diff -r 0f10e0b3e76d Doc/library/sys.rst
--- a/Doc/library/sys.rst	Thu Oct 01 00:53:09 2015 +0200
+++ b/Doc/library/sys.rst	Thu Oct 01 01:15:06 2015 +0200
@@ -124,6 +124,14 @@ always available.
       defined here, and may change.
 
 
+.. data:: debug_build
+
+   :const:`True` if the Python executable was compiled in debug mode,
+   :const:`False` if it was compiled in release mode.
+
+   .. versionadded:: 3.6
+
+
 .. data:: dllhandle
 
    Integer specifying the handle of the Python DLL. Availability: Windows.
diff -r 0f10e0b3e76d Doc/whatsnew/3.6.rst
--- a/Doc/whatsnew/3.6.rst	Thu Oct 01 00:53:09 2015 +0200
+++ b/Doc/whatsnew/3.6.rst	Thu Oct 01 01:15:06 2015 +0200
@@ -102,6 +102,11 @@ operator
   indexers. For example: ``subscript[0:10:2] == slice(0, 10, 2)``
   (Contributed by Joe Jevnik in :issue:`24379`.)
 
+operator
+--------
+
+* New variable :data:`sys.debug_build`: :const:`True` if the Python executable
+  was compiled in debug mode, `False` if it was compiled in release mode.
 
 rlcomplete
 ----------
diff -r 0f10e0b3e76d Lib/distutils/command/build.py
--- a/Lib/distutils/command/build.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/distutils/command/build.py	Thu Oct 01 01:15:06 2015 +0200
@@ -86,7 +86,7 @@ class build(Command):
         # Make it so Python 2.x and Python 2.x with --with-pydebug don't
         # share the same build directories. Doing so confuses the build
         # process for C modules
-        if hasattr(sys, 'gettotalrefcount'):
+        if sys.debug_build:
             plat_specifier += '-pydebug'
 
         # 'build_purelib' and 'build_platlib' just default to 'lib' and
diff -r 0f10e0b3e76d Lib/distutils/tests/test_build.py
--- a/Lib/distutils/tests/test_build.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/distutils/tests/test_build.py	Thu Oct 01 01:15:06 2015 +0200
@@ -28,7 +28,7 @@ class BuildTestCase(support.TempdirManag
         # examples:
         #   build/lib.macosx-10.3-i386-2.7
         plat_spec = '.%s-%s' % (cmd.plat_name, sys.version[0:3])
-        if hasattr(sys, 'gettotalrefcount'):
+        if sys.debug_build:
             self.assertTrue(cmd.build_platlib.endswith('-pydebug'))
             plat_spec += '-pydebug'
         wanted = os.path.join(cmd.build_base, 'lib' + plat_spec)
diff -r 0f10e0b3e76d Lib/sysconfig.py
--- a/Lib/sysconfig.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/sysconfig.py	Thu Oct 01 01:15:06 2015 +0200
@@ -382,7 +382,7 @@ def _generate_posix_vars():
         sys.modules[name] = module
 
     pybuilddir = 'build/lib.%s-%s' % (get_platform(), sys.version[:3])
-    if hasattr(sys, "gettotalrefcount"):
+    if sys.debug_build:
         pybuilddir += '-pydebug'
     os.makedirs(pybuilddir, exist_ok=True)
     destfile = os.path.join(pybuilddir, name + '.py')
diff -r 0f10e0b3e76d Lib/test/libregrtest/refleak.py
--- a/Lib/test/libregrtest/refleak.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/libregrtest/refleak.py	Thu Oct 01 01:15:06 2015 +0200
@@ -16,7 +16,7 @@ def dash_R(the_module, test, indirect_te
     import copyreg
     import collections.abc
 
-    if not hasattr(sys, 'gettotalrefcount'):
+    if not sys.debug_build:
         raise Exception("Tracking reference leaks requires a debug build "
                         "of Python")
 
diff -r 0f10e0b3e76d Lib/test/support/__init__.py
--- a/Lib/test/support/__init__.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/support/__init__.py	Thu Oct 01 01:15:06 2015 +0200
@@ -1446,7 +1446,7 @@ def python_is_optimized():
 
 _header = 'nP'
 _align = '0n'
-if hasattr(sys, "gettotalrefcount"):
+if sys.debug_build:
     _header = '2P' + _header
     _align = '0P'
 _vheader = _header + 'n'
diff -r 0f10e0b3e76d Lib/test/test_capi.py
--- a/Lib/test/test_capi.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_capi.py	Thu Oct 01 01:15:06 2015 +0200
@@ -23,9 +23,6 @@ except ImportError:
 # Skip this test if the _testcapi module isn't available.
 _testcapi = support.import_module('_testcapi')
 
-# Were we compiled --with-pydebug or with #define Py_DEBUG?
-Py_DEBUG = hasattr(sys, 'gettotalrefcount')
-
 
 def testfunction(self):
     """some doc"""
@@ -179,7 +176,7 @@ class CAPITest(unittest.TestCase):
     def test_return_null_without_error(self):
         # Issue #23571: A function must not return NULL without setting an
         # error
-        if Py_DEBUG:
+        if sys.debug_build:
             code = textwrap.dedent("""
                 import _testcapi
                 from test import support
@@ -206,7 +203,7 @@ class CAPITest(unittest.TestCase):
 
     def test_return_result_with_error(self):
         # Issue #23571: A function must not return a result with an error set
-        if Py_DEBUG:
+        if sys.debug_build:
             code = textwrap.dedent("""
                 import _testcapi
                 from test import support
diff -r 0f10e0b3e76d Lib/test/test_cmd_line.py
--- a/Lib/test/test_cmd_line.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_cmd_line.py	Thu Oct 01 01:15:06 2015 +0200
@@ -96,7 +96,7 @@ class CmdLineTest(unittest.TestCase):
         # "-X showrefcount" shows the refcount, but only in debug builds
         rc, out, err = run_python('-X', 'showrefcount', '-c', code)
         self.assertEqual(out.rstrip(), b"{'showrefcount': True}")
-        if hasattr(sys, 'gettotalrefcount'):  # debug build
+        if sys.debug_build:
             self.assertRegex(err, br'^\[\d+ refs, \d+ blocks\]')
         else:
             self.assertEqual(err, b'')
diff -r 0f10e0b3e76d Lib/test/test_hashlib.py
--- a/Lib/test/test_hashlib.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_hashlib.py	Thu Oct 01 01:15:06 2015 +0200
@@ -20,9 +20,6 @@ import warnings
 from test import support
 from test.support import _4G, bigmemtest, import_fresh_module
 
-# Were we compiled --with-pydebug or with #define Py_DEBUG?
-COMPILED_WITH_PYDEBUG = hasattr(sys, 'gettotalrefcount')
-
 c_hashlib = import_fresh_module('hashlib', fresh=['_hashlib'])
 py_hashlib = import_fresh_module('hashlib', blocked=['_hashlib'])
 
@@ -41,7 +38,7 @@ class HashLibTestCase(unittest.TestCase)
                              'sha384', 'SHA384', 'sha512', 'SHA512')
 
     # Issue #14693: fallback modules are always compiled under POSIX
-    _warn_on_extension_import = os.name == 'posix' or COMPILED_WITH_PYDEBUG
+    _warn_on_extension_import = os.name == 'posix' or sys.debug_build
 
     def _conditional_import_module(self, module_name):
         """Import a module and return a reference to it or None on failure."""
diff -r 0f10e0b3e76d Lib/test/test_marshal.py
--- a/Lib/test/test_marshal.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_marshal.py	Thu Oct 01 01:15:06 2015 +0200
@@ -192,7 +192,7 @@ class BugsTestCase(unittest.TestCase):
         # Create a deeply nested structure.
         head = last = []
         # The max stack depth should match the value in Python/marshal.c.
-        if os.name == 'nt' and hasattr(sys, 'gettotalrefcount'):
+        if os.name == 'nt' and sys.debug_build:
             MAX_MARSHAL_STACK_DEPTH = 1000
         else:
             MAX_MARSHAL_STACK_DEPTH = 2000
diff -r 0f10e0b3e76d Lib/test/test_regrtest.py
--- a/Lib/test/test_regrtest.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_regrtest.py	Thu Oct 01 01:15:06 2015 +0200
@@ -494,7 +494,7 @@ class ProgramsTestCase(BaseTestCase):
         test_args = []
         if platform.architecture()[0] == '64bit':
             test_args.append('-x64')   # 64-bit build
-        if not Py_DEBUG:
+        if not sys.debug_build:
             test_args.append('+d')     # Release build, use python.exe
         self.run_batch(script, *test_args, *self.tests)
 
@@ -505,7 +505,7 @@ class ProgramsTestCase(BaseTestCase):
         rt_args = ["-q"]             # Quick, don't run tests twice
         if platform.architecture()[0] == '64bit':
             rt_args.append('-x64')   # 64-bit build
-        if Py_DEBUG:
+        if sys.debug_build:
             rt_args.append('-d')     # Debug build, use python_d.exe
         self.run_batch(script, *rt_args, *self.regrtest_args, *self.tests)
 
diff -r 0f10e0b3e76d Lib/test/test_sys.py
--- a/Lib/test/test_sys.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/test/test_sys.py	Thu Oct 01 01:15:06 2015 +0200
@@ -769,6 +769,15 @@ class SysModuleTest(unittest.TestCase):
         rc, stdout, stderr = assert_python_ok('-c', code)
         self.assertEqual(stdout.rstrip(), b'True')
 
+    def test_debug_build(self):
+        self.assertIsInstance(sys.debug_build, bool)
+
+    @test.support.cpython_only
+    def test_debug_build_cpython(self):
+        self.assertEqual(sys.debug_build,
+                         # Py_DEBUG implies Py_TRACE_REFS
+                         hasattr(sys, 'getobjects'))
+
 
 @test.support.cpython_only
 class SizeofTest(unittest.TestCase):
diff -r 0f10e0b3e76d Lib/warnings.py
--- a/Lib/warnings.py	Thu Oct 01 00:53:09 2015 +0200
+++ b/Lib/warnings.py	Thu Oct 01 01:15:06 2015 +0200
@@ -426,7 +426,7 @@ if not _warnings_defaults:
         bytes_action = "ignore"
     simplefilter(bytes_action, category=BytesWarning, append=1)
     # resource usage warnings are enabled by default in pydebug mode
-    if hasattr(sys, 'gettotalrefcount'):
+    if sys.debug_build:
         resource_action = "always"
     else:
         resource_action = "ignore"
diff -r 0f10e0b3e76d Python/sysmodule.c
--- a/Python/sysmodule.c	Thu Oct 01 00:53:09 2015 +0200
+++ b/Python/sysmodule.c	Thu Oct 01 01:15:06 2015 +0200
@@ -1795,6 +1795,12 @@ PyObject *
                         PyLong_FromLong(0x10FFFF));
     SET_SYS_FROM_STRING("builtin_module_names",
                         list_builtin_module_names());
+#ifdef Py_DEBUG
+    SET_SYS_FROM_STRING("debug_build", PyBool_FromLong(1));
+#else
+    SET_SYS_FROM_STRING("debug_build", PyBool_FromLong(0));
+#endif
+
 #if PY_BIG_ENDIAN
     SET_SYS_FROM_STRING("byteorder",
                         PyUnicode_FromString("big"));