[WasmFS] Skip root directory setup under NODERAWFS

system/lib/wasmfs/backend.h

@@ -21,6 +21,8 @@ class Backend {
   virtual std::shared_ptr<Directory> createDirectory(mode_t mode) = 0;
   virtual std::shared_ptr<Symlink> createSymlink(std::string target) = 0;
 
+  virtual bool shouldPopulateRoot() { return true; }
+
   virtual ~Backend() = default;
 };
 

system/lib/wasmfs/backends/node_backend.cpp

@@ -296,6 +296,8 @@ class NodeBackend : public Backend {
   std::shared_ptr<Symlink> createSymlink(std::string target) override {
     WASMFS_UNREACHABLE("TODO: implement NodeBackend::createSymlink");
   }
+
+  virtual bool shouldPopulateRoot() override { return false; }
 };
 
 // TODO: symlink

system/lib/wasmfs/wasmfs.cpp

@@ -106,8 +106,14 @@ std::shared_ptr<Directory> WasmFS::initRootDirectory() {
   // The root directory is its own parent.
   lockedRoot.setParent(rootDirectory);
 
+  // Skip setting up the root directory when not needed (e.g. in NODERAWFS
+  // mode).
+  if (!rootBackend->shouldPopulateRoot()) {
+    return rootDirectory;
+  }
+
   // If the /dev/ directory does not already exist, create it. (It may already
-  // exist in NODERAWFS mode, or if those files have been preloaded.)
+  // exist if those files have been preloaded.)
   auto devDir = lockedRoot.insertDirectory("dev", S_IRUGO | S_IXUGO);
   if (devDir) {
     auto lockedDev = devDir->locked();

test/codesize/test_codesize_cxx_wasmfs.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 7056,
   "a.out.js.gz": 3322,
-  "a.out.nodebug.wasm": 172695,
-  "a.out.nodebug.wasm.gz": 63383,
-  "total": 179751,
-  "total_gz": 66705,
+  "a.out.nodebug.wasm": 172722,
+  "a.out.nodebug.wasm.gz": 63393,
+  "total": 179778,
+  "total_gz": 66715,
   "sent": [
     "__cxa_throw",
     "_abort_js",

test/codesize/test_codesize_files_wasmfs.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 5487,
   "a.out.js.gz": 2586,
-  "a.out.nodebug.wasm": 58324,
-  "a.out.nodebug.wasm.gz": 18215,
-  "total": 63811,
-  "total_gz": 20801,
+  "a.out.nodebug.wasm": 58349,
+  "a.out.nodebug.wasm.gz": 18247,
+  "total": 63836,
+  "total_gz": 20833,
   "sent": [
     "a (emscripten_date_now)",
     "b (emscripten_err)",

test/test_other.py

@@ -5554,6 +5554,8 @@ def test_fsync(self, args):
   def test_fs_dev_random(self):
     if WINDOWS and self.get_setting('NODERAWFS'):
       self.skipTest('Crashes on Windows and NodeFS')
+    if self.get_setting('NODERAWFS') and self.get_setting('WASMFS'):
+      self.skipTest('https://github.com/emscripten-core/emscripten/issues/24830')
     self.do_runf('fs/test_fs_dev_random.c', 'done\n')
 
   @parameterized({
@@ -13274,6 +13276,8 @@ def test_unistd_chown(self):
 
   @wasmfs_all_backends
   def test_wasmfs_getdents(self):
+    if self.get_setting('NODERAWFS'):
+      self.skipTest('test expectations assumes /dev is virtualized')
     # Run only in WASMFS for now.
     self.set_setting('FORCE_FILESYSTEM')
     self.do_run_in_out_file_test('wasmfs/wasmfs_getdents.c')