[wasm-esm-integration] Fix EMSCRIPETEN_KEEPALIVE (#24108)

As part of this change we re-export all wasm symbols from the support JS
file. Going forward this also means we can support things like JS
wrappers.

Fixes: #24083

Author: sbc100

test/core/test_esm_integration.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <emscripten.h>
+
+EMSCRIPTEN_KEEPALIVE void foo() {
+  printf("foo called\n");
+}
+
+int main(int argc, char* argv[]) {
+  printf("hello, world! (%d)\n", argc);
+  return 0;
+}

test/core/test_esm_integration.expected.mjs

@@ -1,2 +1,4 @@
-export { __main_argc_argv as main } from './hello_world.wasm';
-export { default, err, stringToNewUTF8 } from './hello_world.support.mjs';
+// The wasm module must be imported here first before the support file
+// in order to avoid issues with circular dependencies.
+import * as unused from './hello_world.wasm';
+export { default, _foo, _main, err, stringToNewUTF8 } from './hello_world.support.mjs';

test/test_core.py

@@ -9568,9 +9568,9 @@ def test_esm_integration(self):
     # TODO(sbc): WASM_ESM_INTEGRATION doesn't currently work with closure.
     # self.maybe_closure()
     self.node_args += ['--experimental-wasm-modules', '--no-warnings']
-    self.run_process([EMCC, '-o', 'hello_world.mjs', '-sEXPORTED_RUNTIME_METHODS=err', '-sEXPORTED_FUNCTIONS=_main,stringToNewUTF8', '-sWASM_ESM_INTEGRATION', '-Wno-experimental', test_file('hello_world_argv.c')] + self.get_emcc_args())
+    self.run_process([EMCC, '-o', 'hello_world.mjs', '-sEXPORTED_RUNTIME_METHODS=err', '-sEXPORTED_FUNCTIONS=_main,stringToNewUTF8', '-sWASM_ESM_INTEGRATION', '-Wno-experimental', test_file('core/test_esm_integration.c')] + self.get_emcc_args())
     create_file('runner.mjs', '''
-      import init, { err, stringToNewUTF8, main } from "./hello_world.mjs";
+      import init, { err, stringToNewUTF8, _main, _foo } from "./hello_world.mjs";
       await init({arguments: ['foo', 'bar']});
       err('this is a pointer:', stringToNewUTF8('hello'));
     ''')

tools/emscripten.py

@@ -433,7 +433,8 @@ def emscript(in_wasm, out_wasm, outfile_js, js_syms, finalize=True, base_metadat
   receiving = create_receiving(function_exports)
   if settings.WASM_ESM_INTEGRATION:
     sending = create_sending(metadata, forwarded_json['librarySymbols'])
-    parts += [sending, receiving]
+    reexports = create_reexports()
+    parts += [sending, receiving, reexports]
   else:
     parts += create_module(receiving, metadata, global_exports, forwarded_json['librarySymbols'])
   parts.append(post)
@@ -858,7 +859,10 @@ def create_sending(metadata, library_symbols):
     elems = []
     for k, v in sorted_items:
       elems.append(f'{v} as {k}')
-    return f"export {{ {', '.join(elems)} }};\n\n"
+    elems = ',\n  '.join(elems)
+    exports = '// Export JS functions to the wasm module with demangled names.\n'
+    exports += f"export {{\n  {elems}\n}};\n\n"
+    return exports
 
   prefix = ''
   if settings.MAYBE_CLOSURE_COMPILER:
@@ -876,6 +880,21 @@ def create_sending(metadata, library_symbols):
   return '{\n  ' + ',\n  '.join(elems) + '\n}'
 
 
+def create_reexports():
+  assert settings.WASM_ESM_INTEGRATION
+  exports = '// Re-export imported wasm functions to the JS entry point. These are user-facing and underscore mangled.\n'
+  wasm_exports = []
+  for exp in building.user_requested_exports:
+    if shared.is_c_symbol(exp):
+      demangled = shared.demangle_c_symbol_name(exp)
+      if demangled in settings.WASM_EXPORTS:
+        wasm_exports.append(exp)
+      if demangled == 'main' and '__main_argc_argv' in settings.WASM_EXPORTS:
+        wasm_exports.append('_main')
+  exports += f"export {{ {', '.join(wasm_exports)} }};\n\n"
+  return exports
+
+
 def can_use_await():
   return settings.MODULARIZE
 

tools/link.py

@@ -2116,28 +2116,13 @@ def create_worker_file(input_file, target_dir, output_file, options):
 
 
 def create_esm_wrapper(wrapper_file, support_target, wasm_target):
-  wasm_exports = []
-  js_exports = list(settings.EXPORTED_RUNTIME_METHODS)
-  for f in settings.USER_EXPORTS:
-    if f == '_main' and '__main_argc_argv' in settings.WASM_EXPORTS:
-      wasm_exports.append('__main_argc_argv as main')
-    elif f in settings.WASM_EXPORTS:
-      wasm_exports.append(shared.demangle_c_symbol_name(f))
-    else:
-      js_exports.append(f)
-  wasm_exports = ', '.join(wasm_exports)
-  js_exports = ', '.join(js_exports)
+  js_exports = settings.EXPORTED_RUNTIME_METHODS + list(building.user_requested_exports)
+  js_exports = ', '.join(sorted(js_exports))
 
   wrapper = []
-  if wasm_exports:
-    wrapper.append(f"export {{ {wasm_exports} }} from './{settings.WASM_BINARY_FILE}';")
-    # Because of the wasm ESM integration worker we need to make sure we import
-    # the wasm module here, before we import the support.js file.
-    # So, if there are no other exports we at least export the `memory`.
-  else:
-    wrapper.append('// The wasm module must be imported here first before the support file')
-    wrapper.append('// in order to avoid issues with circullr dependencies.')
-    wrapper.append(f"import * as unused from './{settings.WASM_BINARY_FILE}';")
+  wrapper.append('// The wasm module must be imported here first before the support file')
+  wrapper.append('// in order to avoid issues with circular dependencies.')
+  wrapper.append(f"import * as unused from './{settings.WASM_BINARY_FILE}';")
   support_url = f'./{os.path.basename(support_target)}'
   if js_exports:
     wrapper.append(f"export {{ default, {js_exports} }} from '{support_url}';")