Enable EXPORT_ALL in main modules with the wasm backend

emcc.py

@@ -1151,11 +1151,20 @@ def check(input_file):
 
     if shared.Settings.MAIN_MODULE:
       assert not shared.Settings.SIDE_MODULE
-      if shared.Settings.MAIN_MODULE != 2:
+      if shared.Settings.MAIN_MODULE == 1:
+        # Main modules must provide all JS library functions to side modules, as they
+        # may require them (in main module mode 2, the user must specify which
+        # using the normal exporting method).
         shared.Settings.INCLUDE_FULL_LIBRARY = 1
+        shared.Settings.EXPORT_ALL = 1
     elif shared.Settings.SIDE_MODULE:
       assert not shared.Settings.MAIN_MODULE
-      options.memory_init_file = False # memory init file is not supported with asm.js side modules, must be executable synchronously (for dlopen)
+      # memory init file is not supported with asm.js side modules, must be executable synchronously (for dlopen)
+      options.memory_init_file = False
+      # fastcomp dynamic linking is a little odd in that EXPORT_ALL matters
+      # even for side modules.
+      if not shared.Settings.WASM_BACKEND and shared.Settings.SIDE_MODULE == 1:
+        shared.Settings.EXPORT_ALL = 1
 
     if shared.Settings.MAIN_MODULE or shared.Settings.SIDE_MODULE:
       assert shared.Settings.ASM_JS, 'module linking requires asm.js output (-s ASM_JS=1)'

src/settings.js

@@ -785,9 +785,12 @@ var NODE_CODE_CACHING = 0;
 // there, you are in effect removing it).
 var EXPORTED_FUNCTIONS = ['_main'];
 
-// If true, we export all the symbols. Note that this does *not* affect LLVM, so
-// it can still eliminate functions as dead. This just exports them on the
-// Module object.
+// If true, we export all the symbols that are present in JS onto the Module
+// object. This does not affect which symbols will be present - it does not
+// prevent DCE or cause anything to be included in linking. It only does
+//   Module['X'] = X;
+// for all X that end up in the JS file. This is useful to export the JS
+// library functions on Module, for things like dynamic linking.
 var EXPORT_ALL = 0;
 
 // Export all bindings generator functions (prefixed with emscripten_bind_). This

src/support.js

@@ -508,6 +508,11 @@ function loadWebAssemblyModule(binary, flags) {
           return obj[prop] = function() {
             if (!fp) {
               var f = resolveSymbol(name, 'function', legalized);
+#if ASSERTIONS
+              // this resolved symbol must exist, as we are about to try to
+              // add it to the table; error clearly here instead of there.
+              assert(f, 'could not resolve: ' + name);
+#endif
               fp = addFunction(f, sig);
             }
             return fp;

tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE_2.exports

@@ -1,9 +1,9 @@
-___errno_location
-__apply_relocations
-_main
-_malloc
-dynCall_X
-dynCall_ii
-dynCall_iiii
-dynCall_iiiii
-stackAlloc
+___errno_location
+__apply_relocations
+_main
+_malloc
+dynCall_X
+dynCall_ii
+dynCall_iiii
+dynCall_iiiii
+stackAlloc

tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE_2.imports

@@ -1,13 +1,13 @@
-STACKTOP
-___wasi_fd_write
-__memory_base
-__table_base
-_emscripten_get_heap_size
-_emscripten_memcpy_big
-_emscripten_resize_heap
-abort
-fb
-gb
-memory
-setTempRet0
-table
+STACKTOP
+___wasi_fd_write
+__memory_base
+__table_base
+_emscripten_get_heap_size
+_emscripten_memcpy_big
+_emscripten_resize_heap
+abort
+fb
+gb
+memory
+setTempRet0
+table

tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE_2.sent

@@ -1,13 +1,13 @@
-STACKTOP
-___wasi_fd_write
-__memory_base
-__table_base
-_emscripten_get_heap_size
-_emscripten_memcpy_big
-_emscripten_resize_heap
-abort
-fb
-gb
-memory
-setTempRet0
-table
+STACKTOP
+___wasi_fd_write
+__memory_base
+__table_base
+_emscripten_get_heap_size
+_emscripten_memcpy_big
+_emscripten_resize_heap
+abort
+fb
+gb
+memory
+setTempRet0
+table

tests/test_core.py

@@ -2555,12 +2555,10 @@ def test_nestedstructs(self):
   def prep_dlfcn_lib(self):
     self.clear_setting('MAIN_MODULE')
     self.set_setting('SIDE_MODULE')
-    self.set_setting('EXPORT_ALL')
 
   def prep_dlfcn_main(self):
     self.set_setting('MAIN_MODULE')
     self.clear_setting('SIDE_MODULE')
-    self.set_setting('EXPORT_ALL')
 
     create_test_file('lib_so_pre.js', '''
     if (!Module['preRun']) Module['preRun'] = [];
@@ -3566,9 +3564,6 @@ def test_dlfcn_feature_in_lib(self, js_engines):
     self.do_run(src, 'float: 42.\n', js_engines=js_engines)
 
   def dylink_test(self, main, side, expected=None, header=None, main_emcc_args=[], force_c=False, need_reverse=True, auto_load=True, **kwargs):
-    # shared settings
-    self.set_setting('EXPORT_ALL', 1)
-
     if header:
       create_test_file('header.h', header)
 

tests/test_other.py

@@ -6667,7 +6667,7 @@ def test_main_module_without_exceptions_message(self):
     def build_main(args):
       print(args)
       with env_modify({'EMCC_FORCE_STDLIBS': 'libc++abi'}):
-        run_process([PYTHON, EMCC, 'main.cpp', '-s', 'MAIN_MODULE=1', '-s', 'EXPORT_ALL',
+        run_process([PYTHON, EMCC, 'main.cpp', '-s', 'MAIN_MODULE=1',
                      '--embed-file', 'libside.wasm'] + args)
 
     build_main([])
@@ -8220,7 +8220,7 @@ def test_metadce_cxx_fastcomp(self, *args):
     # don't compare the # of functions in a main module, which changes a lot
     # TODO(sbc): Investivate why the number of exports is order of magnitude
     # larger for wasm backend.
-    'main_module_2': (['-O3', '-s', 'MAIN_MODULE=2'],   12, [], [],  10770,   12,   10, None), # noqa
+    'main_module_2': (['-O3', '-s', 'MAIN_MODULE=2'],   12, [], [],  10652,   12,   10, None), # noqa
   })
   @no_fastcomp()
   def test_metadce_hello(self, *args):