, p)
 
 			// Begin new range
 			crange = beginRange(inlcalls.Calls, p, ii, imap)
 			curii = ii
 		}
 	}
-	if prevp != nil {
-		endRange(crange, prevp)
+	if crange != nil {
+		crange.End = fnsym.Size
 	}
 
 	// Debugging

src/cmd/compile/internal/gc/scope_test.go

@@ -218,7 +218,7 @@ func TestScopeRanges(t *testing.T) {
 	}
 	defer os.RemoveAll(dir)
 
-	src, f := gobuild(t, dir, testfile)
+	src, f := gobuild(t, dir, false, testfile)
 	defer f.Close()
 
 	// the compiler uses forward slashes for paths even on windows
@@ -409,7 +409,7 @@ func (scope *lexblock) markLines(pcln objfile.Liner, lines map[line][]*lexblock)
 	}
 }
 
-func gobuild(t *testing.T, dir string, testfile []testline) (string, *objfile.File) {
+func gobuild(t *testing.T, dir string, optimized bool, testfile []testline) (string, *objfile.File) {
 	src := filepath.Join(dir, "test.go")
 	dst := filepath.Join(dir, "out.o")
 
@@ -423,7 +423,13 @@ func gobuild(t *testing.T, dir string, testfile []testline) (string, *objfile.Fi
 	}
 	f.Close()
 
-	cmd := exec.Command(testenv.GoToolPath(t), "build", "-gcflags=-N -l", "-o", dst, src)
+	args := []string{"build"}
+	if !optimized {
+		args = append(args, "-gcflags=-N -l")
+	}
+	args = append(args, "-o", dst, src)
+
+	cmd := exec.Command(testenv.GoToolPath(t), args...)
 	if b, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("build: %s\n", string(b))
 		t.Fatal(err)
@@ -435,3 +441,48 @@ func gobuild(t *testing.T, dir string, testfile []testline) (string, *objfile.Fi
 	}
 	return src, pkg
 }
+
+// TestEmptyDwarfRanges tests that no list entry in debug_ranges has start == end.
+// See issue #23928.
+func TestEmptyDwarfRanges(t *testing.T) {
+	testenv.MustHaveGoRun(t)
+
+	dir, err := ioutil.TempDir("", "TestEmptyDwarfRanges")
+	if err != nil {
+		t.Fatalf("could not create directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	_, f := gobuild(t, dir, true, []testline{{line: "package main"}, {line: "func main(){ println(\"hello\") }"}})
+	defer f.Close()
+
+	dwarfData, err := f.DWARF()
+	if err != nil {
+		t.Fatal(err)
+	}
+	dwarfReader := dwarfData.Reader()
+
+	for {
+		entry, err := dwarfReader.Next()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if entry == nil {
+			break
+		}
+
+		ranges, err := dwarfData.Ranges(entry)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if ranges == nil {
+			continue
+		}
+
+		for _, rng := range ranges {
+			if rng[0] == rng[1] {
+				t.Errorf("range entry with start == end: %v", rng)
+			}
+		}
+	}
+}