diff --git a/Include/internal/pystate.h b/Include/internal/pystate.h
index 516f829ac32..67b4a516a76 100644
--- a/Include/internal/pystate.h
+++ b/Include/internal/pystate.h
@@ -90,7 +90,7 @@ PyAPI_FUNC(_PyInitError) _PyRuntime_Initialize(void);
 
 /* Other */
 
-PyAPI_FUNC(void) _PyInterpreterState_Enable(_PyRuntimeState *);
+PyAPI_FUNC(_PyInitError) _PyInterpreterState_Enable(_PyRuntimeState *);
 
 #ifdef __cplusplus
 }
diff --git a/Include/pydebug.h b/Include/pydebug.h
index 6e23a896c3d..d3b95966aa6 100644
--- a/Include/pydebug.h
+++ b/Include/pydebug.h
@@ -25,6 +25,7 @@ PyAPI_DATA(int) Py_HashRandomizationFlag;
 PyAPI_DATA(int) Py_IsolatedFlag;
 
 #ifdef MS_WINDOWS
+PyAPI_DATA(int) Py_LegacyWindowsFSEncodingFlag;
 PyAPI_DATA(int) Py_LegacyWindowsStdioFlag;
 #endif
 
diff --git a/Include/pystate.h b/Include/pystate.h
index 93815850f3b..440122588f4 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -30,9 +30,20 @@ typedef struct {
     unsigned long hash_seed;
     int _disable_importlib; /* Needed by freeze_importlib */
     char *allocator;
+    int faulthandler;
+    int tracemalloc;        /* Number of saved frames, 0=don't trace */
+    int importtime;         /* -X importtime */
 } _PyCoreConfig;
 
-#define _PyCoreConfig_INIT {0, -1, 0, 0, NULL}
+#define _PyCoreConfig_INIT \
+    {.ignore_environment = 0, \
+     .use_hash_seed = -1, \
+     .hash_seed = 0, \
+     ._disable_importlib = 0, \
+     .allocator = NULL, \
+     .faulthandler = 0, \
+     .tracemalloc = 0, \
+     .importtime = 0}
 
 /* Placeholders while working on the new configuration API
  *
diff --git a/Lib/test/test_tracemalloc.py b/Lib/test/test_tracemalloc.py
index 780942a8061..533ba6dc460 100644
--- a/Lib/test/test_tracemalloc.py
+++ b/Lib/test/test_tracemalloc.py
@@ -829,16 +829,23 @@ class TestCommandLine(unittest.TestCase):
         stdout = stdout.rstrip()
         self.assertEqual(stdout, b'10')
 
+    def check_env_var_invalid(self, nframe):
+        with support.SuppressCrashReport():
+            ok, stdout, stderr = assert_python_failure(
+                '-c', 'pass',
+                PYTHONTRACEMALLOC=str(nframe))
+
+        if b'ValueError: the number of frames must be in range' in stderr:
+            return
+        if b'PYTHONTRACEMALLOC: invalid number of frames' in stderr:
+            return
+        self.fail(f"unexpeced output: {stderr!a}")
+
+
     def test_env_var_invalid(self):
         for nframe in (-1, 0, 2**30):
             with self.subTest(nframe=nframe):
-                with support.SuppressCrashReport():
-                    ok, stdout, stderr = assert_python_failure(
-                        '-c', 'pass',
-                        PYTHONTRACEMALLOC=str(nframe))
-                    self.assertIn(b'PYTHONTRACEMALLOC: invalid '
-                                  b'number of frames',
-                                  stderr)
+                self.check_env_var_invalid(nframe)
 
     def test_sys_xoptions(self):
         for xoptions, nframe in (
@@ -852,15 +859,21 @@ class TestCommandLine(unittest.TestCase):
                 stdout = stdout.rstrip()
                 self.assertEqual(stdout, str(nframe).encode('ascii'))
 
+    def check_sys_xoptions_invalid(self, nframe):
+        args = ('-X', 'tracemalloc=%s' % nframe, '-c', 'pass')
+        with support.SuppressCrashReport():
+            ok, stdout, stderr = assert_python_failure(*args)
+
+        if b'ValueError: the number of frames must be in range' in stderr:
+            return
+        if b'-X tracemalloc=NFRAME: invalid number of frames' in stderr:
+            return
+        self.fail(f"unexpeced output: {stderr!a}")
+
     def test_sys_xoptions_invalid(self):
         for nframe in (-1, 0, 2**30):
             with self.subTest(nframe=nframe):
-                with support.SuppressCrashReport():
-                    args = ('-X', 'tracemalloc=%s' % nframe, '-c', 'pass')
-                    ok, stdout, stderr = assert_python_failure(*args)
-                    self.assertIn(b'-X tracemalloc=NFRAME: invalid '
-                                  b'number of frames',
-                                  stderr)
+                self.check_sys_xoptions_invalid(nframe)
 
     @unittest.skipIf(_testcapi is None, 'need _testcapi')
     def test_pymem_alloc0(self):
diff --git a/Modules/_tracemalloc.c b/Modules/_tracemalloc.c
index af2a2fa4d52..e07022cce2b 100644
--- a/Modules/_tracemalloc.c
+++ b/Modules/_tracemalloc.c
@@ -1066,8 +1066,16 @@ tracemalloc_start(int max_nframe)
     PyMemAllocatorEx alloc;
     size_t size;
 
-    if (tracemalloc_init() < 0)
+    if (max_nframe < 1 || max_nframe > MAX_NFRAME) {
+        PyErr_Format(PyExc_ValueError,
+                     "the number of frames must be in range [1; %i]",
+                     (int)MAX_NFRAME);
         return -1;
+    }
+
+    if (tracemalloc_init() < 0) {
+        return -1;
+    }
 
     if (tracemalloc_config.tracing) {
         /* hook already installed: do nothing */
@@ -1500,7 +1508,7 @@ _PyMem_DumpTraceback(int fd, const void *ptr)
 /*[clinic input]
 _tracemalloc.start
 
-    nframe: Py_ssize_t = 1
+    nframe: int = 1
     /
 
 Start tracing Python memory allocations.
@@ -1510,22 +1518,12 @@ trace to nframe.
 [clinic start generated code]*/
 
 static PyObject *
-_tracemalloc_start_impl(PyObject *module, Py_ssize_t nframe)
-/*[clinic end generated code: output=0f558d2079511553 input=997841629cc441cb]*/
+_tracemalloc_start_impl(PyObject *module, int nframe)
+/*[clinic end generated code: output=caae05c23c159d3c input=40d849b5b29d1933]*/
 {
-    int nframe_int;
-
-    if (nframe < 1 || nframe > MAX_NFRAME) {
-        PyErr_Format(PyExc_ValueError,
-                     "the number of frames must be in range [1; %i]",
-                     (int)MAX_NFRAME);
+    if (tracemalloc_start(nframe) < 0) {
         return NULL;
     }
-    nframe_int = Py_SAFE_DOWNCAST(nframe, Py_ssize_t, int);
-
-    if (tracemalloc_start(nframe_int) < 0)
-        return NULL;
-
     Py_RETURN_NONE;
 }
 
@@ -1658,87 +1656,13 @@ PyInit__tracemalloc(void)
 }
 
 
-static int
-parse_sys_xoptions(PyObject *value)
-{
-    PyObject *valuelong;
-    long nframe;
-
-    if (value == Py_True)
-        return 1;
-
-    assert(PyUnicode_Check(value));
-    if (PyUnicode_GetLength(value) == 0)
-        return -1;
-
-    valuelong = PyLong_FromUnicodeObject(value, 10);
-    if (valuelong == NULL)
-        return -1;
-
-    nframe = PyLong_AsLong(valuelong);
-    Py_DECREF(valuelong);
-    if (nframe == -1 && PyErr_Occurred())
-        return -1;
-
-    if (nframe < 1 || nframe > MAX_NFRAME)
-        return -1;
-
-    return Py_SAFE_DOWNCAST(nframe, long, int);
-}
-
-
 int
-_PyTraceMalloc_Init(void)
+_PyTraceMalloc_Init(int nframe)
 {
-    char *p;
-    int nframe;
-
     assert(PyGILState_Check());
-
-    if ((p = Py_GETENV("PYTHONTRACEMALLOC")) && *p != '\0') {
-        char *endptr = p;
-        long value;
-
-        errno = 0;
-        value = strtol(p, &endptr, 10);
-        if (*endptr != '\0'
-            || value < 1
-            || value > MAX_NFRAME
-            || errno == ERANGE)
-        {
-            Py_FatalError("PYTHONTRACEMALLOC: invalid number of frames");
-            return -1;
-        }
-
-        nframe = (int)value;
+    if (nframe == 0) {
+        return 0;
     }
-    else {
-        PyObject *xoptions, *key, *value;
-
-        xoptions = PySys_GetXOptions();
-        if (xoptions == NULL)
-            return -1;
-
-        key = PyUnicode_FromString("tracemalloc");
-        if (key == NULL)
-            return -1;
-
-        value = PyDict_GetItemWithError(xoptions, key); /* borrowed */
-        Py_DECREF(key);
-        if (value == NULL) {
-            if (PyErr_Occurred())
-                return -1;
-
-            /* -X tracemalloc is not used */
-            return 0;
-        }
-
-        nframe = parse_sys_xoptions(value);
-        if (nframe < 0) {
-            Py_FatalError("-X tracemalloc=NFRAME: invalid number of frames");
-        }
-    }
-
     return tracemalloc_start(nframe);
 }
 
diff --git a/Modules/clinic/_tracemalloc.c.h b/Modules/clinic/_tracemalloc.c.h
index df7b750155e..206dea748be 100644
--- a/Modules/clinic/_tracemalloc.c.h
+++ b/Modules/clinic/_tracemalloc.c.h
@@ -87,15 +87,15 @@ PyDoc_STRVAR(_tracemalloc_start__doc__,
     {"start", (PyCFunction)_tracemalloc_start, METH_FASTCALL, _tracemalloc_start__doc__},
 
 static PyObject *
-_tracemalloc_start_impl(PyObject *module, Py_ssize_t nframe);
+_tracemalloc_start_impl(PyObject *module, int nframe);
 
 static PyObject *
 _tracemalloc_start(PyObject *module, PyObject **args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    Py_ssize_t nframe = 1;
+    int nframe = 1;
 
-    if (!_PyArg_ParseStack(args, nargs, "|n:start",
+    if (!_PyArg_ParseStack(args, nargs, "|i:start",
         &nframe)) {
         goto exit;
     }
@@ -185,4 +185,4 @@ _tracemalloc_get_traced_memory(PyObject *module, PyObject *Py_UNUSED(ignored))
 {
     return _tracemalloc_get_traced_memory_impl(module);
 }
-/*[clinic end generated code: output=c9a0111391b3ec45 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=db4f909464c186e2 input=a9049054013a1b77]*/
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index b6d5aee9b13..0e85cce132f 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -1299,36 +1299,8 @@ faulthandler_init_enable(void)
     return 0;
 }
 
-/* Call faulthandler.enable() if the PYTHONFAULTHANDLER environment variable
-   is defined, or if sys._xoptions has a 'faulthandler' key. */
-
-static int
-faulthandler_init_parse(void)
-{
-    char *p = Py_GETENV("PYTHONFAULTHANDLER");
-    if (p && *p != '\0') {
-        return 1;
-    }
-
-    /* PYTHONFAULTHANDLER environment variable is missing
-       or an empty string */
-    PyObject *xoptions = PySys_GetXOptions();
-    if (xoptions == NULL) {
-        return -1;
-    }
-
-    PyObject *key = PyUnicode_FromString("faulthandler");
-    if (key == NULL) {
-        return -1;
-    }
-
-    int has_key = PyDict_Contains(xoptions, key);
-    Py_DECREF(key);
-    return has_key;
-}
-
 _PyInitError
-_PyFaulthandler_Init(void)
+_PyFaulthandler_Init(int enable)
 {
 #ifdef HAVE_SIGALTSTACK
     int err;
@@ -1357,11 +1329,6 @@ _PyFaulthandler_Init(void)
     PyThread_acquire_lock(thread.cancel_event, 1);
 #endif
 
-    int enable = faulthandler_init_parse();
-    if (enable < 0) {
-        return _Py_INIT_ERR("failed to parse faulthandler env var and cmdline");
-    }
-
     if (enable) {
         if (faulthandler_init_enable() < 0) {
             return _Py_INIT_ERR("failed to enable faulthandler");
diff --git a/Modules/main.c b/Modules/main.c
index 6391ba78d83..95076c642d3 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -111,7 +111,7 @@ static const char usage_6[] =
 "   locale coercion and locale compatibility warnings on stderr.\n";
 
 static void
-usage(int error, const wchar_t* program)
+pymain_usage(int error, const wchar_t* program)
 {
     FILE *f = error ? stderr : stdout;
 
@@ -128,6 +128,20 @@ usage(int error, const wchar_t* program)
     }
 }
 
+
+static char*
+pymain_get_env_var(const char *name)
+{
+    char *var = Py_GETENV(name);
+    if (var && var[0] != '\0') {
+        return var;
+    }
+    else {
+        return NULL;
+    }
+}
+
+
 static void
 pymain_run_statup(PyCompilerFlags *cf)
 {
@@ -444,7 +458,7 @@ pymain_free_impl(_PyMain *pymain)
 static void
 pymain_free(_PyMain *pymain)
 {
-    /* Call pymain_free() with the memory allocator used by pymain_init() */
+    /* Force malloc() memory allocator */
     PyMemAllocatorEx old_alloc, raw_alloc;
     PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
     _PyMem_GetDefaultRawAllocator(&raw_alloc);
@@ -488,11 +502,12 @@ error:
 
 
 static wchar_t*
-pymain_strdup(wchar_t *str)
+pymain_strdup(_PyMain *pymain, wchar_t *str)
 {
     size_t len = wcslen(str) + 1;  /* +1 for NUL character */
     wchar_t *str2 = PyMem_RawMalloc(sizeof(wchar_t) * len);
     if (str2 == NULL) {
+        pymain->err = INIT_NO_MEMORY();
         return NULL;
     }
     memcpy(str2, str, len * sizeof(wchar_t));
@@ -501,9 +516,9 @@ pymain_strdup(wchar_t *str)
 
 
 static int
-pymain_optlist_append(_Py_OptList *list, wchar_t *str)
+pymain_optlist_append(_PyMain *pymain, _Py_OptList *list, wchar_t *str)
 {
-    wchar_t *str2 = pymain_strdup(str);
+    wchar_t *str2 = pymain_strdup(pymain, str);
     if (str2 == NULL) {
         return -1;
     }
@@ -512,6 +527,7 @@ pymain_optlist_append(_Py_OptList *list, wchar_t *str)
     wchar_t **options2 = (wchar_t **)PyMem_RawRealloc(list->options, size);
     if (options2 == NULL) {
         PyMem_RawFree(str2);
+        pymain->err = INIT_NO_MEMORY();
         return -1;
     }
     options2[list->len] = str2;
@@ -526,7 +542,7 @@ pymain_optlist_append(_Py_OptList *list, wchar_t *str)
    Return 1 if parsing failed.
    Set pymain->err and return -1 on other errors. */
 static int
-pymain_parse_cmdline(_PyMain *pymain)
+pymain_parse_cmdline_impl(_PyMain *pymain)
 {
     _Py_CommandLineDetails *cmdline = &pymain->cmdline;
 
@@ -544,7 +560,8 @@ pymain_parse_cmdline(_PyMain *pymain)
             size_t len = wcslen(_PyOS_optarg) + 1 + 1;
             wchar_t *command = PyMem_RawMalloc(sizeof(wchar_t) * len);
             if (command == NULL) {
-                goto out_of_memory;
+                pymain->err = INIT_NO_MEMORY();
+                return -1;
             }
             memcpy(command, _PyOS_optarg, len * sizeof(wchar_t));
             command[len - 2] = '\n';
@@ -629,16 +646,16 @@ pymain_parse_cmdline(_PyMain *pymain)
             break;
 
         case 'W':
-            if (pymain_optlist_append(&cmdline->warning_options,
+            if (pymain_optlist_append(pymain, &cmdline->warning_options,
                                       _PyOS_optarg) < 0) {
-                goto out_of_memory;
+                return -1;
             }
             break;
 
         case 'X':
-            if (pymain_optlist_append(&cmdline->xoptions,
+            if (pymain_optlist_append(pymain, &cmdline->xoptions,
                                       _PyOS_optarg) < 0) {
-                goto out_of_memory;
+                return -1;
             }
             break;
 
@@ -666,10 +683,6 @@ pymain_parse_cmdline(_PyMain *pymain)
     }
 
     return 0;
-
-out_of_memory:
-    pymain->err = INIT_NO_MEMORY();
-    return -1;
 }
 
 
@@ -753,17 +766,18 @@ pymain_warnings_envvar(_PyMain *pymain)
 
         buf = (wchar_t *)PyMem_RawMalloc((wcslen(wp) + 1) * sizeof(wchar_t));
         if (buf == NULL) {
-            goto out_of_memory;
+            pymain->err = INIT_NO_MEMORY();
+            return -1;
         }
         wcscpy(buf, wp);
         for (warning = wcstok_s(buf, L",", &context);
              warning != NULL;
              warning = wcstok_s(NULL, L",", &context)) {
 
-            if (pymain_optlist_append(&pymain->env_warning_options,
+            if (pymain_optlist_append(pymain, &pymain->env_warning_options,
                                       warning) < 0) {
                 PyMem_RawFree(buf);
-                goto out_of_memory;
+                return -1;
             }
         }
         PyMem_RawFree(buf);
@@ -778,7 +792,8 @@ pymain_warnings_envvar(_PyMain *pymain)
            C89 wcstok */
         buf = (char *)PyMem_RawMalloc(strlen(p) + 1);
         if (buf == NULL) {
-            goto out_of_memory;
+            pymain->err = INIT_NO_MEMORY();
+            return -1;
         }
         strcpy(buf, p);
         oldloc = _PyMem_RawStrdup(setlocale(LC_ALL, NULL));
@@ -793,13 +808,14 @@ pymain_warnings_envvar(_PyMain *pymain)
                     return -1;
                 }
                 else {
-                    goto out_of_memory;
+                    pymain->err = INIT_NO_MEMORY();
+                    return -1;
                 }
             }
-            if (pymain_optlist_append(&pymain->env_warning_options,
+            if (pymain_optlist_append(pymain, &pymain->env_warning_options,
                                       warning) < 0) {
                 PyMem_RawFree(warning);
-                goto out_of_memory;
+                return -1;
             }
             PyMem_RawFree(warning);
         }
@@ -809,10 +825,6 @@ pymain_warnings_envvar(_PyMain *pymain)
     }
 #endif
     return 0;
-
-out_of_memory:
-    pymain->err = INIT_NO_MEMORY();
-    return -1;
 }
 
 
@@ -882,7 +894,8 @@ pymain_get_program_name(_PyMain *pymain)
 
         buffer = PyMem_RawMalloc(len * sizeof(wchar_t));
         if (buffer == NULL) {
-            goto out_of_memory;
+            pymain->err = INIT_NO_MEMORY();
+            return -1;
         }
 
         mbstowcs(buffer, p, len);
@@ -904,7 +917,8 @@ pymain_get_program_name(_PyMain *pymain)
                     return -1;
                 }
                 else {
-                    goto out_of_memory;
+                    pymain->err = INIT_NO_MEMORY();
+                    return -1;
                 }
             }
             pymain->program_name = wbuf;
@@ -915,16 +929,12 @@ pymain_get_program_name(_PyMain *pymain)
 
     if (pymain->program_name == NULL) {
         /* Use argv[0] by default */
-        pymain->program_name = pymain_strdup(pymain->argv[0]);
+        pymain->program_name = pymain_strdup(pymain, pymain->argv[0]);
         if (pymain->program_name == NULL) {
-            goto out_of_memory;
+            return -1;
         }
     }
     return 0;
-
-out_of_memory:
-    pymain->err = INIT_NO_MEMORY();
-    return -1;
 }
 
 
@@ -982,7 +992,7 @@ pymain_header(_PyMain *pymain)
 
 
 static void
-pymain_init_argv(_PyMain *pymain)
+pymain_set_argv(_PyMain *pymain)
 {
     _Py_CommandLineDetails *cmdline = &pymain->cmdline;
 
@@ -999,10 +1009,6 @@ pymain_init_argv(_PyMain *pymain)
         pymain->argv[_PyOS_optind] = L"-m";
     }
 
-    if (cmdline->filename != NULL) {
-        pymain->main_importer_path = pymain_get_importer(cmdline->filename);
-    }
-
     int update_path;
     if (pymain->main_importer_path != NULL) {
         /* Let pymain_run_main_from_importer() adjust sys.path[0] later */
@@ -1039,28 +1045,6 @@ pymain_set_global_config(_PyMain *pymain)
 }
 
 
-/* Propagate options parsed from the command line and environment variables
-   to the Python runtime.
-
-   Return 0 on success, or set pymain->err and return -1 on error. */
-static int
-pymain_configure_pyruntime(_PyMain *pymain)
-{
-    Py_SetProgramName(pymain->program_name);
-    /* Don't free program_name here: the argument to Py_SetProgramName
-       must remain valid until Py_FinalizeEx is called. The string is freed
-       by pymain_free(). */
-
-    if (pymain_add_xoptions(pymain)) {
-        return -1;
-    }
-    if (pymain_add_warnings_options(pymain)) {
-        return -1;
-    }
-    return 0;
-}
-
-
 static void
 pymain_import_readline(_PyMain *pymain)
 {
@@ -1135,7 +1119,7 @@ pymain_open_filename(_PyMain *pymain)
 
 
 static void
-pymain_run(_PyMain *pymain)
+pymain_run_filename(_PyMain *pymain)
 {
     _Py_CommandLineDetails *cmdline = &pymain->cmdline;
 
@@ -1169,24 +1153,22 @@ pymain_run(_PyMain *pymain)
 static void
 pymain_repl(_PyMain *pymain)
 {
-    char *p;
-
     /* Check this environment variable at the end, to give programs the
-     * opportunity to set it from Python.
-     */
-    if (!Py_InspectFlag &&
-        (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0')
-    {
+       opportunity to set it from Python. */
+    if (!Py_InspectFlag && pymain_get_env_var("PYTHONINSPECT")) {
         Py_InspectFlag = 1;
     }
 
-    if (Py_InspectFlag && pymain->stdin_is_interactive && pymain->run_code) {
-        Py_InspectFlag = 0;
-        pymain_run_interactive_hook();
-        /* XXX */
-        int res = PyRun_AnyFileFlags(stdin, "<stdin>", &pymain->cf);
-        pymain->status = (res != 0);
+    if (!(Py_InspectFlag && pymain->stdin_is_interactive
+          && pymain->run_code)) {
+        return;
     }
+
+    Py_InspectFlag = 0;
+    pymain_run_interactive_hook();
+    /* XXX */
+    int res = PyRun_AnyFileFlags(stdin, "<stdin>", &pymain->cf);
+    pymain->status = (res != 0);
 }
 
 
@@ -1197,22 +1179,22 @@ pymain_repl(_PyMain *pymain)
    Return 0 on success.
    Set pymain->err and return -1 on failure. */
 static int
-pymain_init_cmdline(_PyMain *pymain)
+pymain_parse_cmdline(_PyMain *pymain)
 {
     _Py_CommandLineDetails *cmdline = &pymain->cmdline;
 
-    int res = pymain_parse_cmdline(pymain);
+    int res = pymain_parse_cmdline_impl(pymain);
     if (res < 0) {
         return -1;
     }
     if (res) {
-        usage(1, pymain->argv[0]);
+        pymain_usage(1, pymain->argv[0]);
         pymain->status = 2;
         return 1;
     }
 
     if (cmdline->print_help) {
-        usage(0, pymain->argv[0]);
+        pymain_usage(0, pymain->argv[0]);
         pymain->status = 0;
         return 1;
     }
@@ -1230,34 +1212,170 @@ pymain_init_cmdline(_PyMain *pymain)
 }
 
 
-/* Initialize Py_Main().
-   This code must not use Python runtime apart PyMem_Raw memory allocator.
-
-   Return 0 on success.
-   Return 1 if Python is done and must exit.
-   Set pymain->err and return -1 on error. */
-static int
-pymain_init_impl(_PyMain *pymain)
+static wchar_t*
+pymain_get_xoption(_PyMain *pymain, wchar_t *name)
 {
-    _PyCoreConfig *core_config = &pymain->core_config;
-    core_config->_disable_importlib = 0;
+    _Py_OptList *list = &pymain->cmdline.xoptions;
+    for (size_t i=0; i < list->len; i++) {
+        wchar_t *option = list->options[i];
+        size_t len;
+        wchar_t *sep = wcschr(option, L'=');
+        if (sep != NULL) {
+            len = (sep - option);
+        }
+        else {
+            len = wcslen(option);
+        }
+        if (wcsncmp(option, name, len) == 0 && name[len] == L'\0') {
+            return option;
+        }
+    }
+    return NULL;
+}
 
-    orig_argc = pymain->argc;           /* For Py_GetArgcArgv() */
-    orig_argv = pymain->argv;
 
-    /* Parse the command line */
-    int res = pymain_init_cmdline(pymain);
-    if (res < 0) {
+static int
+pymain_str_to_int(char *str, int *result)
+{
+    errno = 0;
+    char *endptr = str;
+    long value = strtol(str, &endptr, 10);
+    if (*endptr != '\0' || errno == ERANGE) {
         return -1;
     }
-    if (res > 0) {
-        return 1;
+    if (value < INT_MIN || value > INT_MAX) {
+        return -1;
     }
 
-    pymain_set_global_config(pymain);
-    pymain_init_stdio(pymain);
+    *result = (int)value;
+    return 0;
+}
+
+
+static int
+pymain_wstr_to_int(wchar_t *wstr, int *result)
+{
+    errno = 0;
+    wchar_t *endptr = wstr;
+    long value = wcstol(wstr, &endptr, 10);
+    if (*endptr != '\0' || errno == ERANGE) {
+        return -1;
+    }
+    if (value < INT_MIN || value > INT_MAX) {
+        return -1;
+    }
+
+    *result = (int)value;
+    return 0;
+}
+
+
+static int
+pymain_init_tracemalloc(_PyMain *pymain)
+{
+    int nframe;
+    int valid;
+
+    char *env = pymain_get_env_var("PYTHONTRACEMALLOC");
+    if (env) {
+        if (!pymain_str_to_int(env, &nframe)) {
+            valid = (nframe >= 1);
+        }
+        else {
+            valid = 0;
+        }
+        if (!valid) {
+            pymain->err = _Py_INIT_USER_ERR("PYTHONTRACEMALLOC: invalid "
+                                            "number of frames");
+            return -1;
+        }
+        pymain->core_config.tracemalloc = nframe;
+    }
+
+    wchar_t *xoption = pymain_get_xoption(pymain, L"tracemalloc");
+    if (xoption) {
+        wchar_t *sep = wcschr(xoption, L'=');
+        if (sep) {
+            if (!pymain_wstr_to_int(sep + 1, &nframe)) {
+                valid = (nframe >= 1);
+            }
+            else {
+                valid = 0;
+            }
+            if (!valid) {
+                pymain->err = _Py_INIT_USER_ERR("-X tracemalloc=NFRAME: "
+                                                "invalid number of frames");
+                return -1;
+            }
+        }
+        else {
+            /* -X tracemalloc behaves as -X tracemalloc=1 */
+            nframe = 1;
+        }
+        pymain->core_config.tracemalloc = nframe;
+    }
+    return 0;
+}
+
+
+static void
+pymain_set_flag_from_env(int *flag, const char *name)
+{
+    char *var = pymain_get_env_var(name);
+    if (!var) {
+        return;
+    }
+    int value;
+    if (pymain_str_to_int(var, &value) < 0 || value < 0) {
+        /* PYTHONDEBUG=text and PYTHONDEBUG=-2 behave as PYTHONDEBUG=1 */
+        value = 1;
+    }
+    if (*flag < value) {
+        *flag = value;
+    }
+}
+
+
+static void
+pymain_set_flags_from_env(_PyMain *pymain)
+{
+    pymain_set_flag_from_env(&Py_DebugFlag,
+                             "PYTHONDEBUG");
+    pymain_set_flag_from_env(&Py_VerboseFlag,
+                             "PYTHONVERBOSE");
+    pymain_set_flag_from_env(&Py_OptimizeFlag,
+                             "PYTHONOPTIMIZE");
+    pymain_set_flag_from_env(&Py_InspectFlag,
+                             "PYTHONINSPECT");
+    pymain_set_flag_from_env(&Py_DontWriteBytecodeFlag,
+                             "PYTHONDONTWRITEBYTECODE");
+    pymain_set_flag_from_env(&Py_NoUserSiteDirectory,
+                             "PYTHONNOUSERSITE");
+    pymain_set_flag_from_env(&Py_UnbufferedStdioFlag,
+                             "PYTHONUNBUFFERED");
+#ifdef MS_WINDOWS
+    pymain_set_flag_from_env(&Py_LegacyWindowsFSEncodingFlag,
+                             "PYTHONLEGACYWINDOWSFSENCODING");
+    pymain_set_flag_from_env(&Py_LegacyWindowsStdioFlag,
+                             "PYTHONLEGACYWINDOWSSTDIO");
+#endif
+}
+
+
+static int
+pymain_parse_envvars(_PyMain *pymain)
+{
+    _PyCoreConfig *core_config = &pymain->core_config;
 
     /* Get environment variables */
+    pymain_set_flags_from_env(pymain);
+
+    /* The variable is only tested for existence here;
+       _Py_HashRandomization_Init will check its value further. */
+    if (pymain_get_env_var("PYTHONHASHSEED")) {
+        Py_HashRandomizationFlag = 1;
+    }
+
     if (pymain_warnings_envvar(pymain) < 0) {
         return -1;
     }
@@ -1266,10 +1384,122 @@ pymain_init_impl(_PyMain *pymain)
     }
     core_config->allocator = Py_GETENV("PYTHONMALLOC");
 
+    /* More complex options: env var and/or -X option */
+    if (pymain_get_env_var("PYTHONFAULTHANDLER")
+       || pymain_get_xoption(pymain, L"faulthandler")) {
+        core_config->faulthandler = 1;
+    }
+    if (pymain_get_env_var("PYTHONPROFILEIMPORTTIME")
+       || pymain_get_xoption(pymain, L"importtime")) {
+        core_config->importtime = 1;
+    }
+    if (pymain_init_tracemalloc(pymain) < 0) {
+        return -1;
+    }
     return 0;
 }
 
 
+/* Parse command line options and environment variables.
+   This code must not use Python runtime apart PyMem_Raw memory allocator.
+
+   Return 0 on success.
+   Return 1 if Python is done and must exit.
+   Set pymain->err and return -1 on error. */
+static int
+pymain_parse_cmdline_envvars_impl(_PyMain *pymain)
+{
+    int res = pymain_parse_cmdline(pymain);
+    if (res < 0) {
+        return -1;
+    }
+    if (res > 0) {
+        return 1;
+    }
+
+    pymain_set_global_config(pymain);
+
+    if (pymain_parse_envvars(pymain) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+
+static int
+pymain_parse_cmdline_envvars(_PyMain *pymain)
+{
+    /* Force malloc() memory allocator */
+    PyMemAllocatorEx old_alloc, raw_alloc;
+    PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+    _PyMem_GetDefaultRawAllocator(&raw_alloc);
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &raw_alloc);
+
+    int res = pymain_parse_cmdline_envvars_impl(pymain);
+
+    /* Restore the old memory allocator */
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    return res;
+}
+
+static int
+pymain_init_python(_PyMain *pymain)
+{
+    pymain_init_stdio(pymain);
+
+    pymain->err = _Py_InitializeCore(&pymain->core_config);
+    if (_Py_INIT_FAILED(pymain->err)) {
+        return -1;
+    }
+
+    Py_SetProgramName(pymain->program_name);
+    /* Don't free program_name here: the argument to Py_SetProgramName
+       must remain valid until Py_FinalizeEx is called. The string is freed
+       by pymain_free(). */
+
+    if (pymain_add_xoptions(pymain)) {
+        return -1;
+    }
+    if (pymain_add_warnings_options(pymain)) {
+        return -1;
+    }
+
+    if (pymain_init_main_interpreter(pymain)) {
+        return -1;
+    }
+    return 0;
+}
+
+
+static void
+pymain_run_python(_PyMain *pymain)
+{
+    _Py_CommandLineDetails *cmdline = &pymain->cmdline;
+
+    pymain_header(pymain);
+    pymain_import_readline(pymain);
+
+    if (cmdline->filename != NULL) {
+        pymain->main_importer_path = pymain_get_importer(cmdline->filename);
+    }
+
+    pymain_set_argv(pymain);
+
+    if (cmdline->command) {
+        pymain->status = pymain_run_command(cmdline->command, &pymain->cf);
+    }
+    else if (cmdline->module) {
+        pymain->status = (pymain_run_module(cmdline->module, 1) != 0);
+    }
+    else {
+        pymain_run_filename(pymain);
+    }
+    pymain_repl(pymain);
+}
+
+
 static int
 pymain_init(_PyMain *pymain)
 {
@@ -1278,61 +1508,43 @@ pymain_init(_PyMain *pymain)
         return -1;
     }
 
-    /* Make sure that all memory allocated in pymain_init() is allocated
-       by malloc() */
-    PyMemAllocatorEx old_alloc, raw_alloc;
-    PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
-    _PyMem_GetDefaultRawAllocator(&raw_alloc);
-    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &raw_alloc);
+    pymain->core_config._disable_importlib = 0;
 
-    int res = pymain_init_impl(pymain);
-
-    /* Restore the old memory allocator */
-    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
-
-    return res;
+    orig_argc = pymain->argc;           /* For Py_GetArgcArgv() */
+    orig_argv = pymain->argv;
+    return 0;
 }
 
+
 static int
-pymain_core(_PyMain *pymain)
+pymain_impl(_PyMain *pymain)
 {
-    _Py_CommandLineDetails *cmdline = &pymain->cmdline;
-
-    pymain->err = _Py_InitializeCore(&pymain->core_config);
-    if (_Py_INIT_FAILED(pymain->err)) {
+    int res = pymain_init(pymain);
+    if (res < 0) {
         return -1;
     }
 
-    if (pymain_configure_pyruntime(pymain)) {
+    res = pymain_parse_cmdline_envvars(pymain);
+    if (res < 0) {
+        return -1;
+    }
+    if (res > 0) {
+        /* --help or --version command: we are done */
+        return 0;
+    }
+
+    res = pymain_init_python(pymain);
+    if (res < 0) {
         return -1;
     }
 
-    if (pymain_init_main_interpreter(pymain)) {
-        return -1;
-    }
-
-    pymain_header(pymain);
-    pymain_import_readline(pymain);
-
-    pymain_init_argv(pymain);
-
-    if (cmdline->command) {
-        pymain->status = pymain_run_command(cmdline->command, &pymain->cf);
-    }
-    else if (cmdline->module) {
-        pymain->status = (pymain_run_module(cmdline->module, 1) != 0);
-    }
-    else {
-        pymain_run(pymain);
-    }
-    pymain_repl(pymain);
+    pymain_run_python(pymain);
 
     if (Py_FinalizeEx() < 0) {
         /* Value unlikely to be confused with a non-error exit status or
-        other special meaning */
+           other special meaning */
         pymain->status = 120;
     }
-
     return 0;
 }
 
@@ -1345,17 +1557,9 @@ Py_Main(int argc, wchar_t **argv)
     pymain.argc = argc;
     pymain.argv = argv;
 
-    int res = pymain_init(&pymain);
-    if (res < 0) {
+    if (pymain_impl(&pymain) < 0) {
         _Py_FatalInitError(pymain.err);
     }
-    if (res == 0) {
-        res = pymain_core(&pymain);
-        if (res < 0) {
-            _Py_FatalInitError(pymain.err);
-        }
-    }
-
     pymain_free(&pymain);
 
     return pymain.status;
diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
index e667fa93f0a..610541d810b 100644
--- a/Python/bootstrap_hash.c
+++ b/Python/bootstrap_hash.c
@@ -594,8 +594,8 @@ init_hash_secret(int use_hash_seed,
            pyurandom() is non-blocking mode (blocking=0): see the PEP 524. */
         res = pyurandom(secret, secret_size, 0, 0);
         if (res < 0) {
-            return _Py_INIT_ERR("failed to get random numbers "
-                                "to initialize Python");
+            return _Py_INIT_USER_ERR("failed to get random numbers "
+                                     "to initialize Python");
         }
     }
     return _Py_INIT_OK();
diff --git a/Python/import.c b/Python/import.c
index fe60844ef18..fef639825c4 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1675,10 +1675,9 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
     }
     else {
         /* 1 -- true, 0 -- false, -1 -- not initialized */
-        static int ximporttime = -1;
+        int importtime = interp->core_config.importtime;
         static int import_level;
         static _PyTime_t accumulated;
-        _Py_IDENTIFIER(importtime);
 
         _PyTime_t t1 = 0, accumulated_copy = accumulated;
 
@@ -1687,32 +1686,14 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
          * Anyway, importlib._find_and_load is much slower than
          * _PyDict_GetItemIdWithError().
          */
-        if (ximporttime < 0) {
-            const char *envoption = Py_GETENV("PYTHONPROFILEIMPORTTIME");
-            if (envoption != NULL && *envoption != '\0') {
-                ximporttime = 1;
-            }
-            else {
-                PyObject *xoptions = PySys_GetXOptions();
-                PyObject *value = NULL;
-                if (xoptions) {
-                    value = _PyDict_GetItemIdWithError(
-                        xoptions, &PyId_importtime);
-                }
-                if (value == NULL && PyErr_Occurred()) {
-                    goto error;
-                }
-                if (value != NULL || Py_IsInitialized()) {
-                    ximporttime = (value == Py_True);
-                }
-            }
-            if (ximporttime > 0) {
+        if (importtime) {
+            static int header = 1;
+            if (header) {
                 fputs("import time: self [us] | cumulative | imported package\n",
                       stderr);
+                header = 0;
             }
-        }
 
-        if (ximporttime > 0) {
             import_level++;
             t1 = _PyTime_GetPerfCounter();
             accumulated = 0;
@@ -1731,7 +1712,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
             PyDTrace_IMPORT_FIND_LOAD_DONE(PyUnicode_AsUTF8(abs_name),
                                            mod != NULL);
 
-        if (ximporttime > 0) {
+        if (importtime) {
             _PyTime_t cum = _PyTime_GetPerfCounter() - t1;
 
             import_level--;
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 66cc711137c..14fe75e0cf7 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -56,7 +56,7 @@ extern grammar _PyParser_Grammar; /* From graminit.c */
 static _PyInitError add_main_module(PyInterpreterState *interp);
 static _PyInitError initfsencoding(PyInterpreterState *interp);
 static _PyInitError initsite(void);
-static int initstdio(void);
+static _PyInitError init_sys_streams(void);
 static _PyInitError initsigs(void);
 static void call_py_exitfuncs(void);
 static void wait_for_thread_shutdown(void);
@@ -66,10 +66,10 @@ extern int _PyStructSequence_Init(void);
 extern void _PyUnicode_Fini(void);
 extern int _PyLong_Init(void);
 extern void PyLong_Fini(void);
-extern _PyInitError _PyFaulthandler_Init(void);
+extern _PyInitError _PyFaulthandler_Init(int enable);
 extern void _PyFaulthandler_Fini(void);
 extern void _PyHash_Fini(void);
-extern int _PyTraceMalloc_Init(void);
+extern int _PyTraceMalloc_Init(int enable);
 extern int _PyTraceMalloc_Fini(void);
 extern void _Py_ReadyTypes(void);
 
@@ -219,20 +219,6 @@ Py_SetStandardStreamEncoding(const char *encoding, const char *errors)
 
 */
 
-static void
-set_flag(int *flag, const char *envs)
-{
-    /* Helper to set flag variables from environment variables:
-    *   - uses the higher of the two values if they're both set
-    *   - otherwise sets the flag to 1
-    */
-    int env = atoi(envs);
-    if (*flag < env)
-        *flag = env;
-    if (*flag < 1)
-        *flag = 1;
-}
-
 static char*
 get_codec_name(const char *encoding)
 {
@@ -284,7 +270,6 @@ get_locale_encoding(void)
 #endif
 }
 
-/* Return NULL on success, or return an error message on failure */
 static _PyInitError
 initimport(PyInterpreterState *interp, PyObject *sysmod)
 {
@@ -346,7 +331,6 @@ initimport(PyInterpreterState *interp, PyObject *sysmod)
     return _Py_INIT_OK();
 }
 
-/* Return NULL on success, or return an error message on failure */
 static _PyInitError
 initexternalimport(PyInterpreterState *interp)
 {
@@ -623,8 +607,6 @@ _Py_SetLocaleFromEnv(int category)
  * Any code invoked from this function should *not* assume it has access
  * to the Python C API (unless the API is explicitly listed as being
  * safe to call without calling Py_Initialize first)
- *
- * Return NULL on success, or return an error message on failure.
  */
 
 /* TODO: Progressively move functionality from Py_BeginInitialization to
@@ -637,7 +619,6 @@ _Py_InitializeCore(const _PyCoreConfig *config)
     PyInterpreterState *interp;
     PyThreadState *tstate;
     PyObject *bimod, *sysmod, *pstderr;
-    char *p;
     _PyCoreConfig core_config = _PyCoreConfig_INIT;
     _PyMainInterpreterConfig preinit_config = _PyMainInterpreterConfig_INIT;
     _PyInitError err;
@@ -681,31 +662,6 @@ _Py_InitializeCore(const _PyCoreConfig *config)
     _emit_stderr_warning_for_legacy_locale();
 #endif
 
-    if ((p = Py_GETENV("PYTHONDEBUG")) && *p != '\0')
-        set_flag(&Py_DebugFlag, p);
-    if ((p = Py_GETENV("PYTHONVERBOSE")) && *p != '\0')
-        set_flag(&Py_VerboseFlag, p);
-    if ((p = Py_GETENV("PYTHONOPTIMIZE")) && *p != '\0')
-        set_flag(&Py_OptimizeFlag, p);
-    if ((p = Py_GETENV("PYTHONINSPECT")) && *p != '\0')
-        set_flag(&Py_InspectFlag, p);
-    if ((p = Py_GETENV("PYTHONDONTWRITEBYTECODE")) && *p != '\0')
-        set_flag(&Py_DontWriteBytecodeFlag, p);
-    if ((p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0')
-        set_flag(&Py_NoUserSiteDirectory, p);
-    if ((p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0')
-        set_flag(&Py_UnbufferedStdioFlag, p);
-    /* The variable is only tested for existence here;
-       _Py_HashRandomization_Init will check its value further. */
-    if ((p = Py_GETENV("PYTHONHASHSEED")) && *p != '\0')
-        set_flag(&Py_HashRandomizationFlag, p);
-#ifdef MS_WINDOWS
-    if ((p = Py_GETENV("PYTHONLEGACYWINDOWSFSENCODING")) && *p != '\0')
-        set_flag(&Py_LegacyWindowsFSEncodingFlag, p);
-    if ((p = Py_GETENV("PYTHONLEGACYWINDOWSSTDIO")) && *p != '\0')
-        set_flag(&Py_LegacyWindowsStdioFlag, p);
-#endif
-
     err = _Py_HashRandomization_Init(&core_config);
     if (_Py_INIT_FAILED(err)) {
         return err;
@@ -716,7 +672,11 @@ _Py_InitializeCore(const _PyCoreConfig *config)
         Py_HashRandomizationFlag = 1;
     }
 
-    _PyInterpreterState_Enable(&_PyRuntime);
+    err = _PyInterpreterState_Enable(&_PyRuntime);
+    if (_Py_INIT_FAILED(err)) {
+        return err;
+    }
+
     interp = PyInterpreterState_New();
     if (interp == NULL)
         return _Py_INIT_ERR("can't make main interpreter");
@@ -834,8 +794,6 @@ _Py_InitializeCore(const _PyCoreConfig *config)
  *
  * More advanced selective initialization tricks are possible by calling
  * this function multiple times with various preconfigured settings.
- *
- * Return NULL on success, or return an error message on failure.
  */
 
 _PyInitError
@@ -858,8 +816,6 @@ _Py_ReadMainInterpreterConfig(_PyMainInterpreterConfig *config)
  * initialized or without a valid current thread state is a fatal error.
  * Other errors should be reported as normal Python exceptions with a
  * non-zero return code.
- *
- * Return NULL on success, or return an error message on failure.
  */
 _PyInitError
 _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
@@ -907,13 +863,14 @@ _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
     PySys_SetPath(Py_GetPath());
     if (_PySys_EndInit(interp->sysdict) < 0)
         return _Py_INIT_ERR("can't finish initializing sys");
+
     err = initexternalimport(interp);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
 
     /* initialize the faulthandler module */
-    err = _PyFaulthandler_Init();
+    err = _PyFaulthandler_Init(interp->core_config.faulthandler);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
@@ -930,15 +887,17 @@ _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
         }
     }
 
-    if (_PyTraceMalloc_Init() < 0)
+    if (_PyTraceMalloc_Init(interp->core_config.tracemalloc) < 0)
         return _Py_INIT_ERR("can't initialize tracemalloc");
 
     err = add_main_module(interp);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
-    if (initstdio() < 0) {
-        return _Py_INIT_ERR("can't initialize sys standard streams");
+
+    err = init_sys_streams();
+    if (_Py_INIT_FAILED(err)) {
+        return err;
     }
 
     /* Initialize warnings. */
@@ -1302,29 +1261,32 @@ Py_Finalize(void)
 
 */
 
-PyThreadState *
-Py_NewInterpreter(void)
+static _PyInitError
+new_interpreter(PyThreadState **tstate_p)
 {
     PyInterpreterState *interp;
     PyThreadState *tstate, *save_tstate;
     PyObject *bimod, *sysmod;
-    _PyInitError err = _Py_INIT_OK();
 
-    if (!_PyRuntime.initialized)
-        Py_FatalError("Py_NewInterpreter: call Py_Initialize first");
+    if (!_PyRuntime.initialized) {
+        return _Py_INIT_ERR("Py_Initialize must be called first");
+    }
 
     /* Issue #10915, #15751: The GIL API doesn't work with multiple
        interpreters: disable PyGILState_Check(). */
     _PyGILState_check_enabled = 0;
 
     interp = PyInterpreterState_New();
-    if (interp == NULL)
-        return NULL;
+    if (interp == NULL) {
+        *tstate_p = NULL;
+        return _Py_INIT_OK();
+    }
 
     tstate = PyThreadState_New(interp);
     if (tstate == NULL) {
         PyInterpreterState_Delete(interp);
-        return NULL;
+        *tstate_p = NULL;
+        return _Py_INIT_OK();
     }
 
     save_tstate = PyThreadState_Swap(tstate);
@@ -1343,8 +1305,9 @@ Py_NewInterpreter(void)
     /* XXX The following is lax in error checking */
 
     PyObject *modules = PyDict_New();
-    if (modules == NULL)
-        Py_FatalError("Py_NewInterpreter: can't make modules dictionary");
+    if (modules == NULL) {
+        return _Py_INIT_ERR("can't make modules dictionary");
+    }
     interp->modules = modules;
 
     sysmod = _PyImport_FindBuiltin("sys", modules);
@@ -1371,59 +1334,62 @@ Py_NewInterpreter(void)
 
     if (bimod != NULL && sysmod != NULL) {
         PyObject *pstderr;
+        _PyInitError err;
 
         /* Set up a preliminary stderr printer until we have enough
            infrastructure for the io module in place. */
         pstderr = PyFile_NewStdPrinter(fileno(stderr));
-        if (pstderr == NULL)
-            Py_FatalError("Py_NewInterpreter: can't set preliminary stderr");
+        if (pstderr == NULL) {
+            return _Py_INIT_ERR("can't set preliminary stderr");
+        }
         _PySys_SetObjectId(&PyId_stderr, pstderr);
         PySys_SetObject("__stderr__", pstderr);
         Py_DECREF(pstderr);
 
         err = _PyImportHooks_Init();
         if (_Py_INIT_FAILED(err)) {
-            goto init_failed;
+            return err;
         }
 
         err = initimport(interp, sysmod);
         if (_Py_INIT_FAILED(err)) {
-            goto init_failed;
+            return err;
         }
 
         err = initexternalimport(interp);
         if (_Py_INIT_FAILED(err)) {
-            goto init_failed;
+            return err;
         }
 
         err = initfsencoding(interp);
         if (_Py_INIT_FAILED(err)) {
-            goto init_failed;
+            return err;
         }
 
-        if (initstdio() < 0) {
-            err = _Py_INIT_ERR("can't initialize sys standard streams");
-            goto init_failed;
+        err = init_sys_streams();
+        if (_Py_INIT_FAILED(err)) {
+            return err;
         }
 
         err = add_main_module(interp);
         if (_Py_INIT_FAILED(err)) {
-            goto init_failed;
+            return err;
         }
 
         if (!Py_NoSiteFlag) {
             err = initsite();
             if (_Py_INIT_FAILED(err)) {
-                goto init_failed;
+                return err;
             }
         }
     }
 
-    if (!PyErr_Occurred())
-        return tstate;
+    if (PyErr_Occurred()) {
+        goto handle_error;
+    }
 
-init_failed:
-    _Py_FatalInitError(err);
+    *tstate_p = tstate;
+    return _Py_INIT_OK();
 
 handle_error:
     /* Oops, it didn't work.  Undo it all. */
@@ -1434,7 +1400,20 @@ handle_error:
     PyThreadState_Delete(tstate);
     PyInterpreterState_Delete(interp);
 
-    return NULL;
+    *tstate_p = NULL;
+    return _Py_INIT_OK();
+}
+
+PyThreadState *
+Py_NewInterpreter(void)
+{
+    PyThreadState *tstate;
+    _PyInitError err = new_interpreter(&tstate);
+    if (_Py_INIT_FAILED(err)) {
+        _Py_FatalInitError(err);
+    }
+    return tstate;
+
 }
 
 /* Delete an interpreter and its last thread.  This requires that the
@@ -1770,16 +1749,17 @@ error:
 }
 
 /* Initialize sys.stdin, stdout, stderr and builtins.open */
-static int
-initstdio(void)
+static _PyInitError
+init_sys_streams(void)
 {
     PyObject *iomod = NULL, *wrapper;
     PyObject *bimod = NULL;
     PyObject *m;
     PyObject *std = NULL;
-    int status = 0, fd;
+    int fd;
     PyObject * encoding_attr;
     char *pythonioencoding = NULL, *encoding, *errors;
+    _PyInitError res = _Py_INIT_OK();
 
     /* Hack to avoid a nasty recursion issue when Python is invoked
        in verbose mode: pre-import the Latin-1 and UTF-8 codecs */
@@ -1893,11 +1873,12 @@ initstdio(void)
     Py_DECREF(std);
 #endif
 
-    if (0) {
-  error:
-        status = -1;
-    }
+    goto done;
 
+error:
+    res = _Py_INIT_ERR("can't initialize sys standard streams");
+
+done:
     /* We won't need them anymore. */
     if (_Py_StandardStreamEncoding) {
         PyMem_RawFree(_Py_StandardStreamEncoding);
@@ -1910,7 +1891,7 @@ initstdio(void)
     PyMem_Free(pythonioencoding);
     Py_XDECREF(bimod);
     Py_XDECREF(iomod);
-    return status;
+    return res;
 }
 
 
diff --git a/Python/pystate.c b/Python/pystate.c
index 30f214e93d6..4544de9986f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -76,7 +76,7 @@ _PyRuntimeState_Fini(_PyRuntimeState *runtime)
 
 static void _PyGILState_NoteThreadState(PyThreadState* tstate);
 
-void
+_PyInitError
 _PyInterpreterState_Enable(_PyRuntimeState *runtime)
 {
     runtime->interpreters.next_id = 0;
@@ -85,9 +85,11 @@ _PyInterpreterState_Enable(_PyRuntimeState *runtime)
        initialized here. */
     if (runtime->interpreters.mutex == NULL) {
         runtime->interpreters.mutex = PyThread_allocate_lock();
-        if (runtime->interpreters.mutex == NULL)
-            Py_FatalError("Can't initialize threads for interpreter");
+        if (runtime->interpreters.mutex == NULL) {
+            return _Py_INIT_ERR("Can't initialize threads for interpreter");
+        }
     }
+    return _Py_INIT_OK();
 }
 
 PyInterpreterState *