Add list of JS-only settings

ChangeLog.md

@@ -20,6 +20,8 @@ See docs/process.md for more on how version tagging works.
 
 3.1.52 (in development)
 -----------------------
+- Certain settings that only apply when generating JavaScript output will now
+  trigger a warning if used when generating only Wasm.
 - Fix bug where `main` was mistakenly included in debug builds but not in
   release builds. (#20971)
 - Remove JAVA from the list of `.emscripten` config file settings.  In the

test/test_other.py

@@ -14414,3 +14414,7 @@ def test_no_extra_output(self):
   def test_browser_too_old(self):
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sMIN_CHROME_VERSION=10'])
     self.assertContained('emcc: error: MIN_CHROME_VERSION older than 32 is not supported', err)
+
+  def test_js_only_settings(self):
+    err = self.run_process([EMCC, test_file('hello_world.c'), '-o', 'foo.wasm', '-sDEFAULT_LIBRARY_FUNCS_TO_INCLUDE=emscripten_get_heap_max'], stderr=PIPE).stderr
+    self.assertContained('emcc: warning: DEFAULT_LIBRARY_FUNCS_TO_INCLUDE is only valid when generated JavaScript output', err)

tools/link.py

@@ -38,7 +38,7 @@
 from .shared import in_temp, safe_copy, do_replace, run_process, OFormat
 from .shared import DEBUG, WINDOWS, DYNAMICLIB_ENDINGS, STATICLIB_ENDINGS
 from .shared import unsuffixed, unsuffixed_basename, get_file_suffix
-from .settings import settings, default_setting, user_settings
+from .settings import settings, default_setting, user_settings, JS_ONLY_SETTINGS
 from .minimal_runtime_shell import generate_minimal_runtime_html
 
 import tools.line_endings
@@ -753,6 +753,11 @@ def phase_linker_setup(options, state, newargs):
     else:
       options.oformat = OFormat.JS
 
+  if options.oformat in (OFormat.WASM, OFormat.OBJECT):
+    for s in JS_ONLY_SETTINGS:
+      if s in user_settings:
+        diagnostics.warning('unused-command-line-argument', f'{s} is only valid when generated JavaScript output')
+
   if options.oformat == OFormat.MJS:
     settings.EXPORT_ES6 = 1
     settings.MODULARIZE = 1

tools/settings.py

@@ -54,6 +54,27 @@
     'USE_SQLITE3',
 }
 
+# Subset of settings that apply only when generating JS
+JS_ONLY_SETTINGS = {
+    'DEFAULT_LIBRARY_FUNCS_TO_INCLUDE',
+    'INCLUDE_FULL_LIBRARY',
+    'PROXY_TO_WORKER',
+    'PROXY_TO_WORKER_FILENAME',
+    'BUILD_AS_WORKER',
+    'STRICT_JS',
+    'SMALL_XHR_CHUNKS',
+    'HEADLESS',
+    'MODULARIZE',
+    'EXPORT_ES6',
+    'USE_ES6_IMPORT_META',
+    'EXPORT_NAME',
+    'DYNAMIC_EXECUTION',
+    'PTHREAD_POOL_SIZE',
+    'PTHREAD_POOL_SIZE_STRICT',
+    'PTHREAD_POOL_DELAY_LOAD',
+    'DEFAULT_PTHREAD_STACK_SIZE',
+}
+
 # Subset of settings that apply at compile time.
 # (Keep in sync with [compile] comments in settings.js)
 COMPILE_TIME_SETTINGS = {