Make RTLD_LOCAL work correctly for preloaded DSOs (emscripten-core#21985)

Follow-up to commit c9a5e63, for the FS.createPreloadedFile()
case.

Make sure loadWebAssemblyModule() and loadDynamicLibrary()
are called with a valid 'localScope' object when invoked
from the .so file type preload handler.

Author: msorvig

src/library_dylink.js

@@ -26,7 +26,7 @@ var LibraryDylink = {
         // than just running the promises in parallel, this makes a chain of
         // promises to run in series.
         wasmPlugin['promiseChainEnd'] = wasmPlugin['promiseChainEnd'].then(
-          () => loadWebAssemblyModule(byteArray, {loadAsync: true, nodelete: true}, name)).then(
+          () => loadWebAssemblyModule(byteArray, {loadAsync: true, nodelete: true}, name, {})).then(
             (exports) => {
 #if DYLINK_DEBUG
               dbg(`registering preloadedWasm: ${name}`);
@@ -877,7 +877,7 @@ var LibraryDylink = {
     if (flags.loadAsync) {
       return metadata.neededDynlibs
         .reduce((chain, dynNeeded) => chain.then(() =>
-          loadDynamicLibrary(dynNeeded, flags)
+          loadDynamicLibrary(dynNeeded, flags, localScope)
         ), Promise.resolve())
         .then(loadModule);
     }

test/test_core.py

@@ -3958,6 +3958,52 @@ def test_dlfcn_rtld_local(self):
 
     self.do_runf('main.c', 'main\nfunc_a\nfunc_sub\nfunc_b\nfunc_sub\ndone\n')
 
+  @needs_dylink
+  def test_dlfcn_preload(self):
+    # Create chain of dependencies and load the first libary with preload plugin.
+    # main -> libb.so -> liba.so
+    create_file('liba.c', r'''
+      #include <stdio.h>
+      int liba_fun() {
+        return 23;
+      }
+    ''')
+    self.build_dlfcn_lib('liba.c', outfile='liba.so')
+
+    create_file('libb.c', r'''
+      #include <stdio.h>
+      int liba_fun();
+
+      int libb_fun() {
+        return liba_fun()*2;
+      }
+    ''')
+    self.build_dlfcn_lib('libb.c', outfile='libb.so', emcc_args=['liba.so'])
+
+    self.prep_dlfcn_main(['--preload-file', 'libb.so', '--use-preload-plugins'])
+    create_file('main.c', r'''
+      #include <assert.h>
+      #include <dlfcn.h>
+      #include <stdio.h>
+      #include <sys/stat.h>
+
+      int main() {
+        // Check the file exists in the VFS
+        struct stat statbuf;
+        assert(stat("/libb.so", &statbuf) == 0);
+        void *lib_handle = dlopen("/libb.so", RTLD_LOCAL | RTLD_NOW);
+        assert(lib_handle);
+        typedef int (*intfunc)();
+        intfunc x = (intfunc)dlsym(lib_handle, "libb_fun");
+        assert(x);
+        assert(x() == 46);
+        printf("done\n");
+        return 0;
+
+      }
+    ''')
+    self.do_runf('main.c', 'done\n')
+
   def dylink_test(self, main, side, expected=None, header=None, force_c=False,
                   main_module=2, **kwargs):
     # Same as dylink_testf but take source code in string form