Set INCOMING_MODULE_JS_API to empty in STRICT mode (emscripten-core#1…

…6372)

In strict mode, make this list empty default which saves on code size
and complexity.  In this mode one needs to opt into any incoming module
symbols you want to use.

ChangeLog.md

@@ -24,6 +24,12 @@ See docs/process.md for more on how version tagging works.
 - The `--minify=0` commnad line flag will now preserve comments as well as
   whitespace.  This means the resulting output can then be run though closure
   compiler or some other tool that gives comments semantic meaning. (#20121)
+- `-sSTRICT` now implies `-sINCOMING_MODULE_API=[]` which is generally good
+  for code size.  If you `-sSTRICT` you now need to be explicit about the
+  incoming module APIs you are supplying.  Users who supply symbols on the
+  incoming module but forget to include them in `-sINCOMING_MODULE_API`
+  will see an error in debug builds so this change will not generate any
+  silent failures.
 
 3.1.45 - 08/23/23
 -----------------

emcc.py

@@ -75,6 +75,7 @@
 STATICLIB_ENDINGS = ['.a']
 ASSEMBLY_ENDINGS = ['.s']
 HEADER_ENDINGS = ['.h', '.hxx', '.hpp', '.hh', '.H', '.HXX', '.HPP', '.HH']
+DEFAULT_SHELL_HTML = utils.path_from_root('src/shell.html')
 
 # Supported LLD flags which we will pass through to the linker.
 SUPPORTED_LINKER_FLAGS = (
@@ -268,7 +269,7 @@ def __init__(self):
     self.embed_files = []
     self.exclude_files = []
     self.ignore_dynamic_linking = False
-    self.shell_path = utils.path_from_root('src/shell.html')
+    self.shell_path = DEFAULT_SHELL_HTML
     self.source_map_base = ''
     self.embind_emit_tsd = ''
     self.emrun = False
@@ -2041,6 +2042,11 @@ def phase_linker_setup(options, state, newargs):
     default_setting('AUTO_ARCHIVE_INDEXES', 0)
     default_setting('IGNORE_MISSING_MAIN', 0)
     default_setting('ALLOW_UNIMPLEMENTED_SYSCALLS', 0)
+    if options.oformat == OFormat.HTML and options.shell_path == DEFAULT_SHELL_HTML:
+      # Out default shell.html file has minimal set of INCOMING_MODULE_JS_API elements that it expects
+      default_setting('INCOMING_MODULE_JS_API', 'canvas,monitorRunDependencies,onAbort,onExit,print,setStatus'.split(','))
+    else:
+      default_setting('INCOMING_MODULE_JS_API', [])
 
   if 'GLOBAL_BASE' not in user_settings and not settings.SHRINK_LEVEL and not settings.OPT_LEVEL:
     # When optimizing for size it helps to put static data first before
@@ -2602,7 +2608,7 @@ def check_memory_setting(setting):
 
   if settings.MINIMAL_RUNTIME:
     # Minimal runtime uses a different default shell file
-    if options.shell_path == utils.path_from_root('src/shell.html'):
+    if options.shell_path == DEFAULT_SHELL_HTML:
       options.shell_path = utils.path_from_root('src/shell_minimal_runtime.html')
 
     if settings.ASSERTIONS:
@@ -2614,7 +2620,7 @@ def check_memory_setting(setting):
 
   if settings.MODULARIZE and not (settings.EXPORT_ES6 and not settings.SINGLE_FILE) and \
      settings.EXPORT_NAME == 'Module' and options.oformat == OFormat.HTML and \
-     (options.shell_path == utils.path_from_root('src/shell.html') or options.shell_path == utils.path_from_root('src/shell_minimal.html')):
+     (options.shell_path == DEFAULT_SHELL_HTML or options.shell_path == utils.path_from_root('src/shell_minimal.html')):
     exit_with_error(f'Due to collision in variable name "Module", the shell file "{options.shell_path}" is not compatible with build options "-sMODULARIZE -sEXPORT_NAME=Module". Either provide your own shell file, change the name of the export to something else to avoid the name collision. (see https://github.com/emscripten-core/emscripten/issues/7950 for details)')
 
   # TODO(sbc): Remove WASM2JS here once the size regression it would introduce has been fixed.
@@ -4154,7 +4160,7 @@ def generate_html(target, options, js_target, target_basename,
 
   if settings.EXPORT_NAME != 'Module' and \
      not settings.MINIMAL_RUNTIME and \
-     options.shell_path == utils.path_from_root('src/shell.html'):
+     options.shell_path == DEFAULT_SHELL_HTML:
     # the minimal runtime shell HTML is designed to support changing the export
     # name, but the normal one does not support that currently
     exit_with_error('Customizing EXPORT_NAME requires that the HTML be customized to use that name (see https://github.com/emscripten-core/emscripten/issues/10086)')

site/source/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.rst

@@ -755,7 +755,7 @@ For example, to set an environment variable ``MY_FILE_ROOT`` to be
 
 .. code:: javascript
 
-    Module.preRun.push(function() {ENV.MY_FILE_ROOT = "/usr/lib/test"})
+    Module.preRun = () => {ENV.MY_FILE_ROOT = "/usr/lib/test"};
 
 Note that Emscripten will set default values for some environment variables
 (e.g. LANG) after you have configured ``ENV``, if you have not set your own
@@ -764,7 +764,7 @@ their value to `undefined`. For example:
 
 .. code:: javascript
 
-    Module.preRun.push(function() {ENV.LANG = undefined})
+    Module.preRun = () => {ENV.LANG = undefined};
 
 .. _interacting-with-code-binding-cpp:
 

src/settings.js

@@ -1116,6 +1116,7 @@ var LINKABLE = false;
 //   * DEFAULT_TO_CXX is disabled.
 //   * USE_GLFW is set to 0 rather than 2 by default.
 //   * ALLOW_UNIMPLEMENTED_SYSCALLS is disabled.
+//   * INCOMING_MODULE_JS_API is set to empty by default.
 // [compile+link]
 var STRICT = false;
 

src/shell.html

@@ -1222,8 +1222,6 @@
       var spinnerElement = document.getElementById('spinner');
 
       var Module = {
-        preRun: [],
-        postRun: [],
         print: (function() {
           var element = document.getElementById('output');
           if (element) element.value = ''; // clear browser cache

src/shell_minimal.html

@@ -74,8 +74,6 @@
       var spinnerElement = document.getElementById('spinner');
 
       var Module = {
-        preRun: [],
-        postRun: [],
         print: (function() {
           var element = document.getElementById('output');
           if (element) element.value = ''; // clear browser cache

test/browser/cwrap_early.js

@@ -1,5 +1,4 @@
-
-Module['preRun'].push(function() {
+Module['preRun'] = () => {
   console.log('preRun');
   // it is ok to call cwrap before the runtime is loaded. we don't need the code
   // and everything to be ready, since cwrap just prepares to call code, it 
@@ -15,6 +14,4 @@ Module['preRun'].push(function() {
     xhr.send();
     setTimeout(function() { window.close() }, 1000);
   };
-});
-
-
+};

test/test_browser.py

@@ -2241,9 +2241,9 @@ def test_sdl_gfx_primitives(self):
 
   def test_sdl_canvas_palette_2(self):
     create_file('pre.js', '''
-      Module['preRun'].push(function() {
+      Module['preRun'] = () => {
         SDL.defaults.copyOnLock = false;
-      });
+      };
     ''')
 
     create_file('args-r.js', '''
@@ -2525,11 +2525,11 @@ def test_runtime_misuse(self, mode):
       create_file('post.js', post_prep + post_test + post_hook)
       self.btest(filename, expected='600', args=['--post-js', 'post.js', '-sEXIT_RUNTIME'] + extra_args + mode, reporting=Reporting.NONE)
       print('sync startup, call too late')
-      create_file('post.js', post_prep + 'Module.postRun.push(function() { ' + post_test + ' });' + post_hook)
+      create_file('post.js', post_prep + 'Module.postRun = () => { ' + post_test + ' };' + post_hook)
       self.btest(filename, expected=str(second_code), args=['--post-js', 'post.js', '-sEXIT_RUNTIME'] + extra_args + mode, reporting=Reporting.NONE)
 
       print('sync, runtime still alive, so all good')
-      create_file('post.js', post_prep + 'expected_ok = true; Module.postRun.push(function() { ' + post_test + ' });' + post_hook)
+      create_file('post.js', post_prep + 'expected_ok = true; Module.postRun = () => { ' + post_test + ' };' + post_hook)
       self.btest(filename, expected='606', args=['--post-js', 'post.js'] + extra_args + mode, reporting=Reporting.NONE)
 
   def test_cwrap_early(self):
@@ -2644,11 +2644,10 @@ def test_glew(self):
 
   def test_doublestart_bug(self):
     create_file('pre.js', r'''
-if (!Module['preRun']) Module['preRun'] = [];
-Module["preRun"].push(function () {
+Module["preRun"] = () => {
   addRunDependency('test_run_dependency');
   removeRunDependency('test_run_dependency');
-});
+};
 ''')
 
     self.btest('doublestart.c', args=['--pre-js', 'pre.js'], expected='1')

test/test_other.py

@@ -4030,17 +4030,16 @@ def test_doublestart_bug(self):
 ''')
 
     create_file('pre.js', r'''
-if (!Module['preRun']) Module['preRun'] = [];
-Module["preRun"].push(function () {
-    addRunDependency('test_run_dependency');
-    removeRunDependency('test_run_dependency');
-});
+Module["preRun"] = () => {
+  addRunDependency('test_run_dependency');
+  removeRunDependency('test_run_dependency');
+};
 ''')
 
     self.run_process([EMCC, 'code.c', '--pre-js', 'pre.js'])
     output = self.run_js('a.out.js')
 
-    assert output.count('This should only appear once.') == 1, output
+    self.assertEqual(output.count('This should only appear once.'), 1)
 
   def test_module_print(self):
     create_file('code.c', r'''