Add nodefs readdir handling for directories that contain exotic entries (emscripten-core#22925)

Resolves emscripten-core#22924.

Author: hoodmane

src/library_syscall.js

@@ -695,9 +695,9 @@ var SyscallsLibrary = {
     var pos = 0;
     var off = FS.llseek(stream, 0, {{{ cDefs.SEEK_CUR }}});
 
-    var idx = Math.floor(off / struct_size);
-
-    while (idx < stream.getdents.length && pos + struct_size <= count) {
+    var startIdx = Math.floor(off / struct_size);
+    var endIdx = Math.min(stream.getdents.length, startIdx + Math.floor(count/struct_size))
+    for (var idx = startIdx; idx < endIdx; idx++) {
       var id;
       var type;
       var name = stream.getdents[idx];
@@ -711,7 +711,17 @@ var SyscallsLibrary = {
         type = 4; // DT_DIR
       }
       else {
-        var child = FS.lookupNode(stream.node, name);
+        var child;
+        try {
+          child = FS.lookupNode(stream.node, name);
+        } catch (e) {
+          // If the entry is not a directory, file, or symlink, nodefs
+          // lookupNode will raise EINVAL. Skip these and continue.
+          if (e?.errno === {{{ cDefs.EINVAL }}}) {
+            continue;
+          }
+          throw e;
+        }
         id = child.id;
         type = FS.isChrdev(child.mode) ? 2 :  // DT_CHR, character device.
                FS.isDir(child.mode) ? 4 :     // DT_DIR, directory.
@@ -727,7 +737,6 @@ var SyscallsLibrary = {
       {{{ makeSetValue('dirp + pos', C_STRUCTS.dirent.d_type, 'type', 'i8') }}};
       stringToUTF8(name, dirp + pos + {{{ C_STRUCTS.dirent.d_name }}}, 256);
       pos += struct_size;
-      idx += 1;
     }
     FS.llseek(stream, idx * struct_size, {{{ cDefs.SEEK_SET }}});
     return pos;

test/fs/test_nodefs_readdir.out

@@ -0,0 +1,13 @@
+listing contents of dir=/
+.
+..
+tmp
+home
+dev
+proc
+listing contents of dir=/working
+existing
+stdout
+test_nodefs_readdir.js
+test_nodefs_readdir.wasm
+success

test/fs/test_nodefs_readdir.wasm2js.out

@@ -0,0 +1,12 @@
+listing contents of dir=/
+.
+..
+tmp
+home
+dev
+proc
+listing contents of dir=/working
+existing
+stdout
+test_nodefs_readdir.js
+success

test/fs/test_nodefs_readdir.wasmfs.out

@@ -0,0 +1,14 @@
+listing contents of dir=/
+.
+..
+dev
+tmp
+listing contents of dir=/working
+.
+..
+existing
+named_pipe
+stdout
+test_nodefs_readdir.js
+test_nodefs_readdir.wasm
+success

test/test_core.py

@@ -5799,14 +5799,24 @@ def test_fs_nodefs_nofollow(self):
     self.emcc_args += ['-lnodefs.js']
     self.do_runf('fs/test_nodefs_nofollow.c', 'success')
 
+  @crossplatform
   @requires_node
   def test_fs_nodefs_readdir(self):
     # externally setup an existing folder structure: existing/a
     if self.get_setting('WASMFS'):
       self.set_setting('FORCE_FILESYSTEM')
+    if not WINDOWS:
+      # Add an entry that isn't a directory, file, or link to test that we handle
+      # it correctly.
+      os.mkfifo('named_pipe')
     os.makedirs('existing/a')
     self.emcc_args += ['-lnodefs.js']
-    self.do_runf('fs/test_nodefs_readdir.c', 'success')
+    suffix = ''
+    if self.get_setting('WASMFS'):
+      suffix = '.wasmfs'
+    elif self.is_wasm2js():
+      suffix = ".wasm2js"
+    self.do_run_in_out_file_test('fs/test_nodefs_readdir.c', out_suffix=suffix)
 
   @requires_node
   @crossplatform