fix: support DW_RLE_startx_length range entries

cmd/stackwhere/list_test.go

@@ -282,3 +282,30 @@ func TestListCollectionJSONOrdersEqualUsageByName(t *testing.T) {
 		t.Fatalf("unexpected JSON output: got %#v want %#v", got, want)
 	}
 }
+
+func TestListProgramSupportsStartXLengthRangeLists(t *testing.T) {
+	cmd := root()
+	cmd.SetArgs([]string{"list", "../../testdata/noinline.o", "entry", "-j"})
+
+	var stdout bytes.Buffer
+	cmd.SetOut(&stdout)
+
+	if err := cmd.Execute(); err != nil {
+		t.Fatalf("list command failed: %v", err)
+	}
+
+	var got slotList
+	if err := json.Unmarshal(stdout.Bytes(), &got); err != nil {
+		t.Fatalf("failed to decode JSON output: %v", err)
+	}
+
+	want := slotList{
+		{
+			{Offset: 4, Name: "r1", ByteSize: -1},
+		},
+	}
+	if len(got) != len(want) || len(got[0]) != len(want[0]) ||
+		got[0][0].Offset != want[0][0].Offset || got[0][0].Name != want[0][0].Name || got[0][0].ByteSize != want[0][0].ByteSize {
+		t.Fatalf("unexpected JSON output: got %#v want %#v", got, want)
+	}
+}

internal/dwarf/rangelist.go

@@ -42,8 +42,8 @@ const (
 	DW_RLE_end_of_list   rangelistDescriptorCode = 0x00
 	DW_RLE_base_addressx rangelistDescriptorCode = 0x01
 	// DW_RLE_startx_endx      = 0x02
-	// DW_RLE_startx_length    = 0x03
-	DW_RLE_offset_pair rangelistDescriptorCode = 0x04
+	DW_RLE_startx_length rangelistDescriptorCode = 0x03
+	DW_RLE_offset_pair   rangelistDescriptorCode = 0x04
 	// DW_RLE_base_address = 0x05
 	// DW_RLE_start_end     = 0x06
 	// DW_RLE_start_length = 0x07
@@ -167,6 +167,29 @@ loop:
 				if idx < uint64(len(debugAddrs)) {
 					currentBase = debugAddrs[idx]
 				}
+			case DW_RLE_startx_length:
+				var startIdx, length uint64
+				var l uint32
+				startIdx, l, err = leb128.DecodeUnsigned(r)
+				if err != nil {
+					return nil, fmt.Errorf("error parsing startx length entry: %w", err)
+				}
+				off += uint64(l)
+
+				length, l, err = leb128.DecodeUnsigned(r)
+				if err != nil {
+					return nil, fmt.Errorf("error parsing startx length entry: %w", err)
+				}
+				off += uint64(l)
+
+				if startIdx >= uint64(len(debugAddrs)) {
+					return nil, fmt.Errorf("startx length entry references invalid debug address index: %d", startIdx)
+				}
+
+				entry.Ranges = append(entry.Ranges, Range{
+					Start: debugAddrs[startIdx],
+					End:   debugAddrs[startIdx] + length,
+				})
 			case DW_RLE_offset_pair:
 				var rng Range
 				var l uint32

testdata/Makefile

@@ -20,6 +20,7 @@ docker:
 TARGETS := \
 	basic \
 	equal \
+	noinline \
 	spill
 
 .PHONY: all

testdata/noinline.c

@@ -0,0 +1,15 @@
+#define __section(X) __attribute__((section(X), used))
+#define __noinline __attribute__((noinline))
+
+static __noinline void helper(int *value)
+{
+	*value = 42;
+}
+
+__section("tc") int entry(void *ctx)
+{
+	int value = 0;
+
+	helper(&value);
+	return value;
+}