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 · 5ca2258 · 5ca2258
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diff --git a/ChangeLog.md b/ChangeLog.md
@@ -23,6 +23,8 @@ See docs/process.md for more on how version tagging works.
 - The minimum version of node required to run emscripten was bumped from v16.20
   to v18.  Version 4.0 was mistakenly shipped with a change that required v20,
   but that was reverted. (#23410)
+- Taking a refernce to an exported function before the Wasm module is loaded,
+  and then calling its later, is no longer supported. (#23411)
 
 4.0.0 - 01/14/25
 ----------------

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
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diff --git a/test/other/codesize/test_codesize_cxx_noexcept.gzsize b/test/other/codesize/test_codesize_cxx_noexcept.gzsize
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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
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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
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diff --git a/test/other/codesize/test_codesize_files_wasmfs.gzsize b/test/other/codesize/test_codesize_files_wasmfs.gzsize
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diff --git a/test/other/codesize/test_codesize_files_wasmfs.jssize b/test/other/codesize/test_codesize_files_wasmfs.jssize
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diff --git a/test/other/codesize/test_codesize_hello_O0.gzsize b/test/other/codesize/test_codesize_hello_O0.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_O2.gzsize b/test/other/codesize/test_codesize_hello_O2.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_O2.jssize b/test/other/codesize/test_codesize_hello_O2.jssize
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diff --git a/test/other/codesize/test_codesize_hello_O3.gzsize b/test/other/codesize/test_codesize_hello_O3.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_O3.jssize b/test/other/codesize/test_codesize_hello_O3.jssize
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diff --git a/test/other/codesize/test_codesize_hello_Os.gzsize b/test/other/codesize/test_codesize_hello_Os.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_Os.jssize b/test/other/codesize/test_codesize_hello_Os.jssize
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diff --git a/test/other/codesize/test_codesize_hello_Oz.gzsize b/test/other/codesize/test_codesize_hello_Oz.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_Oz.jssize b/test/other/codesize/test_codesize_hello_Oz.jssize
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diff --git a/test/other/codesize/test_codesize_hello_dylink.gzsize b/test/other/codesize/test_codesize_hello_dylink.gzsize
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diff --git a/test/other/codesize/test_codesize_hello_wasmfs.gzsize b/test/other/codesize/test_codesize_hello_wasmfs.gzsize
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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
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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
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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
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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
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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
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