emscripten-core · sbc100 · Dec 19, 2024 · Dec 10, 2024
diff --git a/ChangeLog.md b/ChangeLog.md
@@ -33,6 +33,12 @@ See docs/process.md for more on how version tagging works.
   `PATH.basename("a/b/..")` returns `".."` instead of `"a"`. This is in line with
   the behaviour of both node and coreutils, and is already the case when using
   NODERAWFS". (#23180)
+- The factory function exposed in `-sMODULARIZE` mode is now marked as `async`
+  when `WASM_ASYNC_COMPILATION` is enabled (the default). This allows us to use
+  `await` during module creation.  One side effect of this is that code in
+  `--post-js` files will now be delayed until after module creation and after
+  `main` runs.  This matches the existing behaviour when using sync instantation
+  (`-sWASM_ASYNC_COMPILATION=0`) but is an observable difference. (#23157)
 
 3.1.74 - 12/14/24
 -----------------

diff --git a/src/preamble.js b/src/preamble.js
@@ -1036,11 +1036,11 @@ function getWasmImports() {
     trueModule = null;
 #endif
 #if SHARED_MEMORY || RELOCATABLE
-    receiveInstance(result['instance'], result['module']);
+    return receiveInstance(result['instance'], result['module']);
 #else
     // TODO: Due to Closure regression https://github.com/google/closure-compiler/issues/3193, the above line no longer optimizes out down to the following line.
     // When the regression is fixed, can restore the above PTHREADS-enabled path.
-    receiveInstance(result['instance']);
+    return receiveInstance(result['instance']);
 #endif
   }
 #endif // WASM_ASYNC_COMPILATION
@@ -1076,8 +1076,7 @@ function getWasmImports() {
         // Instantiate from the module posted from the main thread.
         // We can just use sync instantiation in the worker.
         var instance = new WebAssembly.Instance(module, getWasmImports());
-        receiveInstance(instance, module);
-        resolve();
+        resolve(receiveInstance(instance, module));
       };
     });
   }
@@ -1095,16 +1094,16 @@ function getWasmImports() {
   try {
 #endif
     var result = await instantiateAsync(wasmBinary, wasmBinaryFile, info);
-    receiveInstantiationResult(result);
+    var exports = receiveInstantiationResult(result);
 #if LOAD_SOURCE_MAP
     receiveSourceMapJSON(await getSourceMapAsync());
 #endif
-    return result;
+    return exports;
 #if MODULARIZE
   } catch (e) {
     // If instantiation fails, reject the module ready promise.
     readyPromiseReject(e);
-    return;
+    return Promise.reject(e);
   }
 #endif
 #else // WASM_ASYNC_COMPILATION

diff --git a/test/browser/test_small_js_flags.js.size b/test/browser/test_small_js_flags.js.size
@@ -1 +1 @@
-4380
+4374
diff --git a/test/code_size/hello_webgl2_wasm.json b/test/code_size/hello_webgl2_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4532,
-  "a.js.gz": 2315,
+  "a.js": 4538,
+  "a.js.gz": 2320,
   "a.wasm": 10402,
   "a.wasm.gz": 6703,
-  "total": 15388,
-  "total_gz": 9346
+  "total": 15394,
+  "total_gz": 9351
 }
diff --git a/test/code_size/hello_webgl2_wasm2js.json b/test/code_size/hello_webgl2_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 22200,
-  "a.js.gz": 11583,
-  "total": 22546,
-  "total_gz": 11845
+  "a.js": 22206,
+  "a.js.gz": 11589,
+  "total": 22552,
+  "total_gz": 11851
 }
diff --git a/test/code_size/hello_webgl_wasm.json b/test/code_size/hello_webgl_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4070,
-  "a.js.gz": 2158,
+  "a.js": 4076,
+  "a.js.gz": 2163,
   "a.wasm": 10402,
   "a.wasm.gz": 6703,
-  "total": 14926,
-  "total_gz": 9189
+  "total": 14932,
+  "total_gz": 9194
 }
diff --git a/test/code_size/hello_webgl_wasm2js.json b/test/code_size/hello_webgl_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 21726,
-  "a.js.gz": 11413,
-  "total": 22072,
-  "total_gz": 11675
+  "a.js": 21732,
+  "a.js.gz": 11419,
+  "total": 22078,
+  "total_gz": 11681
 }
diff --git a/test/other/codesize/test_codesize_cxx_ctors1.gzsize b/test/other/codesize/test_codesize_cxx_ctors1.gzsize
@@ -1 +1 @@
-8352
+8351
diff --git a/test/other/codesize/test_codesize_cxx_ctors1.jssize b/test/other/codesize/test_codesize_cxx_ctors1.jssize
@@ -1 +1 @@
-20347
+20343
diff --git a/test/other/codesize/test_codesize_cxx_ctors2.gzsize b/test/other/codesize/test_codesize_cxx_ctors2.gzsize
@@ -1 +1 @@
-8336
+8334
diff --git a/test/other/codesize/test_codesize_cxx_ctors2.jssize b/test/other/codesize/test_codesize_cxx_ctors2.jssize
@@ -1 +1 @@
-20315
+20311
diff --git a/test/other/codesize/test_codesize_cxx_except.gzsize b/test/other/codesize/test_codesize_cxx_except.gzsize
@@ -1 +1 @@
-9358
+9356
diff --git a/test/other/codesize/test_codesize_cxx_except.jssize b/test/other/codesize/test_codesize_cxx_except.jssize
@@ -1 +1 @@
-24116
+24112
diff --git a/test/other/codesize/test_codesize_cxx_except_wasm.jssize b/test/other/codesize/test_codesize_cxx_except_wasm.jssize
@@ -1 +1 @@
-20240
+20236
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 @@
-20240
+20236
diff --git a/test/other/codesize/test_codesize_cxx_lto.gzsize b/test/other/codesize/test_codesize_cxx_lto.gzsize
@@ -1 +1 @@
-8348
+8347
diff --git a/test/other/codesize/test_codesize_cxx_lto.jssize b/test/other/codesize/test_codesize_cxx_lto.jssize
@@ -1 +1 @@
-20371
+20367
diff --git a/test/other/codesize/test_codesize_cxx_mangle.gzsize b/test/other/codesize/test_codesize_cxx_mangle.gzsize
@@ -1 +1 @@
-9361
+9359
diff --git a/test/other/codesize/test_codesize_cxx_mangle.jssize b/test/other/codesize/test_codesize_cxx_mangle.jssize
@@ -1 +1 @@
-24116
+24112
diff --git a/test/other/codesize/test_codesize_cxx_noexcept.gzsize b/test/other/codesize/test_codesize_cxx_noexcept.gzsize
@@ -1 +1 @@
-8352
+8351
diff --git a/test/other/codesize/test_codesize_cxx_noexcept.jssize b/test/other/codesize/test_codesize_cxx_noexcept.jssize
@@ -1 +1 @@
-20347
+20343
diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.gzsize b/test/other/codesize/test_codesize_cxx_wasmfs.gzsize
@@ -1 +1 @@
-3653
+3651
diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.jssize b/test/other/codesize/test_codesize_cxx_wasmfs.jssize
@@ -1 +1 @@
-7914
+7910
diff --git a/test/other/codesize/test_codesize_files_js_fs.gzsize b/test/other/codesize/test_codesize_files_js_fs.gzsize
@@ -1 +1 @@
-7656
+7654
diff --git a/test/other/codesize/test_codesize_files_js_fs.jssize b/test/other/codesize/test_codesize_files_js_fs.jssize
@@ -1 +1 @@
-18842
+18838
diff --git a/test/other/codesize/test_codesize_files_wasmfs.jssize b/test/other/codesize/test_codesize_files_wasmfs.jssize
@@ -1 +1 @@
-6202
+6198
diff --git a/test/other/codesize/test_codesize_hello_O0.gzsize b/test/other/codesize/test_codesize_hello_O0.gzsize
@@ -1 +1 @@
-8017
+8012
diff --git a/test/other/codesize/test_codesize_hello_O0.jssize b/test/other/codesize/test_codesize_hello_O0.jssize
@@ -1 +1 @@
-21597
+21588
diff --git a/test/other/codesize/test_codesize_hello_O1.gzsize b/test/other/codesize/test_codesize_hello_O1.gzsize
@@ -1 +1 @@
-2697
+2694
diff --git a/test/other/codesize/test_codesize_hello_O1.jssize b/test/other/codesize/test_codesize_hello_O1.jssize
@@ -1 +1 @@
-6911
+6899
diff --git a/test/other/codesize/test_codesize_hello_O2.gzsize b/test/other/codesize/test_codesize_hello_O2.gzsize
@@ -1 +1 @@
-2359
+2357
diff --git a/test/other/codesize/test_codesize_hello_O2.jssize b/test/other/codesize/test_codesize_hello_O2.jssize
@@ -1 +1 @@
-4835
+4831
diff --git a/test/other/codesize/test_codesize_hello_O3.gzsize b/test/other/codesize/test_codesize_hello_O3.gzsize
@@ -1 +1 @@
-2298
+2296
diff --git a/test/other/codesize/test_codesize_hello_O3.jssize b/test/other/codesize/test_codesize_hello_O3.jssize
@@ -1 +1 @@
-4757
+4753
diff --git a/test/other/codesize/test_codesize_hello_Os.gzsize b/test/other/codesize/test_codesize_hello_Os.gzsize
@@ -1 +1 @@
-2298
+2296
diff --git a/test/other/codesize/test_codesize_hello_Os.jssize b/test/other/codesize/test_codesize_hello_Os.jssize
@@ -1 +1 @@
-4757
+4753
diff --git a/test/other/codesize/test_codesize_hello_Oz.gzsize b/test/other/codesize/test_codesize_hello_Oz.gzsize
@@ -1 +1 @@
-2281
+2279
diff --git a/test/other/codesize/test_codesize_hello_Oz.jssize b/test/other/codesize/test_codesize_hello_Oz.jssize
@@ -1 +1 @@
-4724
+4720
diff --git a/test/other/codesize/test_codesize_hello_dylink.gzsize b/test/other/codesize/test_codesize_hello_dylink.gzsize
@@ -1 +1 @@
-6023
+6028
diff --git a/test/other/codesize/test_codesize_hello_dylink.jssize b/test/other/codesize/test_codesize_hello_dylink.jssize
@@ -1 +1 @@
-13300
+13317
diff --git a/test/other/codesize/test_codesize_hello_export_nothing.gzsize b/test/other/codesize/test_codesize_hello_export_nothing.gzsize
@@ -1 +1 @@
-1682
+1681
diff --git a/test/other/codesize/test_codesize_hello_export_nothing.jssize b/test/other/codesize/test_codesize_hello_export_nothing.jssize
@@ -1 +1 @@
-3637
+3633
diff --git a/test/other/codesize/test_codesize_hello_wasmfs.gzsize b/test/other/codesize/test_codesize_hello_wasmfs.gzsize
@@ -1 +1 @@
-2298
+2296
diff --git a/test/other/codesize/test_codesize_hello_wasmfs.jssize b/test/other/codesize/test_codesize_hello_wasmfs.jssize
@@ -1 +1 @@
-4757
+4753
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize b/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize
@@ -1 +1 @@
-1876
+1873
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize b/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize
@@ -1 +1 @@
-4000
+3996
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 @@
-1914
+1912
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 @@
-4048
+4044
diff --git a/test/other/codesize/test_codesize_mem_O3.gzsize b/test/other/codesize/test_codesize_mem_O3.gzsize
@@ -1 +1 @@
-2328
+2327
diff --git a/test/other/codesize/test_codesize_mem_O3.jssize b/test/other/codesize/test_codesize_mem_O3.jssize
@@ -1 +1 @@
-4892
+4888
diff --git a/test/other/codesize/test_codesize_mem_O3_grow.gzsize b/test/other/codesize/test_codesize_mem_O3_grow.gzsize
@@ -1 +1 @@
-2478
+2476
diff --git a/test/other/codesize/test_codesize_mem_O3_grow.jssize b/test/other/codesize/test_codesize_mem_O3_grow.jssize
@@ -1 +1 @@
-5177
+5172
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 @@
-2180
+2177
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 @@
-4585
+4581
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone.gzsize
@@ -1 +1 @@
-2143
+2140
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.jssize b/test/other/codesize/test_codesize_mem_O3_standalone.jssize
@@ -1 +1 @@
-4517
+4513
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 @@
-1900
+1898
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 @@
-4047
+4043
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 @@
-1914
+1912
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 @@
-4048
+4044
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 @@
-1914
+1912
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 @@
-4048
+4044
diff --git a/test/other/codesize/test_codesize_minimal_64.gzsize b/test/other/codesize/test_codesize_minimal_64.gzsize
@@ -1 +1 @@
-1439
+1441
diff --git a/test/other/codesize/test_codesize_minimal_64.jssize b/test/other/codesize/test_codesize_minimal_64.jssize
@@ -1 +1 @@
-3064
+3058
diff --git a/test/other/codesize/test_codesize_minimal_O1.gzsize b/test/other/codesize/test_codesize_minimal_O1.gzsize
@@ -1 +1 @@
-1531
+1534
diff --git a/test/other/codesize/test_codesize_minimal_O1.jssize b/test/other/codesize/test_codesize_minimal_O1.jssize
@@ -1 +1 @@
-3713
+3702
diff --git a/test/other/codesize/test_codesize_minimal_O2.gzsize b/test/other/codesize/test_codesize_minimal_O2.gzsize
@@ -1 +1 @@
-1380
+1381
diff --git a/test/other/codesize/test_codesize_minimal_O2.jssize b/test/other/codesize/test_codesize_minimal_O2.jssize
@@ -1 +1 @@
-2812
+2806
diff --git a/test/other/codesize/test_codesize_minimal_O3.gzsize b/test/other/codesize/test_codesize_minimal_O3.gzsize
@@ -1 +1 @@
-1346
+1348
diff --git a/test/other/codesize/test_codesize_minimal_O3.jssize b/test/other/codesize/test_codesize_minimal_O3.jssize
@@ -1 +1 @@
-2762
+2756
diff --git a/test/other/codesize/test_codesize_minimal_Os.gzsize b/test/other/codesize/test_codesize_minimal_Os.gzsize
@@ -1 +1 @@
-1346
+1348
diff --git a/test/other/codesize/test_codesize_minimal_Os.jssize b/test/other/codesize/test_codesize_minimal_Os.jssize
@@ -1 +1 @@
-2762
+2756
diff --git a/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize b/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize
@@ -1 +1 @@
-2747
+2741
diff --git a/test/other/codesize/test_codesize_minimal_Oz.gzsize b/test/other/codesize/test_codesize_minimal_Oz.gzsize
@@ -1 +1 @@
-1346
+1348
diff --git a/test/other/codesize/test_codesize_minimal_Oz.jssize b/test/other/codesize/test_codesize_minimal_Oz.jssize
@@ -1 +1 @@
-2762
+2756
diff --git a/test/other/codesize/test_codesize_minimal_esm.gzsize b/test/other/codesize/test_codesize_minimal_esm.gzsize
@@ -1 +1 @@
-1496
+1509
diff --git a/test/other/codesize/test_codesize_minimal_esm.jssize b/test/other/codesize/test_codesize_minimal_esm.jssize
@@ -1 +1 @@
-3138
+3157
diff --git a/test/other/codesize/test_codesize_minimal_pthreads.gzsize b/test/other/codesize/test_codesize_minimal_pthreads.gzsize
@@ -1 +1 @@
-4184
+4190
diff --git a/test/other/codesize/test_codesize_minimal_pthreads.jssize b/test/other/codesize/test_codesize_minimal_pthreads.jssize
@@ -1 +1 @@
-8711
+8728
diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.gzsize b/test/other/codesize/test_codesize_minimal_wasmfs.gzsize
@@ -1 +1 @@
-1346
+1348
diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.jssize b/test/other/codesize/test_codesize_minimal_wasmfs.jssize
@@ -1 +1 @@
-2762
+2756
diff --git a/test/other/test_INCOMING_MODULE_JS_API.js.size b/test/other/test_INCOMING_MODULE_JS_API.js.size
@@ -1 +1 @@
-3772
+3766
diff --git a/test/other/test_unoptimized_code_size.js.size b/test/other/test_unoptimized_code_size.js.size
@@ -1 +1 @@
-53866
+53888
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 @@
-29065
+29087
diff --git a/test/other/test_unoptimized_code_size_strict.js.size b/test/other/test_unoptimized_code_size_strict.js.size
@@ -1 +1 @@
-52649
+52671
diff --git a/test/test_unicode_js_library.out b/test/test_unicode_js_library.out
@@ -1,2 +1,2 @@
-Unicode postjs: àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
 Unicode snowman ☃ says hello! àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
+Unicode postjs: àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
diff --git a/tools/emscripten.py b/tools/emscripten.py
@@ -893,6 +893,16 @@ def create_sending(metadata, library_symbols):
   return '{\n  ' + ',\n  '.join(elems) + '\n}'
 
 
+def can_use_await():
+  # In MODULARIZE mode we can use `await` since the factory function itself
+  # is marked as `async` and the generated code all lives inside that factory
+  # function.
+  # However, because closure does not see this (it runs only on the inner code),
+  # it sees this as a top-level-await, which it does not yet support.
+  # FIXME(https://github.com/emscripten-core/emscripten/issues/23158)
+  return settings.MODULARIZE and not settings.USE_CLOSURE_COMPILER
+
+
 def make_export_wrappers(function_exports):
   assert not settings.MINIMAL_RUNTIME
 
@@ -932,7 +942,7 @@ def install_wrapper(sym):
       # 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 or settings.PTHREADS:
+    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)]
@@ -998,7 +1008,11 @@ def create_module(receiving, metadata, global_exports, library_symbols):
 
   if not settings.MINIMAL_RUNTIME:
     if settings.WASM_ASYNC_COMPILATION:
-      module.append("var wasmExports;\ncreateWasm();\n")
+      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")
     else:
       module.append("var wasmExports = createWasm();\n")