Convert Imports to Indirect Calls for Dynamic Linking

emscripten.py

@@ -2206,8 +2206,25 @@ def emscript_wasm_backend(infile, outfile, memfile, compiler_engine,
   #   * Run wasm-emscripten-finalize to extract metadata and modify the binary
   #     to use emscripten's wasm<->JS ABI
   #   * Use the metadata to generate the JS glue that goes with the wasm
+  if shared.Settings.MAIN_MODULE:
+    # Run compile_settings here to retrieve all the JS library functions.
+    # Unfortunately, we need to run it later again to capture the exported functions
+    # from the Wasm
+    glue, forwarded_data = compile_settings(compiler_engine, temp_files)
+    forwarded_json = json.loads(forwarded_data)
+    library_fns = forwarded_json['Functions']['libraryFunctions']
+    library_fns_list = []
+    for name in library_fns:
+      library_fns_list.append(name)
+
+    js_symbols = infile + '.js_symbols'
+    with open(js_symbols, 'w') as js_symbols_file:
+      for sym in library_fns_list:
+        js_symbols_file.write(sym + '\n')
+  else:
+    js_symbols = []
 
-  metadata = finalize_wasm(temp_files, infile, outfile, memfile, DEBUG)
+  metadata = finalize_wasm(temp_files, infile, outfile, memfile, DEBUG, js_symbols)
 
   update_settings_glue(metadata, DEBUG)
 
@@ -2318,7 +2335,7 @@ def remove_trailing_zeros(memfile):
     f.write(mem_data[:end])
 
 
-def finalize_wasm(temp_files, infile, outfile, memfile, DEBUG):
+def finalize_wasm(temp_files, infile, outfile, memfile, DEBUG, libraryfile):
   basename = shared.unsuffixed(outfile.name)
   wasm = basename + '.wasm'
   base_wasm = infile
@@ -2365,6 +2382,9 @@ def finalize_wasm(temp_files, infile, outfile, memfile, DEBUG):
     args.append('--pass-arg=legalize-js-interface-export-originals')
   if shared.Settings.FULL_DWARF:
     args.append('--dwarf')
+
+  if shared.Settings.MAIN_MODULE and libraryfile:
+    args.append('--pass-arg=js-symbols@%s' % libraryfile)
   stdout = shared.Building.run_binaryen_command('wasm-emscripten-finalize',
                                                 infile=base_wasm,
                                                 outfile=wasm,

tests/test_core.py

@@ -8559,6 +8559,41 @@ def test_safe_stack_dylink(self):
       }
     ''', ['abort(stack overflow)', '__handle_stack_overflow'], assert_returncode=None)
 
+  @no_fastcomp('WASM backend convert imports to indirect calls')
+  @needs_dlfcn
+  def test_dylink_imports_to_indirect_calls(self):
+    # The ImportsToIndirectCalls pass in Binaryen should not allocate a new fp$ for
+    # imports that are already address taken. Test out both cases whereby the imports
+    # are either used directly or thru its address.
+    self.set_setting('EXIT_RUNTIME', 1)
+    self.dylink_test(main=r'''
+      #include <stdio.h>
+      extern int sidey();
+      extern int sidey2();
+      typedef int (*func)();
+      int mainy() {
+        return 19;
+      }
+
+      int main(int argc, char **argv) {
+        sidey();
+        func funcPtr = (0 == argc) ? sidey:sidey2;
+        funcPtr();
+        return 0;
+      }
+    ''', side=r'''
+      #include <stdio.h>
+      int sidey() {
+        printf("sidey says %d ", 17);
+        return 17;
+      }
+
+      int sidey2() {
+        printf("sidey2 says %d", 18);
+        return 18;
+      }
+    ''', expected='sidey says 17 sidey2 says 18', need_reverse=False)
+
   @also_with_standalone_wasm
   def test_undefined_main(self):
     # By default in emscripten we allow main to be undefined.  Its used when