Restore the stack pointer when a JS measure function throws

javascript/CMakeLists.txt

@@ -49,7 +49,7 @@ add_link_options(
     # both bundlders and Node.
     "SHELL:-s SINGLE_FILE=1"
     "SHELL:-s ENVIRONMENT='web'"
-    "SHELL:-s EXPORTED_RUNTIME_METHODS=['HEAPF32','HEAP32']"
+    "SHELL:-s EXPORTED_RUNTIME_METHODS=['HEAPF32','HEAP32','stackSave','stackRestore']"
     "SHELL:-Wl,--export-dynamic")
 
 add_library(yogaObjLib OBJECT ${YOGA_SOURCES} ${BRIDGE_SOURCES})

javascript/src/wrapAssembly.ts

@@ -939,7 +939,16 @@ export default function wrapAssembly(lib: any): Yoga {
       height: number | 'auto' | undefined = NaN,
       direction: Direction = Direction.LTR,
     ): void {
-      lib._YGNodeCalculateLayout(this._ptr, width, height, direction);
+      // An exception thrown by a measure function unwinds the WebAssembly
+      // frames of the layout without restoring the stack pointer. Restore it,
+      // or repeated exceptions overflow the stack into static memory.
+      const stack = lib.stackSave();
+      try {
+        lib._YGNodeCalculateLayout(this._ptr, width, height, direction);
+      } catch (e) {
+        lib.stackRestore(stack);
+        throw e;
+      }
     }
 
     // --- Layout getters ---

javascript/tests/YGMeasureTest.test.ts

@@ -64,3 +64,80 @@ test('dont_fail_with_incomplete_measure_dimensions', () => {
   expect(node3.getComputedWidth()).toBe(100);
   expect(node3.getComputedHeight()).toBe(0);
 });
+
+function createTreeWithThrowingMeasureFunc(depth: number) {
+  const root = Yoga.Node.create();
+  let parent = root;
+  for (let i = 0; i < depth; i++) {
+    const child = Yoga.Node.create();
+    parent.insertChild(child, 0);
+    parent = child;
+  }
+
+  const leaf = Yoga.Node.create();
+  leaf.setMeasureFunc(() => {
+    throw new Error('measure failed');
+  });
+  parent.insertChild(leaf, 0);
+
+  return root;
+}
+
+test('measure_func_exception_propagates_to_caller', () => {
+  const root = createTreeWithThrowingMeasureFunc(0);
+
+  expect(() =>
+    root.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR),
+  ).toThrow('measure failed');
+});
+
+test('layout_works_after_repeated_measure_func_exceptions', () => {
+  // Without restoring the stack pointer, this breaks after about 18 throws.
+  for (let i = 0; i < 1000; i++) {
+    const root = createTreeWithThrowingMeasureFunc(20);
+    expect(() =>
+      root.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR),
+    ).toThrow('measure failed');
+  }
+
+  const root = Yoga.Node.create();
+  root.setWidth(100);
+  root.setHeight(100);
+  root.setAlignItems(Yoga.ALIGN_FLEX_START);
+
+  const root_child0 = Yoga.Node.create();
+  root_child0.setMeasureFunc(() => ({width: 10, height: 10}));
+  root.insertChild(root_child0, 0);
+  root.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR);
+
+  expect(root_child0.getComputedWidth()).toBe(10);
+  expect(root_child0.getComputedHeight()).toBe(10);
+});
+
+test('node_is_measured_again_after_its_measure_func_threw', () => {
+  let shouldThrow = true;
+
+  const root = Yoga.Node.create();
+  root.setWidth(100);
+  root.setHeight(100);
+  root.setAlignItems(Yoga.ALIGN_FLEX_START);
+
+  const root_child0 = Yoga.Node.create();
+  root_child0.setMeasureFunc(() => {
+    if (shouldThrow) {
+      throw new Error('measure failed');
+    }
+    return {width: 10, height: 20};
+  });
+  root.insertChild(root_child0, 0);
+
+  expect(() =>
+    root.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR),
+  ).toThrow('measure failed');
+
+  shouldThrow = false;
+  root.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR);
+
+  expect(root_child0.getComputedWidth()).toBe(10);
+  expect(root_child0.getComputedHeight()).toBe(20);
+});