Fix fd_sync under pthreads

This function is marked as `__async: 'auto'` which means it should
return a promise when run in proxied mode on the main thread.  However
it wasn't always returning a promise.   Adding the `async` keyword
is the simplest way to ensure it always returns a promise.

Also, update the `wrapSyscallFunction` function to preserve the async
keyword.

Replaces: #26209

Author: sbc100

src/lib/libcore.js

@@ -2605,7 +2605,7 @@ function wrapSyscallFunction(x, library, isWasi) {
   post = handler + post;
 
   if (pre || post) {
-    t = modifyJSFunction(t, (args, body) => `function (${args}) {\n${pre}${body}${post}}\n`);
+    t = modifyJSFunction(t, (args, body, async_) => `${async_}function (${args}) {\n${pre}${body}${post}}\n`);
   }
 
   library[x] = eval('(' + t + ')');

src/lib/libwasi.js

@@ -540,27 +540,32 @@ var WasiLibrary = {
     return 0;
   },
 
+#if SYSCALLS_REQUIRE_FILESYSTEM
   fd_sync__async: 'auto',
   fd_sync: (fd) => {
-#if SYSCALLS_REQUIRE_FILESYSTEM
     var stream = SYSCALLS.getStreamFromFD(fd);
     var rtn = stream.stream_ops?.fsync?.(stream);
-#if ASYNCIFY
-    var mount = stream.node.mount;
-    if (mount.type.syncfs) {
-      return new Promise((resolve) => {
+#if ASYNCIFY || PTHREADS
+    return new Promise((resolve) => {
+      var mount = stream.node.mount;
+      if (mount && mount.type.syncfs) {
         mount.type.syncfs(mount, false, (err) => resolve(err ? {{{ cDefs.EIO }}} : 0));
-      });
-    }
-#endif // ASYNCIFY
+      } else {
+        resolve(rtn);
+      }
+    });
+#else
     return rtn;
+#endif // ASYNCIFY || PTHREADS
+  },
 #else // SYSCALLS_REQUIRE_FILESYSTEM
+  fd_sync: (fd) => {
 #if ASSERTIONS
     abort('fd_sync called without SYSCALLS_REQUIRE_FILESYSTEM');
 #endif
     return {{{ cDefs.ENOSYS }}};
-#endif // SYSCALLS_REQUIRE_FILESYSTEM
   },
+#endif // SYSCALLS_REQUIRE_FILESYSTEM
 
   // random.h
 

test/fs/test_memfs_fsync.c

@@ -23,10 +23,10 @@ int main() {
   struct stat st;
 
   // a file whose contents are just 'az'
-  rtn = stat("/wakaka.txt", &st);
+  rtn = stat("wakaka.txt", &st);
   assert(rtn == -1 && errno == ENOENT);
 
-  fd = open("/wakaka.txt", O_RDWR | O_CREAT, 0666);
+  fd = open("wakaka.txt", O_RDWR | O_CREAT, 0666);
   assert(fd >= 0);
 
   rtn = write(fd, "az", 2);
@@ -38,5 +38,6 @@ int main() {
   rtn = close(fd);
   assert(rtn == 0);
 
+  printf("success\n");
   return 0;
 }

test/test_browser.py

@@ -1325,9 +1325,7 @@ def test_fs_idbfs_fsync(self):
     self.btest('fs/test_idbfs_fsync.c', '1', cflags=args + [f'-DSECRET="{secret}"', '-lidbfs.js'])
 
   def test_fs_memfs_fsync(self):
-    args = ['-sASYNCIFY', '-sEXIT_RUNTIME']
-    secret = str(time.time())
-    self.btest_exit('fs/test_memfs_fsync.c', cflags=args + [f'-DSECRET="{secret}"'])
+    self.btest_exit('fs/test_memfs_fsync.c', cflags=['-sASYNCIFY', '-sEXIT_RUNTIME'])
 
   def test_fs_workerfs(self):
     create_file('pre.js', '''

test/test_other.py

@@ -58,6 +58,7 @@
   also_with_asan,
   also_with_minimal_runtime,
   also_with_modularize,
+  also_with_nodefs_both,
   also_with_noderawfs,
   also_with_standalone_wasm,
   also_with_wasm2js,
@@ -5525,7 +5526,16 @@ def test_dashM_respect_dashO(self):
   @with_all_fs
   @crossplatform
   def test_fs_bad_lookup(self):
-    self.do_runf(path_from_root('test/fs/test_fs_bad_lookup.c'), expected_output='ok')
+    self.do_runf('fs/test_fs_bad_lookup.c', 'ok')
+
+  @also_with_nodefs_both
+  @crossplatform
+  @parameterized({
+    '': ([],),
+    'pthreads': (['-pthread', '-sPROXY_TO_PTHREAD', '-sEXIT_RUNTIME'],),
+  })
+  def test_fsync(self, args):
+    self.do_runf('fs/test_memfs_fsync.c', 'success', cflags=args)
 
   @with_all_fs
   @crossplatform