diff --git a/src/lib/libfs.js b/src/lib/libfs.js
index 4907180698353..8f7a58df004fd 100644
--- a/src/lib/libfs.js
+++ b/src/lib/libfs.js
@@ -54,7 +54,7 @@ FS.staticInit();`;
     devices: {},
     streams: [],
     nextInode: 1,
-    nameTable: null,
+    nameTable: [],
     currentPath: '/',
     initialized: false,
     // Whether we are currently ignoring permissions. Useful when preparing the
@@ -373,7 +373,7 @@ FS.staticInit();`;
       // if we failed to find it in the cache, call into the VFS
       return FS.lookup(parent, name);
     },
-    createNode(parent, name, mode, rdev) {
+    createNode(parent, name, mode, rdev = undefined) {
 #if ASSERTIONS
       assert(typeof parent == 'object')
 #endif
@@ -815,7 +815,7 @@ FS.staticInit();`;
       return FS.mknod(path, mode, 0);
     },
     // Creates a whole directory tree chain if it doesn't yet exist
-    mkdirTree(path, mode) {
+    mkdirTree(path, mode = 0o777) {
       var dirs = path.split('/');
       var d = '';
       for (var dir of dirs) {
@@ -829,7 +829,7 @@ FS.staticInit();`;
         }
       }
     },
-    mkdev(path, mode, dev) {
+    mkdev(path, mode, dev = undefined) {
       if (typeof dev == 'undefined') {
         dev = mode;
         mode = 0o666;
@@ -1040,7 +1040,7 @@ FS.staticInit();`;
       }
       return link.node_ops.readlink(link);
     },
-    stat(path, dontFollow) {
+    stat(path, dontFollow = false) {
       var lookup = FS.lookupPath(path, { follow: !dontFollow });
       var node = lookup.node;
       var getattr = FS.checkOpExists(node.node_ops.getattr, {{{ cDefs.EPERM }}});
@@ -1058,14 +1058,14 @@ FS.staticInit();`;
     lstat(path) {
       return FS.stat(path, true);
     },
-    doChmod(stream, node, mode, dontFollow) {
+    doChmod(stream, node, mode, dontFollow = false) {
       FS.doSetAttr(stream, node, {
         mode: (mode & {{{ cDefs.S_IALLUGO }}}) | (node.mode & ~{{{ cDefs.S_IALLUGO }}}),
         ctime: Date.now(),
         dontFollow
       });
     },
-    chmod(path, mode, dontFollow) {
+    chmod(path, mode, dontFollow = false) {
       var node;
       if (typeof path == 'string') {
         var lookup = FS.lookupPath(path, { follow: !dontFollow });
@@ -1082,14 +1082,14 @@ FS.staticInit();`;
       var stream = FS.getStreamChecked(fd);
       FS.doChmod(stream, stream.node, mode, false);
     },
-    doChown(stream, node, dontFollow) {
+    doChown(stream, node, dontFollow = false) {
       FS.doSetAttr(stream, node, {
         timestamp: Date.now(),
         dontFollow
         // we ignore the uid / gid for now
       });
     },
-    chown(path, uid, gid, dontFollow) {
+    chown(path, uid, gid, dontFollow = false) {
       var node;
       if (typeof path == 'string') {
         var lookup = FS.lookupPath(path, { follow: !dontFollow });
@@ -1142,7 +1142,7 @@ FS.staticInit();`;
       }
       FS.doTruncate(stream, stream.node, len);
     },
-    utime(path, atime, mtime, dontFollow) {
+    utime(path, atime, mtime, dontFollow = false) {
       var lookup = FS.lookupPath(path, { follow: !dontFollow });
       FS.doSetAttr(null, lookup.node, {
         atime: atime,
@@ -1305,7 +1305,7 @@ FS.staticInit();`;
 #endif
       return stream.position;
     },
-    read(stream, buffer, offset, length, position) {
+    read(stream, buffer, offset, length, position = undefined) {
 #if ASSERTIONS
       assert(offset >= 0);
 #endif
@@ -1342,7 +1342,7 @@ FS.staticInit();`;
     /**
      * @param {TypedArray} buffer
      */
-    write(stream, buffer, offset, length, position, canOwn) {
+    write(stream, buffer, offset, length, position = undefined, canOwn = undefined) {
 #if ASSERTIONS
       assert(offset >= 0);
       assert(buffer.subarray, 'FS.write expects a TypedArray');
@@ -1575,7 +1575,7 @@ FS.staticInit();`;
 #endif
     },
     staticInit() {
-      FS.nameTable = new Array(4096);
+      FS.nameTable.length = 4096;
 
       FS.mount(MEMFS, {}, '/');
 
@@ -1599,7 +1599,7 @@ FS.staticInit();`;
 #endif
       };
     },
-    init(input, output, error) {
+    init(input = undefined, output = undefined, error = undefined) {
 #if ASSERTIONS
       assert(!FS.initialized, 'FS.init was previously called. If you want to initialize later with custom parameters, remove any earlier calls (note that one is automatically added to the generated code)');
 #endif
@@ -1635,14 +1635,14 @@ FS.staticInit();`;
     //
     // old v1 compatibility functions
     //
-    findObject(path, dontResolveLastLink) {
+    findObject(path, dontResolveLastLink = false) {
       var ret = FS.analyzePath(path, dontResolveLastLink);
       if (!ret.exists) {
         return null;
       }
       return ret.object;
     },
-    analyzePath(path, dontResolveLastLink) {
+    analyzePath(path, dontResolveLastLink = false) {
       // operate from within the context of the symlink's target
       try {
         var lookup = FS.lookupPath(path, { follow: !dontResolveLastLink });
@@ -1670,7 +1670,7 @@ FS.staticInit();`;
       };
       return ret;
     },
-    createPath(parent, path, canRead, canWrite) {
+    createPath(parent, path, canRead = undefined, canWrite = undefined) {
       parent = typeof parent == 'string' ? parent : FS.getPath(parent);
       var parts = path.split('/').reverse();
       while (parts.length) {
@@ -1686,7 +1686,7 @@ FS.staticInit();`;
       }
       return current;
     },
-    createFile(parent, name, properties, canRead, canWrite) {
+    createFile(parent, name, properties, canRead = undefined, canWrite = undefined) {
       var path = PATH.join2(typeof parent == 'string' ? parent : FS.getPath(parent), name);
       var mode = FS_getMode(canRead, canWrite);
       return FS.create(path, mode);
@@ -1694,7 +1694,7 @@ FS.staticInit();`;
     /**
      * @param {TypedArray|Array|string=} data
      */
-    createDataFile(parent, name, data, canRead, canWrite, canOwn) {
+    createDataFile(parent, name, data = undefined, canRead = undefined, canWrite = undefined, canOwn = undefined) {
       var path = name;
       if (parent) {
         parent = typeof parent == 'string' ? parent : FS.getPath(parent);
@@ -1712,7 +1712,7 @@ FS.staticInit();`;
         FS.chmod(node, mode);
       }
     },
-    createDevice(parent, name, input, output) {
+    createDevice(parent, name, input = undefined, output = undefined) {
       var path = PATH.join2(typeof parent == 'string' ? parent : FS.getPath(parent), name);
       var mode = FS_getMode(!!input, !!output);
       FS.createDevice.major ??= 64;
@@ -1789,7 +1789,7 @@ FS.staticInit();`;
     // Creates a file record for lazy-loading from a URL. XXX This requires a synchronous
     // XHR, which is not possible in browsers except in a web worker! Use preloading,
     // either --preload-file in emcc or FS.createPreloadedFile
-    createLazyFile(parent, name, url, canRead, canWrite) {
+    createLazyFile(parent, name, url, canRead = undefined, canWrite = undefined) {
       // Lazy chunked Uint8Array (implements get and length from Uint8Array).
       // Actual getting is abstracted away for eventual reuse.
       class LazyUint8Array {
diff --git a/src/lib/libmemfs.js b/src/lib/libmemfs.js
index 5c0b4d4f53eda..76f79f47b8915 100644
--- a/src/lib/libmemfs.js
+++ b/src/lib/libmemfs.js
@@ -11,7 +11,7 @@ addToLibrary({
     mount(mount) {
       return MEMFS.createNode(null, '/', {{{ cDefs.S_IFDIR | 0o777 }}}, 0);
     },
-    createNode(parent, name, mode, dev) {
+    createNode(parent, name, mode, dev = undefined) {
       if (FS.isBlkdev(mode) || FS.isFIFO(mode)) {
         // not supported
         throw new FS.ErrnoError({{{ cDefs.EPERM }}});
@@ -186,7 +186,7 @@ addToLibrary({
         throw MEMFS.doesNotExistError;
 #endif
       },
-      mknod(parent, name, mode, dev) {
+      mknod(parent, name, mode, dev = undefined) {
         return MEMFS.createNode(parent, name, mode, dev);
       },
       rename(old_node, new_dir, new_name) {
diff --git a/src/lib/libnodefs.js b/src/lib/libnodefs.js
index dd839a36f93fd..c099765b0bf05 100644
--- a/src/lib/libnodefs.js
+++ b/src/lib/libnodefs.js
@@ -62,7 +62,7 @@ addToLibrary({
 #endif
       return NODEFS.createNode(null, '/', NODEFS.getMode(mount.opts.root), 0);
     },
-    createNode(parent, name, mode, dev) {
+    createNode(parent, name, mode, dev = undefined) {
       if (!FS.isDir(mode) && !FS.isFile(mode) && !FS.isLink(mode)) {
         throw new FS.ErrnoError({{{ cDefs.EINVAL }}});
       }
@@ -200,7 +200,7 @@ addToLibrary({
         var mode = NODEFS.getMode(path);
         return NODEFS.createNode(parent, name, mode);
       },
-      mknod(parent, name, mode, dev) {
+      mknod(parent, name, mode, dev = undefined) {
         var node = NODEFS.createNode(parent, name, mode, dev);
         // create the backing node for this in the fs root as well
         var path = NODEFS.realPath(node);
@@ -314,7 +314,7 @@ addToLibrary({
         return { ptr, allocated: true };
       },
       msync(stream, buffer, offset, length, mmapFlags) {
-        NODEFS.stream_ops.write(stream, buffer, 0, length, offset, false);
+        NODEFS.stream_ops.write(stream, buffer, 0, length, offset);
         // should we check if bytesWritten and length are the same?
         return 0;
       }
diff --git a/src/lib/libnoderawfs.js b/src/lib/libnoderawfs.js
index ce4afbdfa01da..ac4672e4c2e19 100644
--- a/src/lib/libnoderawfs.js
+++ b/src/lib/libnoderawfs.js
@@ -101,7 +101,7 @@ addToLibrary({
     readdir(...args) { return ['.', '..'].concat(fs.readdirSync(...args)); },
     unlink(...args) { fs.unlinkSync(...args); },
     readlink(...args) { return fs.readlinkSync(...args); },
-    stat(path, dontFollow) {
+    stat(path, dontFollow = false) {
       var stat = dontFollow ? fs.lstatSync(path) : fs.statSync(path);
       if (NODEFS.isWindows) {
         // Windows does not report the 'x' permission bit, so propagate read
@@ -133,7 +133,7 @@ addToLibrary({
     statfsStream(stream) {
       return FS.statfs(stream.path);
     },
-    chmod(path, mode, dontFollow) {
+    chmod(path, mode, dontFollow = false) {
       mode &= {{{ cDefs.S_IALLUGO }}};
       if (NODEFS.isWindows) {
         // Windows only supports S_IREAD / S_IWRITE (S_IRUSR / S_IWUSR)
@@ -171,7 +171,7 @@ addToLibrary({
       var stream = FS.getStreamChecked(fd);
       fs.ftruncateSync(stream.nfd, len);
     },
-    utime(path, atime, mtime, dontFollow) {
+    utime(path, atime, mtime, dontFollow = false) {
       // null here for atime or mtime means UTIME_OMIT was passed.  Since node
       // doesn't support this concept we need to first find the existing
       // timestamps in order to preserve them.
diff --git a/src/lib/libsockfs.js b/src/lib/libsockfs.js
index 44f9a934e5439..a2778f7acced9 100644
--- a/src/lib/libsockfs.js
+++ b/src/lib/libsockfs.js
@@ -209,7 +209,7 @@ addToLibrary({
       // these functions aren't actually sock_ops members, but we're
       // abusing the namespace to organize them
       //
-      createPeer(sock, addr, port) {
+      createPeer(sock, addr, port = undefined) {
         var ws;
 
         if (typeof addr == 'object') {
diff --git a/src/lib/libsyscall.js b/src/lib/libsyscall.js
index 38fa259ba4c87..cd95f5d24142a 100644
--- a/src/lib/libsyscall.js
+++ b/src/lib/libsyscall.js
@@ -17,7 +17,7 @@ var SyscallsLibrary = {
     // global constants
 
     // shared utilities
-    calculateAt(dirfd, path, allowEmpty) {
+    calculateAt(dirfd, path, allowEmpty = false) {
       if (PATH.isAbs(path)) {
         return path;
       }
@@ -947,7 +947,7 @@ var SyscallsLibrary = {
     path = SYSCALLS.getStr(path);
     path = SYSCALLS.calculateAt(dirfd, path);
     mode &= ~SYSCALLS.currentUmask;
-    FS.mkdir(path, mode, 0);
+    FS.mkdir(path, mode);
     return 0;
   },
   __syscall_mknodat: (dirfd, path, mode, dev) => {
diff --git a/test/codesize/test_codesize_cxx_ctors1.json b/test/codesize/test_codesize_cxx_ctors1.json
index ef85ddc7054d5..a0694a1959d2d 100644
--- a/test/codesize/test_codesize_cxx_ctors1.json
+++ b/test/codesize/test_codesize_cxx_ctors1.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 19224,
-  "a.out.js.gz": 8124,
+  "a.out.js": 19218,
+  "a.out.js.gz": 8121,
   "a.out.nodebug.wasm": 133971,
   "a.out.nodebug.wasm.gz": 51271,
-  "total": 153195,
-  "total_gz": 59395,
+  "total": 153189,
+  "total_gz": 59392,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_cxx_ctors2.json b/test/codesize/test_codesize_cxx_ctors2.json
index 9745a6316785d..71a1328e7d801 100644
--- a/test/codesize/test_codesize_cxx_ctors2.json
+++ b/test/codesize/test_codesize_cxx_ctors2.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 19201,
-  "a.out.js.gz": 8107,
+  "a.out.js": 19195,
+  "a.out.js.gz": 8105,
   "a.out.nodebug.wasm": 133403,
   "a.out.nodebug.wasm.gz": 50959,
-  "total": 152604,
-  "total_gz": 59066,
+  "total": 152598,
+  "total_gz": 59064,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_cxx_except.json b/test/codesize/test_codesize_cxx_except.json
index 8e083d22ec62b..37a674a597a8b 100644
--- a/test/codesize/test_codesize_cxx_except.json
+++ b/test/codesize/test_codesize_cxx_except.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 22917,
-  "a.out.js.gz": 9082,
+  "a.out.js": 22911,
+  "a.out.js.gz": 9079,
   "a.out.nodebug.wasm": 176383,
   "a.out.nodebug.wasm.gz": 58776,
-  "total": 199300,
-  "total_gz": 67858,
+  "total": 199294,
+  "total_gz": 67855,
   "sent": [
     "__cxa_begin_catch",
     "__cxa_end_catch",
diff --git a/test/codesize/test_codesize_cxx_except_wasm.json b/test/codesize/test_codesize_cxx_except_wasm.json
index acce5eb08a6f9..d1e55f9d362f7 100644
--- a/test/codesize/test_codesize_cxx_except_wasm.json
+++ b/test/codesize/test_codesize_cxx_except_wasm.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 19023,
-  "a.out.js.gz": 8039,
+  "a.out.js": 19017,
+  "a.out.js.gz": 8038,
   "a.out.nodebug.wasm": 149640,
   "a.out.nodebug.wasm.gz": 56311,
-  "total": 168663,
-  "total_gz": 64350,
+  "total": 168657,
+  "total_gz": 64349,
   "sent": [
     "_abort_js",
     "_tzset_js",
diff --git a/test/codesize/test_codesize_cxx_except_wasm_legacy.json b/test/codesize/test_codesize_cxx_except_wasm_legacy.json
index 7d2e3ac6023e4..a93b588230acd 100644
--- a/test/codesize/test_codesize_cxx_except_wasm_legacy.json
+++ b/test/codesize/test_codesize_cxx_except_wasm_legacy.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 19101,
-  "a.out.js.gz": 8065,
+  "a.out.js": 19095,
+  "a.out.js.gz": 8063,
   "a.out.nodebug.wasm": 147422,
   "a.out.nodebug.wasm.gz": 55982,
-  "total": 166523,
-  "total_gz": 64047,
+  "total": 166517,
+  "total_gz": 64045,
   "sent": [
     "_abort_js",
     "_tzset_js",
diff --git a/test/codesize/test_codesize_cxx_lto.json b/test/codesize/test_codesize_cxx_lto.json
index 5bf114b165af0..10cc5c1347880 100644
--- a/test/codesize/test_codesize_cxx_lto.json
+++ b/test/codesize/test_codesize_cxx_lto.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 18568,
-  "a.out.js.gz": 7818,
+  "a.out.js": 18562,
+  "a.out.js.gz": 7814,
   "a.out.nodebug.wasm": 101064,
   "a.out.nodebug.wasm.gz": 38292,
-  "total": 119632,
-  "total_gz": 46110,
+  "total": 119626,
+  "total_gz": 46106,
   "sent": [
     "a (emscripten_resize_heap)",
     "b (_setitimer_js)",
diff --git a/test/codesize/test_codesize_cxx_mangle.json b/test/codesize/test_codesize_cxx_mangle.json
index a9df7ddb5796f..0db79c3242a54 100644
--- a/test/codesize/test_codesize_cxx_mangle.json
+++ b/test/codesize/test_codesize_cxx_mangle.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 22967,
-  "a.out.js.gz": 9103,
+  "a.out.js": 22961,
+  "a.out.js.gz": 9100,
   "a.out.nodebug.wasm": 242663,
   "a.out.nodebug.wasm.gz": 81001,
-  "total": 265630,
-  "total_gz": 90104,
+  "total": 265624,
+  "total_gz": 90101,
   "sent": [
     "__cxa_begin_catch",
     "__cxa_end_catch",
diff --git a/test/codesize/test_codesize_cxx_noexcept.json b/test/codesize/test_codesize_cxx_noexcept.json
index 608a59b681293..a9206ee2b5d16 100644
--- a/test/codesize/test_codesize_cxx_noexcept.json
+++ b/test/codesize/test_codesize_cxx_noexcept.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 19224,
-  "a.out.js.gz": 8124,
+  "a.out.js": 19218,
+  "a.out.js.gz": 8121,
   "a.out.nodebug.wasm": 135882,
   "a.out.nodebug.wasm.gz": 51885,
-  "total": 155106,
-  "total_gz": 60009,
+  "total": 155100,
+  "total_gz": 60006,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_file_preload.expected.js b/test/codesize/test_codesize_file_preload.expected.js
index 6999515586248..c4f400b37a3b0 100644
--- a/test/codesize/test_codesize_file_preload.expected.js
+++ b/test/codesize/test_codesize_file_preload.expected.js
@@ -954,7 +954,7 @@ var MEMFS = {
   mount(mount) {
     return MEMFS.createNode(null, "/", 16895, 0);
   },
-  createNode(parent, name, mode, dev) {
+  createNode(parent, name, mode, dev = undefined) {
     if (FS.isBlkdev(mode) || FS.isFIFO(mode)) {
       // not supported
       throw new FS.ErrnoError(63);
@@ -1114,7 +1114,7 @@ var MEMFS = {
       }
       throw MEMFS.doesNotExistError;
     },
-    mknod(parent, name, mode, dev) {
+    mknod(parent, name, mode, dev = undefined) {
       return MEMFS.createNode(parent, name, mode, dev);
     },
     rename(old_node, new_dir, new_name) {
@@ -1361,7 +1361,7 @@ var FS = {
   devices: {},
   streams: [],
   nextInode: 1,
-  nameTable: null,
+  nameTable: [],
   currentPath: "/",
   initialized: false,
   ignorePermissions: true,
@@ -1623,7 +1623,7 @@ var FS = {
     // if we failed to find it in the cache, call into the VFS
     return FS.lookup(parent, name);
   },
-  createNode(parent, name, mode, rdev) {
+  createNode(parent, name, mode, rdev = undefined) {
     var node = new FS.FSNode(parent, name, mode, rdev);
     FS.hashAddNode(node);
     return node;
@@ -1994,7 +1994,7 @@ var FS = {
     mode |= 16384;
     return FS.mknod(path, mode, 0);
   },
-  mkdirTree(path, mode) {
+  mkdirTree(path, mode = 511) {
     var dirs = path.split("/");
     var d = "";
     for (var dir of dirs) {
@@ -2008,7 +2008,7 @@ var FS = {
       }
     }
   },
-  mkdev(path, mode, dev) {
+  mkdev(path, mode, dev = undefined) {
     if (typeof dev == "undefined") {
       dev = mode;
       mode = 438;
@@ -2206,7 +2206,7 @@ var FS = {
     }
     return link.node_ops.readlink(link);
   },
-  stat(path, dontFollow) {
+  stat(path, dontFollow = false) {
     var lookup = FS.lookupPath(path, {
       follow: !dontFollow
     });
@@ -2226,14 +2226,14 @@ var FS = {
   lstat(path) {
     return FS.stat(path, true);
   },
-  doChmod(stream, node, mode, dontFollow) {
+  doChmod(stream, node, mode, dontFollow = false) {
     FS.doSetAttr(stream, node, {
       mode: (mode & 4095) | (node.mode & ~4095),
       ctime: Date.now(),
       dontFollow
     });
   },
-  chmod(path, mode, dontFollow) {
+  chmod(path, mode, dontFollow = false) {
     var node;
     if (typeof path == "string") {
       var lookup = FS.lookupPath(path, {
@@ -2252,13 +2252,13 @@ var FS = {
     var stream = FS.getStreamChecked(fd);
     FS.doChmod(stream, stream.node, mode, false);
   },
-  doChown(stream, node, dontFollow) {
+  doChown(stream, node, dontFollow = false) {
     FS.doSetAttr(stream, node, {
       timestamp: Date.now(),
       dontFollow
     });
   },
-  chown(path, uid, gid, dontFollow) {
+  chown(path, uid, gid, dontFollow = false) {
     var node;
     if (typeof path == "string") {
       var lookup = FS.lookupPath(path, {
@@ -2315,7 +2315,7 @@ var FS = {
     }
     FS.doTruncate(stream, stream.node, len);
   },
-  utime(path, atime, mtime, dontFollow) {
+  utime(path, atime, mtime, dontFollow = false) {
     var lookup = FS.lookupPath(path, {
       follow: !dontFollow
     });
@@ -2457,7 +2457,7 @@ var FS = {
     stream.ungotten = [];
     return stream.position;
   },
-  read(stream, buffer, offset, length, position) {
+  read(stream, buffer, offset, length, position = undefined) {
     if (length < 0 || position < 0) {
       throw new FS.ErrnoError(28);
     }
@@ -2483,7 +2483,7 @@ var FS = {
     if (!seeking) stream.position += bytesRead;
     return bytesRead;
   },
-  write(stream, buffer, offset, length, position, canOwn) {
+  write(stream, buffer, offset, length, position = undefined, canOwn = undefined) {
     if (length < 0 || position < 0) {
       throw new FS.ErrnoError(28);
     }
@@ -2693,7 +2693,7 @@ var FS = {
     var stderr = FS.open("/dev/stderr", 1);
   },
   staticInit() {
-    FS.nameTable = new Array(4096);
+    FS.nameTable.length = 4096;
     FS.mount(MEMFS, {}, "/");
     FS.createDefaultDirectories();
     FS.createDefaultDevices();
@@ -2702,7 +2702,7 @@ var FS = {
       "MEMFS": MEMFS
     };
   },
-  init(input, output, error) {
+  init(input = undefined, output = undefined, error = undefined) {
     FS.initialized = true;
     // Allow Module.stdin etc. to provide defaults, if none explicitly passed to us here
     FS.createStandardStreams(input, output, error);
@@ -2717,14 +2717,14 @@ var FS = {
       }
     }
   },
-  findObject(path, dontResolveLastLink) {
+  findObject(path, dontResolveLastLink = false) {
     var ret = FS.analyzePath(path, dontResolveLastLink);
     if (!ret.exists) {
       return null;
     }
     return ret.object;
   },
-  analyzePath(path, dontResolveLastLink) {
+  analyzePath(path, dontResolveLastLink = false) {
     // operate from within the context of the symlink's target
     try {
       var lookup = FS.lookupPath(path, {
@@ -2764,7 +2764,7 @@ var FS = {
     }
     return ret;
   },
-  createPath(parent, path, canRead, canWrite) {
+  createPath(parent, path, canRead = undefined, canWrite = undefined) {
     parent = typeof parent == "string" ? parent : FS.getPath(parent);
     var parts = path.split("/").reverse();
     while (parts.length) {
@@ -2780,12 +2780,12 @@ var FS = {
     }
     return current;
   },
-  createFile(parent, name, properties, canRead, canWrite) {
+  createFile(parent, name, properties, canRead = undefined, canWrite = undefined) {
     var path = PATH.join2(typeof parent == "string" ? parent : FS.getPath(parent), name);
     var mode = FS_getMode(canRead, canWrite);
     return FS.create(path, mode);
   },
-  createDataFile(parent, name, data, canRead, canWrite, canOwn) {
+  createDataFile(parent, name, data = undefined, canRead = undefined, canWrite = undefined, canOwn = undefined) {
     var path = name;
     if (parent) {
       parent = typeof parent == "string" ? parent : FS.getPath(parent);
@@ -2803,7 +2803,7 @@ var FS = {
       FS.chmod(node, mode);
     }
   },
-  createDevice(parent, name, input, output) {
+  createDevice(parent, name, input = undefined, output = undefined) {
     var path = PATH.join2(typeof parent == "string" ? parent : FS.getPath(parent), name);
     var mode = FS_getMode(!!input, !!output);
     FS.createDevice.major ??= 64;
@@ -2870,7 +2870,7 @@ var FS = {
       }
     }
   },
-  createLazyFile(parent, name, url, canRead, canWrite) {
+  createLazyFile(parent, name, url, canRead = undefined, canWrite = undefined) {
     // Lazy chunked Uint8Array (implements get and length from Uint8Array).
     // Actual getting is abstracted away for eventual reuse.
     class LazyUint8Array {
@@ -3058,7 +3058,7 @@ var FS = {
 
 var SYSCALLS = {
   currentUmask: 18,
-  calculateAt(dirfd, path, allowEmpty) {
+  calculateAt(dirfd, path, allowEmpty = false) {
     if (PATH.isAbs(path)) {
       return path;
     }
diff --git a/test/codesize/test_codesize_file_preload.json b/test/codesize/test_codesize_file_preload.json
index 8a288445877b2..7cfc9c75e04ed 100644
--- a/test/codesize/test_codesize_file_preload.json
+++ b/test/codesize/test_codesize_file_preload.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 22203,
-  "a.out.js.gz": 9267,
+  "a.out.js": 22197,
+  "a.out.js.gz": 9262,
   "a.out.nodebug.wasm": 1198,
   "a.out.nodebug.wasm.gz": 730,
-  "total": 23401,
-  "total_gz": 9997,
+  "total": 23395,
+  "total_gz": 9992,
   "sent": [
     "a (fd_write)"
   ],
diff --git a/test/codesize/test_codesize_files_js_fs.json b/test/codesize/test_codesize_files_js_fs.json
index 0c033a7242071..ad9375c481336 100644
--- a/test/codesize/test_codesize_files_js_fs.json
+++ b/test/codesize/test_codesize_files_js_fs.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 17871,
-  "a.out.js.gz": 7460,
+  "a.out.js": 17865,
+  "a.out.js.gz": 7456,
   "a.out.nodebug.wasm": 381,
   "a.out.nodebug.wasm.gz": 258,
-  "total": 18252,
-  "total_gz": 7718,
+  "total": 18246,
+  "total_gz": 7714,
   "sent": [
     "a (fd_write)",
     "b (fd_read)",
diff --git a/test/codesize/test_codesize_hello_dylink.json b/test/codesize/test_codesize_hello_dylink.json
index 842afdc14b16f..499eb271e3266 100644
--- a/test/codesize/test_codesize_hello_dylink.json
+++ b/test/codesize/test_codesize_hello_dylink.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 26188,
-  "a.out.js.gz": 11168,
+  "a.out.js": 26182,
+  "a.out.js.gz": 11167,
   "a.out.nodebug.wasm": 16985,
   "a.out.nodebug.wasm.gz": 8674,
-  "total": 43173,
-  "total_gz": 19842,
+  "total": 43167,
+  "total_gz": 19841,
   "sent": [
     "__syscall_stat64",
     "emscripten_resize_heap",
diff --git a/test/codesize/test_codesize_hello_dylink_all.json b/test/codesize/test_codesize_hello_dylink_all.json
index ecc5f257dc567..ef38223fdd62f 100644
--- a/test/codesize/test_codesize_hello_dylink_all.json
+++ b/test/codesize/test_codesize_hello_dylink_all.json
@@ -1,7 +1,7 @@
 {
-  "a.out.js": 270695,
+  "a.out.js": 270743,
   "a.out.nodebug.wasm": 588098,
-  "total": 858793,
+  "total": 858841,
   "sent": [
     "IMG_Init",
     "IMG_Load",
diff --git a/test/test_other.py b/test/test_other.py
index b755d7b681b5f..9aaeb40412bb5 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -12419,6 +12419,27 @@ def test_closure_warnings(self, flags, outcome):
       else:
         self.assertContained(outcome, proc.stderr)
 
+  @parameterized({
+    '': ([],),
+    'nodefs_sockfs': (['-lnodefs.js', '-lsockfs.js'],),
+  })
+  def test_closure_fs_es6(self, args):
+    # TODO: Delete this test once test_closure_full_js_library can run with
+    # -sEXPORT_ES6. Currently -sINCLUDE_FULL_LIBRARY + -sEXPORT_ES6 fails due
+    # to Closure internal compiler errors (JSC_ILLEGAL_MODULE_RENAMING_CONFLICT):
+    # https://github.com/google/closure-compiler/issues/4344
+    self.build('hello_world.c', output_suffix='.mjs', cflags=[
+      '-O2',
+      '-sEXPORT_ES6',
+      '-sFORCE_FILESYSTEM',
+      '--closure=1',
+    ] + args)
+    create_file('run.mjs', '''
+      import Module from './hello_world.mjs';
+      await Module();
+    ''')
+    self.assertContained('Hello, world!\n', self.run_js('run.mjs'))
+
   def test_bitcode_input(self):
     # Verify that bitcode files are accepted as input
     create_file('main.c', 'void foo(); int main() { return 0; }')