Avoiding closing over HEAPU32/HEAPU64 in emval.js (#17556)

Its not generally save to close over these variables because they
get re-bound on memory growth.

See https://github.com/emscripten-core/emscripten/pull/17293/files/6cd449dba7419e3393962a7c0a6ee6d6d1f8a295#r933701376

Author: sbc100

src/embind/emval.js

@@ -201,8 +201,15 @@ var LibraryEmVal = {
       argsList += (i!==0?", ":"")+"arg"+i; // 'arg0, arg1, ..., argn'
     }
 
+    // The body of the generated function does not have access to enclosing
+    // scope where HEAPU64/HEAPU32/etc are defined, and we cannot pass them
+    // directly as arguments (like we do the Module object) since memory
+    // growth can cause them to be re-bound.
+    var getMemory = () => {{{ MEMORY64 ? "HEAPU64" : "HEAPU32" }}};
+
     var functionBody =
-        "return function emval_allocator_"+argCount+"(constructor, argTypes, args) {\n";
+        "return function emval_allocator_"+argCount+"(constructor, argTypes, args) {\n" +
+        "  var {{{ MEMORY64 ? 'HEAPU64' : 'HEAPU32' }}} = getMemory();\n";
 
     for (var i = 0; i < argCount; ++i) {
         functionBody +=
@@ -217,8 +224,8 @@ var LibraryEmVal = {
         "}\n";
 
     /*jshint evil:true*/
-    return (new Function("requireRegisteredType", "Module", "valueToHandle", "{{{ MEMORY64 ? "HEAPU64" : "HEAPU32" }}}" , functionBody))(
-        requireRegisteredType, Module, Emval.toHandle, {{{ MEMORY64 ? "HEAPU64" : "HEAPU32" }}});
+    return (new Function("requireRegisteredType", "Module", "valueToHandle", "getMemory" , functionBody))(
+        requireRegisteredType, Module, Emval.toHandle, getMemory);
 #endif
   },
 

test/embind/embind_test.cpp

@@ -7,6 +7,8 @@
 #include <malloc.h>
 #include <functional>
 #include <emscripten/bind.h>
+#include <emscripten/heap.h>
+#include <emscripten/em_asm.h>
 
 using namespace emscripten;
 
@@ -192,8 +194,14 @@ std::u32string get_literal_u32string() {
 
 void force_memory_growth() {
     val module = val::global("Module");
-    std::size_t heap_size = module["HEAPU8"]["byteLength"].as<size_t>();
-    free(malloc(heap_size + 1));
+    std::size_t old_size = emscripten_get_heap_size();
+    EM_ASM({"globalThis.oldheap = HEAPU8;"});
+    assert(val::global("oldheap")["byteLength"].as<size_t>() == old_size);
+    emscripten_resize_heap(old_size + EMSCRIPTEN_PAGE_SIZE);
+    assert(emscripten_get_heap_size() > old_size);
+    // global HEAPU8 should now be rebound, and our oldheap should be detached
+    assert(module["HEAPU8"]["byteLength"].as<size_t>() > old_size);
+    assert(val::global("oldheap")["byteLength"].as<size_t>() == 0);
 }
 
 std::string emval_test_take_and_return_const_char_star(const char* str) {