diff --git a/lib/_http_common.js b/lib/_http_common.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const FreeList = require('freelist').FreeList;
+const FreeList = require('internal/freelist').FreeList;
 const HTTPParser = process.binding('http_parser').HTTPParser;
 
 const incoming = require('_http_incoming');

diff --git a/lib/freelist.js b/lib/freelist.js
@@ -1,26 +1,3 @@
 'use strict';
 
-// This is a free list to avoid creating so many of the same object.
-exports.FreeList = function(name, max, constructor) {
-  this.name = name;
-  this.constructor = constructor;
-  this.max = max;
-  this.list = [];
-};
-
-
-exports.FreeList.prototype.alloc = function() {
-  //debug("alloc " + this.name + " " + this.list.length);
-  return this.list.length ? this.list.shift() :
-                            this.constructor.apply(this, arguments);
-};
-
-
-exports.FreeList.prototype.free = function(obj) {
-  //debug("free " + this.name + " " + this.list.length);
-  if (this.list.length < this.max) {
-    this.list.push(obj);
-    return true;
-  }
-  return false;
-};
+module.exports = require('internal/freelist');
diff --git a/lib/internal/freelist.js b/lib/internal/freelist.js
@@ -0,0 +1,24 @@
+'use strict';
+
+// This is a free list to avoid creating so many of the same object.
+exports.FreeList = function(name, max, constructor) {
+  this.name = name;
+  this.constructor = constructor;
+  this.max = max;
+  this.list = [];
+};
+
+
+exports.FreeList.prototype.alloc = function() {
+  return this.list.length ? this.list.shift() :
+                            this.constructor.apply(this, arguments);
+};
+
+
+exports.FreeList.prototype.free = function(obj) {
+  if (this.list.length < this.max) {
+    this.list.push(obj);
+    return true;
+  }
+  return false;
+};
diff --git a/lib/module.js b/lib/module.js
@@ -200,7 +200,7 @@ Module._nodeModulePaths = function(from) {
 
 
 Module._resolveLookupPaths = function(request, parent) {
-  if (NativeModule.exists(request)) {
+  if (NativeModule.nonInternalExists(request)) {
     return [request, []];
   }
 
@@ -262,7 +262,7 @@ Module._load = function(request, parent, isMain) {
     return cachedModule.exports;
   }
 
-  if (NativeModule.exists(filename)) {
+  if (NativeModule.nonInternalExists(filename)) {
     // REPL is a special case, because it needs the real require.
     if (filename == 'repl') {
       var replModule = new Module('repl');
@@ -299,7 +299,7 @@ Module._load = function(request, parent, isMain) {
 };
 
 Module._resolveFilename = function(request, parent) {
-  if (NativeModule.exists(request)) {
+  if (NativeModule.nonInternalExists(request)) {
     return request;
   }
 

diff --git a/node.gyp b/node.gyp
@@ -69,6 +69,8 @@
       'lib/v8.js',
       'lib/vm.js',
       'lib/zlib.js',
+
+      'lib/internal/freelist.js',
     ],
   },
 

diff --git a/src/node.cc b/src/node.cc
@@ -3133,6 +3133,9 @@ static void ParseArgs(int* argc,
     } else if (strncmp(arg, "--icu-data-dir=", 15) == 0) {
       icu_data_dir = arg + 15;
 #endif
+    } else if (strcmp(arg, "--expose-internals") == 0 ||
+               strcmp(arg, "--expose_internals") == 0) {
+      // consumed in js
     } else {
       // V8 option.  Pass through as-is.
       new_v8_argv[new_v8_argc] = arg;

diff --git a/src/node.js b/src/node.js
@@ -838,6 +838,27 @@
     return NativeModule._source.hasOwnProperty(id);
   };
 
+  const EXPOSE_INTERNALS = process.execArgv.some(function(arg) {
+    return arg.match(/^--expose[-_]internals$/);
+  });
+
+  if (EXPOSE_INTERNALS) {
+    NativeModule.nonInternalExists = NativeModule.exists;
+
+    NativeModule.isInternal = function(id) {
+      return false;
+    };
+  } else {
+    NativeModule.nonInternalExists = function(id) {
+      return NativeModule.exists(id) && !NativeModule.isInternal(id);
+    };
+
+    NativeModule.isInternal = function(id) {
+      return id.startsWith('internal/');
+    };
+  }
+
+
   NativeModule.getSource = function(id) {
     return NativeModule._source[id];
   };

diff --git a/test/fixtures/internal-modules/index.js b/test/fixtures/internal-modules/index.js
@@ -0,0 +1 @@
+module.exports = require('internal/freelist');
diff --git a/test/fixtures/internal-modules/node_modules/internal/freelist.js b/test/fixtures/internal-modules/node_modules/internal/freelist.js
diff --git a/test/parallel/test-internal-modules-expose.js b/test/parallel/test-internal-modules-expose.js
@@ -0,0 +1,6 @@
+// Flags: --expose_internals
+
+var common = require('../common');
+var assert = require('assert');
+
+assert.equal(typeof require('internal/freelist').FreeList, 'function');
diff --git a/test/parallel/test-internal-modules.js b/test/parallel/test-internal-modules.js
@@ -0,0 +1,8 @@
+var common = require('../common');
+var assert = require('assert');
+
+assert.throws(function() {
+  require('internal/freelist');
+});
+
+assert(require('../fixtures/internal-modules') === 42);
diff --git a/tools/js2c.py b/tools/js2c.py
@@ -238,11 +238,11 @@ def ReadMacros(lines):
 
 
 NATIVE_DECLARATION = """\
-  { "%(id)s", %(id)s_native, sizeof(%(id)s_native)-1 },
+  { "%(id)s", %(escaped_id)s_native, sizeof(%(escaped_id)s_native)-1 },
 """
 
 SOURCE_DECLARATION = """\
-  const char %(id)s_native[] = { %(data)s };
+  const char %(escaped_id)s_native[] = { %(data)s };
 """
 
 
@@ -293,16 +293,29 @@ def JS2C(source, target):
     lines = ExpandMacros(lines, macros)
     lines = CompressScript(lines, do_jsmin)
     data = ToCArray(s, lines)
-    id = os.path.basename(str(s)).split('.')[0]
+    id = '/'.join(re.split('/|\\\\', s)[1:]).split('.')[0]
     if delay: id = id[:-6]
     if delay:
       delay_ids.append((id, len(lines)))
     else:
       ids.append((id, len(lines)))
-    source_lines.append(SOURCE_DECLARATION % { 'id': id, 'data': data })
-    source_lines_empty.append(SOURCE_DECLARATION % { 'id': id, 'data': 0 })
-    native_lines.append(NATIVE_DECLARATION % { 'id': id })
-
+
+    escaped_id = id.replace('/', '$')
+    source_lines.append(SOURCE_DECLARATION % {
+      'id': id,
+      'escaped_id': escaped_id,
+      'data': data
+    })
+    source_lines_empty.append(SOURCE_DECLARATION % {
+      'id': id,
+      'escaped_id': escaped_id,
+      'data': 0
+    })
+    native_lines.append(NATIVE_DECLARATION % {
+      'id': id,
+      'escaped_id': escaped_id
+    })
+
   # Build delay support functions
   get_index_cases = [ ]
   get_script_source_cases = [ ]
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		module.exports = require('internal/freelist');
bnoordhuis Mar 13, 2015 Copy link Copy Markdown Member Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Shouldn't this file be called freelist.js or something? Avoids unnecessary churn when another module is added. All reactions vkurchatkin Mar 13, 2015 Copy link Copy Markdown Contributor Author Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Not sure what do you mean. js2c drops extensions so this is how we require internal modules. This particular test checks that if we try it in userland module and there is node_modules/internal/freelist.js everything works as before. All reactions bnoordhuis Mar 13, 2015 Copy link Copy Markdown Member Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality The directory is called test/fixtures/internal-modules but it's really only about the freelist module. Maybe move index.js to test/fixtures/internal-modules/freelist? All reactions vkurchatkin Mar 13, 2015 Copy link Copy Markdown Contributor Author Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality doesn't change a lot. we only need to test this once with any module. it could be anything other than freelist All reactions