Error out on missing EXPORTED_RUNTIME_METHODS.

Author: brendandahl

Diff for: ChangeLog.md

@@ -40,6 +40,7 @@ See docs/process.md for more on how version tagging works.
   example, `-sEXPORTED_RUNTIME_METHODS=HEAP8,HEAPU32` (if you need `HEAP8` and
   `HEAPU32`). (#24079)
 - libjpeg port updated from 9c to 9f. (#24085)
+- Missing exports in EXPORTED_RUNTIME_METHODS will now error instead of warn.
 
 4.0.6 - 03/26/25
 ----------------

Diff for: src/modules.mjs

@@ -13,7 +13,6 @@ import {
   isJsOnlySymbol,
   error,
   readFile,
-  warn,
   pushCurrentFile,
   popCurrentFile,
   printErr,
@@ -512,11 +511,11 @@ function exportRuntimeSymbols() {
     }
   }
 
-  // check all exported things exist, warn about typos
+  // check all exported things exist, error when missing
   runtimeElementsSet = new Set(runtimeElements);
   for (const name of EXPORTED_RUNTIME_METHODS) {
     if (!runtimeElementsSet.has(name)) {
-      warn(`invalid item in EXPORTED_RUNTIME_METHODS: ${name}`);
+      error(`undefined exported symbol: "${name}" in EXPORTED_RUNTIME_METHODS`);
     }
   }
 

Diff for: test/test_other.py

@@ -2708,6 +2708,11 @@ def test_undefined_exported_function(self, outfile):
     cmd += ['-Wno-undefined']
     self.run_process(cmd)
 
+  def test_undefined_exported_runtime_method(self):
+    # Adding a missing symbol to EXPORTED_RUNTIME_METHODS should cause a failure
+    err = self.expect_fail([EMCC, '-sEXPORTED_RUNTIME_METHODS=foobar', test_file('hello_world.c')])
+    self.assertContained('undefined exported symbol: "foobar" in EXPORTED_RUNTIME_METHODS', err)
+
   @parameterized({
     '': ('out.js',),
     'standalone': ('out.wasm',)
@@ -14424,7 +14429,7 @@ def test_legacy_runtime(self):
     self.clear_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE')
     for opt in ('-O0', '-O3'):
       err = self.expect_fail([EMCC, test_file('other/test_legacy_runtime.c'), opt] + self.get_emcc_args())
-      self.assertContained('invalid item in EXPORTED_RUNTIME_METHODS: allocate', err)
+      self.assertContained('undefined exported symbol: "allocate" in EXPORTED_RUNTIME_METHODS', err)
 
   def test_fetch_settings(self):
     create_file('pre.js', '''