In EMSCRIPTEN_STRICT mode, stop autolinking to all system provided JS libraries, but instead require explicitly specifying which ones to link to on command line.

Author: juj

emcc.py

@@ -922,6 +922,8 @@ def detect_fixed_language_mode(args):
       if separate_asm:
         shared.Settings.SEPARATE_ASM = os.path.basename(asm_target)
 
+      system_js_libraries = []
+
       # Find library files
       for i, lib in libs:
         logging.debug('looking for library "%s"', lib)
@@ -938,14 +940,39 @@ def detect_fixed_language_mode(args):
                 break
             if found: break
           if found: break
-        if not found and lib not in ['GL', 'GLU', 'glut', 'm', 'c', 'SDL', 'stdc++', 'pthread']: # whitelist our default libraries
-          emscripten_strict_mode = (os.environ.get('EMSCRIPTEN_STRICT') and int(os.environ.get('EMSCRIPTEN_STRICT')) != 0) or 'EMSCRIPTEN_STRICT=1' in settings_changes
-          error_on_missing_libraries = (emscripten_strict_mode and not 'ERROR_ON_MISSING_LIBRARIES=0' in settings_changes) or 'ERROR_ON_MISSING_LIBRARIES=1' in settings_changes
-          if error_on_missing_libraries:
-            logging.fatal('emcc: cannot find library "%s"', lib)
-            exit(1)
+        if not found:
+          # Some native libraries are implemented in Emscripten as system side JS libraries
+          js_system_libraries = {
+            'c': '',
+            'EGL': 'library_egl.js',
+            'GL': 'library_gl.js',
+            'GLESv2': 'library_gl.js',
+            'GLEW': 'library_glew.js',
+            'glfw': 'library_glfw.js',
+            'glfw3': 'library_glfw.js',
+            'GLU': '',
+            'glut': 'library_glut.js',
+            'm': '',
+            'openal': 'library_openal.js',
+            'pthread': '',
+            'SDL': 'library_sdl.js',
+            'stdc++': ''
+          }
+          if lib in js_system_libraries:
+            if len(js_system_libraries[lib]) > 0:
+              system_js_libraries += [js_system_libraries[lib]]
+          elif lib.endswith('.js') and os.path.isfile(shared.path_from_root('src', 'library_' + lib)):
+            system_js_libraries += ['library_' + lib]
           else:
-            logging.warning('emcc: cannot find library "%s"', lib)
+            emscripten_strict_mode = (os.environ.get('EMSCRIPTEN_STRICT') and int(os.environ.get('EMSCRIPTEN_STRICT')) != 0) or 'EMSCRIPTEN_STRICT=1' in settings_changes
+            error_on_missing_libraries = (emscripten_strict_mode and not 'ERROR_ON_MISSING_LIBRARIES=0' in settings_changes) or 'ERROR_ON_MISSING_LIBRARIES=1' in settings_changes
+            if error_on_missing_libraries:
+              logging.fatal('emcc: cannot find library "%s"', lib)
+              exit(1)
+            else:
+              logging.warning('emcc: cannot find library "%s"', lib)
+
+      settings_changes.append('SYSTEM_JS_LIBRARIES="' + ','.join(system_js_libraries) + '"')
 
       # If not compiling to JS, then we are compiling to an intermediate bitcode objects or library, so
       # ignore dynamic linking, since multiple dynamic linkings can interfere with each other

src/modules.js

@@ -96,41 +96,62 @@ var LibraryManager = {
   load: function() {
     if (this.library) return;
 
+    // Core system libraries (always linked against)
     var libraries = [
       'library.js',
       'library_browser.js',
       'library_formatString.js',
       'library_path.js',
-      'library_syscall.js'
+      'library_syscall.js',
+      'library_html5.js'
     ];
+
     if (!NO_FILESYSTEM) {
+      // Core filesystem libraries (always linked against, unless -s NO_FILESYSTEM=1 is specified)
       libraries = libraries.concat([
         'library_fs.js',
-        'library_idbfs.js',
         'library_memfs.js',
-        'library_nodefs.js',
-        'library_sockfs.js',
-        'library_workerfs.js',
         'library_tty.js',
-        'library_lz4.js',
+      ]);
+
+      // Additional filesystem libraries (in strict mode, link to these explicitly via -lxxx.js)
+      if (!EMSCRIPTEN_STRICT) {
+        libraries = libraries.concat([
+          'library_idbfs.js',
+          'library_nodefs.js',
+          'library_sockfs.js',
+          'library_workerfs.js',
+          'library_lz4.js',
+        ]);
+      }
+    }
+
+    // Additional JS libraries (in strict mode, link to these explicitly via -lxxx.js)
+    if (!EMSCRIPTEN_STRICT) {
+      libraries = libraries.concat([
+        'library_sdl.js',
+        'library_gl.js',
+        'library_glut.js',
+        'library_xlib.js',
+        'library_egl.js',
+        'library_openal.js',
+        'library_glfw.js',
+        'library_uuid.js',
+        'library_glew.js',
+        'library_signals.js',
+        'library_idbstore.js',
+        'library_async.js',
+        'library_vr.js'
       ]);
     }
-    libraries = libraries.concat([
-      'library_sdl.js',
-      'library_gl.js',
-      'library_glut.js',
-      'library_xlib.js',
-      'library_egl.js',
-      'library_openal.js',
-      'library_glfw.js',
-      'library_uuid.js',
-      'library_glew.js',
-      'library_html5.js',
-      'library_signals.js',
-      'library_idbstore.js',
-      'library_async.js',
-      'library_vr.js'
-    ]).concat(additionalLibraries);
+
+    // If there are any explicitly specified system JS libraries to link to, add those to link.
+    if (SYSTEM_JS_LIBRARIES) {
+      SYSTEM_JS_LIBRARIES = SYSTEM_JS_LIBRARIES.split(',');
+      libraries = libraries.concat(SYSTEM_JS_LIBRARIES);
+    }
+
+    libraries = libraries.concat(additionalLibraries);
 
     if (BOOTSTRAPPING_STRUCT_INFO) libraries = ['library_bootstrap_structInfo.js', 'library_formatString.js'];
     if (ONLY_MY_CODE) {

src/settings.js

@@ -513,6 +513,9 @@ var ERROR_ON_MISSING_LIBRARIES = 0; // If set to 1, any -lfoo directives pointin
                                     // building with -s ERROR_ON_MISSING_LIBRARIES=0 setting,
                                     // prefer to set that option explicitly in your build system.
 
+var SYSTEM_JS_LIBRARIES = []; // Specifies a list of Emscripten-provided JS libraries to link against.
+                              // (internal, use -lfoo or -lfoo.js to link to Emscripten system JS libraries)
+
 var SMALL_XHR_CHUNKS = 0; // Use small chunk size for binary synchronous XHR's in Web Workers.
                           // Used for testing.
                           // See test_chunked_synchronous_xhr in runner.py and library.js.