Avoid creating wrapper thunks or wasm exports

In debug builds nothing really changes here since we exported functions still get statically assigned to debug wrappers/thunks. However, after this change, in release builds, if you attempt to access `_foo` (internally) or `Module['_foo']` externally before the module is loaded you will now get `undefined`. Since it was always the case that calling these function would crash anyway, the only effected folks would be folks that take the reference early and then call later. e.g. ``` var myfunc = Module['_foo']; // Run before module is loaded // wait until loaded myfunc(); // This will no longer work. ``` Fixes: #23339
emscripten-core · Jan 15, 2025 · 0ee6b6f · 0ee6b6f
1 parent 8e660ed
commit 0ee6b6f
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Showing 84 changed files with 146 additions and 121 deletions.
diff --git a/src/postamble_minimal.js b/src/postamble_minimal.js
@@ -180,10 +180,10 @@ WebAssembly.instantiate(Module['wasm'], imports).then((output) => {
     wasmOffsetConverter = new WasmOffsetConverter(Module['wasm'], output.module);
 #endif
 
-#if !DECLARE_ASM_MODULE_EXPORTS
-  exportWasmSymbols(wasmExports);
-#else
+#if DECLARE_ASM_MODULE_EXPORTS
   assignWasmExports(wasmExports);
+#else
+  exportWasmSymbols(wasmExports);
 #endif
 #if '$wasmTable' in addedLibraryItems
   wasmTable = wasmExports['__indirect_function_table'];

diff --git a/src/preamble.js b/src/preamble.js
@@ -966,7 +966,9 @@ function getWasmImports() {
     instrumentWasmTableWithAbort();
 #endif
 
-#if !DECLARE_ASM_MODULE_EXPORTS
+#if DECLARE_ASM_MODULE_EXPORTS
+    assignWasmExports(wasmExports);
+#else
     // If we didn't declare the asm exports as top level enties this function
     // is in charge of programmatically exporting them on the global object.
     exportWasmSymbols(wasmExports);

diff --git a/test/other/codesize/test_codesize_cxx_ctors1.gzsize b/test/other/codesize/test_codesize_cxx_ctors1.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_ctors1.jssize b/test/other/codesize/test_codesize_cxx_ctors1.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_ctors2.gzsize b/test/other/codesize/test_codesize_cxx_ctors2.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_ctors2.jssize b/test/other/codesize/test_codesize_cxx_ctors2.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except.gzsize b/test/other/codesize/test_codesize_cxx_except.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except.jssize b/test/other/codesize/test_codesize_cxx_except.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except_wasm.gzsize b/test/other/codesize/test_codesize_cxx_except_wasm.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except_wasm.jssize b/test/other/codesize/test_codesize_cxx_except_wasm.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except_wasm_exnref.gzsize b/test/other/codesize/test_codesize_cxx_except_wasm_exnref.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_except_wasm_exnref.jssize b/test/other/codesize/test_codesize_cxx_except_wasm_exnref.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_lto.gzsize b/test/other/codesize/test_codesize_cxx_lto.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_lto.jssize b/test/other/codesize/test_codesize_cxx_lto.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_mangle.gzsize b/test/other/codesize/test_codesize_cxx_mangle.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_mangle.jssize b/test/other/codesize/test_codesize_cxx_mangle.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_noexcept.gzsize b/test/other/codesize/test_codesize_cxx_noexcept.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_noexcept.jssize b/test/other/codesize/test_codesize_cxx_noexcept.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.gzsize b/test/other/codesize/test_codesize_cxx_wasmfs.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.jssize b/test/other/codesize/test_codesize_cxx_wasmfs.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_files_js_fs.gzsize b/test/other/codesize/test_codesize_files_js_fs.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_files_js_fs.jssize b/test/other/codesize/test_codesize_files_js_fs.jssize
@@ -1 +1 @@
-18820
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diff --git a/test/other/codesize/test_codesize_files_wasmfs.gzsize b/test/other/codesize/test_codesize_files_wasmfs.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_files_wasmfs.jssize b/test/other/codesize/test_codesize_files_wasmfs.jssize
@@ -1 +1 @@
-5984
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diff --git a/test/other/codesize/test_codesize_hello_O0.gzsize b/test/other/codesize/test_codesize_hello_O0.gzsize
@@ -1 +1 @@
-7883
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diff --git a/test/other/codesize/test_codesize_hello_O0.jssize b/test/other/codesize/test_codesize_hello_O0.jssize
@@ -1 +1 @@
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+20969
diff --git a/test/other/codesize/test_codesize_hello_O1.gzsize b/test/other/codesize/test_codesize_hello_O1.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_O1.jssize b/test/other/codesize/test_codesize_hello_O1.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_O2.gzsize b/test/other/codesize/test_codesize_hello_O2.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_O2.jssize b/test/other/codesize/test_codesize_hello_O2.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_O3.gzsize b/test/other/codesize/test_codesize_hello_O3.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_O3.jssize b/test/other/codesize/test_codesize_hello_O3.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_Os.gzsize b/test/other/codesize/test_codesize_hello_Os.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_Os.jssize b/test/other/codesize/test_codesize_hello_Os.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_Oz.gzsize b/test/other/codesize/test_codesize_hello_Oz.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_Oz.jssize b/test/other/codesize/test_codesize_hello_Oz.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_dylink.gzsize b/test/other/codesize/test_codesize_hello_dylink.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_dylink.jssize b/test/other/codesize/test_codesize_hello_dylink.jssize
@@ -1 +1 @@
-13241
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diff --git a/test/other/codesize/test_codesize_hello_wasmfs.gzsize b/test/other/codesize/test_codesize_hello_wasmfs.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_hello_wasmfs.jssize b/test/other/codesize/test_codesize_hello_wasmfs.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize b/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize b/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.gzsize b/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.jssize b/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3.gzsize b/test/other/codesize/test_codesize_mem_O3.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3.jssize b/test/other/codesize/test_codesize_mem_O3.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_grow.gzsize b/test/other/codesize/test_codesize_mem_O3_grow.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_grow.jssize b/test/other/codesize/test_codesize_mem_O3_grow.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_grow_standalone.gzsize b/test/other/codesize/test_codesize_mem_O3_grow_standalone.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_grow_standalone.jssize b/test/other/codesize/test_codesize_mem_O3_grow_standalone.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.jssize b/test/other/codesize/test_codesize_mem_O3_standalone.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_lib.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_lib.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_lib.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_lib.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_narg.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_narg.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.gzsize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_minimal_64.gzsize b/test/other/codesize/test_codesize_minimal_64.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_64.jssize b/test/other/codesize/test_codesize_minimal_64.jssize
@@ -1 +1 @@
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diff --git a/test/other/codesize/test_codesize_minimal_O0.gzsize b/test/other/codesize/test_codesize_minimal_O0.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_O0.jssize b/test/other/codesize/test_codesize_minimal_O0.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_O1.gzsize b/test/other/codesize/test_codesize_minimal_O1.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_O1.jssize b/test/other/codesize/test_codesize_minimal_O1.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_O2.gzsize b/test/other/codesize/test_codesize_minimal_O2.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_O2.jssize b/test/other/codesize/test_codesize_minimal_O2.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_O3.gzsize b/test/other/codesize/test_codesize_minimal_O3.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_O3.jssize b/test/other/codesize/test_codesize_minimal_O3.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_Os.gzsize b/test/other/codesize/test_codesize_minimal_Os.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_Os.jssize b/test/other/codesize/test_codesize_minimal_Os.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_Oz-ctors.gzsize b/test/other/codesize/test_codesize_minimal_Oz-ctors.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize b/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_Oz.gzsize b/test/other/codesize/test_codesize_minimal_Oz.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_Oz.jssize b/test/other/codesize/test_codesize_minimal_Oz.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_esm.gzsize b/test/other/codesize/test_codesize_minimal_esm.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_esm.jssize b/test/other/codesize/test_codesize_minimal_esm.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_pthreads.gzsize b/test/other/codesize/test_codesize_minimal_pthreads.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_pthreads.jssize b/test/other/codesize/test_codesize_minimal_pthreads.jssize
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diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.gzsize b/test/other/codesize/test_codesize_minimal_wasmfs.gzsize
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diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.jssize b/test/other/codesize/test_codesize_minimal_wasmfs.jssize
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diff --git a/test/other/test_unoptimized_code_size.js.size b/test/other/test_unoptimized_code_size.js.size
@@ -1 +1 @@
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diff --git a/test/other/test_unoptimized_code_size_no_asserts.js.size b/test/other/test_unoptimized_code_size_no_asserts.js.size
@@ -1 +1 @@
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diff --git a/test/other/test_unoptimized_code_size_strict.js.size b/test/other/test_unoptimized_code_size_strict.js.size
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diff --git a/tools/emscripten.py b/tools/emscripten.py
@@ -886,9 +886,14 @@ def can_use_await():
 def make_export_wrappers(function_exports):
   assert not settings.MINIMAL_RUNTIME
 
-  wrappers = []
+  # When exports are only available asyncronously we generate an extran assignWasmExports
+  # function.   When they are syncronously available we inline the assignment along
+  # with the declaration.
+  async_exports = (settings.WASM_ASYNC_COMPILATION and not can_use_await()) or settings.PTHREADS
 
-  def install_wrapper(sym):
+  def install_debug_wrapper(sym):
+    if not settings.ASSERTIONS:
+      return False
     # The emscripten stack functions are called very early (by writeStackCookie) before
     # the runtime is initialized so we can't create these wrappers that check for
     # runtimeInitialized.
@@ -901,38 +906,58 @@ def install_wrapper(sym):
     # TODO: Look into removing these, and improving our robustness around thread termination.
     return sym not in {'__trap', 'pthread_self', '_emscripten_proxy_execute_task_queue'}
 
-  for name, types in function_exports.items():
-    nargs = len(types.params)
-    mangled = asmjs_mangle(name)
-    wrapper = 'var %s = ' % mangled
-
-    # TODO(sbc): Can we avoid exporting the dynCall_ functions on the module.
+  def outside_export(mangled):
     should_export = settings.EXPORT_KEEPALIVE and mangled in settings.EXPORTED_FUNCTIONS
+    # TODO(sbc): Can we avoid exporting the dynCall_ functions on the module.
     if (name.startswith('dynCall_') and settings.MODULARIZE != 'instance') or should_export:
       if settings.MODULARIZE == 'instance':
         # Update the export declared at the top level.
-        wrapper += f" __exp_{mangled} = "
+        return f" __exp_{mangled}"
       else:
-        exported = "Module['%s'] = " % mangled
-    else:
-      exported = ''
-    wrapper += exported
-
-    if settings.ASSERTIONS and install_wrapper(name):
-      # With assertions enabled we create a wrapper that are calls get routed through, for
-      # the lifetime of the program.
-      wrapper += f"createExportWrapper('{name}', {nargs});"
-    elif (settings.WASM_ASYNC_COMPILATION and not can_use_await()) or settings.PTHREADS:
-      # With WASM_ASYNC_COMPILATION wrapper will replace the global var and Module var on
-      # first use.
-      args = [f'a{i}' for i in range(nargs)]
-      args = ', '.join(args)
-      wrapper += f"({args}) => ({mangled} = {exported}wasmExports['{name}'])({args});"
-    else:
-      wrapper += f"wasmExports['{name}']"
+        return "Module['%s']" % mangled
 
-    wrappers.append(wrapper)
-  return wrappers
+  rtn = []
+  rtn.append('function assignWasmExports(wasmExports) {')
+  for name, types in function_exports.items():
+    # If a debug wrapper was used then we don't need to update anything, we want to
+    # always use the wrapper, and never the direct export.
+    if install_debug_wrapper(name):
+      continue
+    mangled = asmjs_mangle(name)
+    wrapper = f'  {mangled} = '
+    additional_export = outside_export(mangled)
+    if additional_export:
+      wrapper += additional_export + ' = '
+    wrapper += f"wasmExports['{name}'];"
+    rtn.append(wrapper)
+
+  rtn.append('}')
+
+  rtn.append('')
+  rtn.append('// Exported wasm functions.')
+  if async_exports:
+    rtn.append('// These are declared here but will be remain undefined until async wasm instanatiation is complete.')
+
+  if settings.ASSERTIONS:
+    for name, types in function_exports.items():
+      mangled = asmjs_mangle(name)
+      if install_debug_wrapper(name):
+        # With assertions enabled we create a wrapper that are calls get routed through, for
+        # the lifetime of the program.
+        nargs = len(types.params)
+        additional_export = outside_export(mangled)
+        if additional_export:
+          rtn.append(f"var {mangled} = {additional_export} = createExportWrapper('{name}', {nargs});")
+        else:
+          rtn.append(f"var {mangled} = createExportWrapper('{name}', {nargs});")
+      else:
+        rtn.append(f'var {mangled};')
+  else:
+    mangled = [asmjs_mangle(name) for name in function_exports]
+    sep = ',\n  '
+    rtn.append(f'var {sep.join(mangled)};')
+
+  return rtn
 
 
 def create_receiving(function_exports):
@@ -986,17 +1011,15 @@ def create_module(receiving, metadata, global_exports, library_symbols):
   else:
     module.append('var wasmImports = %s;\n' % sending)
 
+  module.append(receiving)
+
   if not settings.MINIMAL_RUNTIME:
-    if settings.WASM_ASYNC_COMPILATION:
-      if can_use_await():
-        # In modularize mode the generated code is within a factory function.
-        module.append("var wasmExports = await createWasm();\n")
-      else:
-        module.append("var wasmExports;\ncreateWasm();\n")
+    if settings.WASM_ASYNC_COMPILATION and can_use_await():
+      # In modularize mode the generated code is within a factory function.
+      module.append("var wasmExports = await createWasm();\n")
     else:
-      module.append("var wasmExports = createWasm();\n")
+      module.append("var wasmExports;\ncreateWasm();\n")
 
-  module.append(receiving)
   if settings.SUPPORT_LONGJMP == 'emscripten' or not settings.DISABLE_EXCEPTION_CATCHING:
     module.append(create_invoke_wrappers(metadata))
   else: