Fix passing large arrays with JS values into Wasm detaching memory

CHANGELOG.md

@@ -28,6 +28,9 @@
     3. The name of an imported function if the function is not a method and does not have a `js_namespace` or `module` attribute.
   - Using JS keywords on imports in places other than the above will no longer cause the keywords to be escaped as `_{keyword}`.
 
+* Fixed passing large arrays into Rust failing because of internal memory allocations invalidating the memory buffer.
+  [#4353](https://github.com/rustwasm/wasm-bindgen/pull/4353)
+
 --------------------------------------------------------------------------------
 
 ## [0.2.99](https://github.com/rustwasm/wasm-bindgen/compare/0.2.98...0.2.99)

crates/cli-support/src/js/mod.rs

@@ -1621,34 +1621,32 @@ __wbg_set_wasm(wasm);"
                 let add = self.expose_add_to_externref_table(table, alloc)?;
                 self.global(&format!(
                     "
-                        function {}(array, malloc) {{
+                        function {ret}(array, malloc) {{
                             const ptr = malloc(array.length * 4, 4) >>> 0;
-                            const mem = {}();
                             for (let i = 0; i < array.length; i++) {{
-                                mem.setUint32(ptr + 4 * i, {}(array[i]), true);
+                                const add = {add}(array[i]);
+                                {mem}().setUint32(ptr + 4 * i, add, true);
                             }}
                             WASM_VECTOR_LEN = array.length;
                             return ptr;
                         }}
                     ",
-                    ret, mem, add,
                 ));
             }
             _ => {
                 self.expose_add_heap_object();
                 self.global(&format!(
                     "
-                        function {}(array, malloc) {{
+                        function {ret}(array, malloc) {{
                             const ptr = malloc(array.length * 4, 4) >>> 0;
-                            const mem = {}();
+                            const mem = {mem}();
                             for (let i = 0; i < array.length; i++) {{
                                 mem.setUint32(ptr + 4 * i, addHeapObject(array[i]), true);
                             }}
                             WASM_VECTOR_LEN = array.length;
                             return ptr;
                         }}
                     ",
-                    ret, mem,
                 ));
             }
         }

crates/cli/tests/reference/echo.js

@@ -666,9 +666,9 @@ function addToExternrefTable0(obj) {
 
 function passArrayJsValueToWasm0(array, malloc) {
     const ptr = malloc(array.length * 4, 4) >>> 0;
-    const mem = getDataViewMemory0();
     for (let i = 0; i < array.length; i++) {
-        mem.setUint32(ptr + 4 * i, addToExternrefTable0(array[i]), true);
+        const add = addToExternrefTable0(array[i]);
+        getDataViewMemory0().setUint32(ptr + 4 * i, add, true);
     }
     WASM_VECTOR_LEN = array.length;
     return ptr;

crates/cli/tests/reference/typescript-type.js

@@ -49,9 +49,9 @@ function addToExternrefTable0(obj) {
 
 function passArrayJsValueToWasm0(array, malloc) {
     const ptr = malloc(array.length * 4, 4) >>> 0;
-    const mem = getDataViewMemory0();
     for (let i = 0; i < array.length; i++) {
-        mem.setUint32(ptr + 4 * i, addToExternrefTable0(array[i]), true);
+        const add = addToExternrefTable0(array[i]);
+        getDataViewMemory0().setUint32(ptr + 4 * i, add, true);
     }
     WASM_VECTOR_LEN = array.length;
     return ptr;

tests/wasm/js_vec.js

@@ -0,0 +1,8 @@
+const assert = require('assert');
+const wasm = require('wasm-bindgen-test');
+
+// Test if passing large arrays which cause allocation in Wasm are properly handled.
+exports.pass_array_with_allocation = () => {
+    const values = new Array(10_000).fill(1)
+    assert.strictEqual(wasm.test_sum(values), 10_000);
+};

tests/wasm/js_vec.rs

@@ -0,0 +1,24 @@
+use js_sys::Number;
+use wasm_bindgen::prelude::wasm_bindgen;
+use wasm_bindgen_test::wasm_bindgen_test;
+
+#[wasm_bindgen(module = "tests/wasm/js_vec.js")]
+extern "C" {
+    fn pass_array_with_allocation();
+}
+
+#[wasm_bindgen]
+pub fn test_sum(param: Vec<Number>) -> f64 {
+    let mut sum = 0.;
+
+    for data in param {
+        sum += data.value_of();
+    }
+
+    sum
+}
+
+#[wasm_bindgen_test]
+fn test() {
+    pass_array_with_allocation();
+}

tests/wasm/main.rs

@@ -40,6 +40,7 @@ pub mod inner_self;
 pub mod intrinsics;
 pub mod js_keywords;
 pub mod js_objects;
+pub mod js_vec;
 pub mod jscast;
 pub mod link_to;
 pub mod macro_rules;