diff --git a/Include/internal/pystate.h b/Include/internal/pystate.h
index 6cee272..e041d37 100644
--- a/Include/internal/pystate.h
+++ b/Include/internal/pystate.h
@@ -52,17 +52,17 @@
     wchar_t *program_name;
     /* Set by Py_SetPythonHome() or PYTHONHOME environment variable */
     wchar_t *home;
-    /* isolated and no_site_import are used to set Py_IsolatedFlag and
+    /* isolated and site_import are used to set Py_IsolatedFlag and
        Py_NoSiteFlag flags on Windows in read_pth_file(). These fields
        are ignored when their value are equal to -1 (unset). */
     int isolated;
-    int no_site_import;
+    int site_import;
 } _PyPathConfig;
 
 #define _PyPathConfig_INIT \
     {.module_search_path = NULL, \
      .isolated = -1, \
-     .no_site_import = -1}
+     .site_import = -1}
 /* Note: _PyPathConfig_INIT sets other fields to 0/NULL */
 
 PyAPI_DATA(_PyPathConfig) _Py_path_config;
diff --git a/Include/pylifecycle.h b/Include/pylifecycle.h
index 2fbc4f9..3e43a98 100644
--- a/Include/pylifecycle.h
+++ b/Include/pylifecycle.h
@@ -54,20 +54,16 @@
 PyAPI_FUNC(_PyInitError) _Py_InitializeCore(const _PyCoreConfig *);
 PyAPI_FUNC(int) _Py_IsCoreInitialized(void);
 
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(
-    _PyCoreConfig *config,
-    int *isolated,
-    int *no_site_import);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(_PyCoreConfig *config);
 PyAPI_FUNC(void) _PyCoreConfig_Clear(_PyCoreConfig *);
 PyAPI_FUNC(int) _PyCoreConfig_Copy(
     _PyCoreConfig *config,
     const _PyCoreConfig *config2);
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPathConfig(
-    _PyCoreConfig *config,
-    int *isolated,
-    int *no_site_import);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPathConfig(_PyCoreConfig *config);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_SetPathConfig(
     const _PyCoreConfig *config);
+PyAPI_FUNC(void) _PyCoreConfig_SetGlobalConfig(const _PyCoreConfig *config);
+
 
 PyAPI_FUNC(_PyInitError) _PyMainInterpreterConfig_Read(
     _PyMainInterpreterConfig *config,
diff --git a/Include/pystate.h b/Include/pystate.h
index ac09dc3..609f9c6 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -28,7 +28,7 @@
 typedef struct {
     int install_signal_handlers;  /* Install signal handlers? -1 means unset */
 
-    int ignore_environment; /* -E, Py_IgnoreEnvironmentFlag */
+    int ignore_environment; /* -E, Py_IgnoreEnvironmentFlag, -1 means unset */
     int use_hash_seed;      /* PYTHONHASHSEED=x */
     unsigned long hash_seed;
     const char *allocator;  /* Memory allocator: _PyMem_SetupAllocators() */
@@ -75,18 +75,42 @@
     wchar_t *dll_path;      /* Windows DLL path */
 #endif
 
-    /* Private fields */
-    int _disable_importlib; /* Needed by freeze_importlib */
+    /* If greater than 0, enable isolated mode: sys.path contains
+       neither the script's directory nor the user's site-packages directory.
+
+       Set to 1 by the -I command line option. If set to -1 (default), inherit
+       Py_IsolatedFlag value. */
+    int isolated;
+
+    /* If equal to zero, disable the import of the module site and the
+       site-dependent manipulations of sys.path that it entails. Also disable
+       these manipulations if site is explicitly imported later (call
+       site.main() if you want them to be triggered).
+
+       Set to 0 by the -S command line option. If set to -1 (default), set to
+       the negative value of Py_NoSiteFlag. */
+    int site_import;
+
+    /* --- Private fields -------- */
+
+    /* Install importlib? If set to 0, importlib is not initialized at all.
+       Needed by freeze_importlib: see install_importlib argument of
+       _Py_InitializeEx_Private(). */
+    int _install_importlib;
 } _PyCoreConfig;
 
 #define _PyCoreConfig_INIT \
     (_PyCoreConfig){ \
         .install_signal_handlers = -1, \
+        .ignore_environment = -1, \
         .use_hash_seed = -1, \
         .coerce_c_locale = -1, \
         .utf8_mode = -1, \
         .argc = -1, \
-        .nmodule_search_path = -1}
+        .nmodule_search_path = -1, \
+        .isolated = -1, \
+        .site_import = -1, \
+        ._install_importlib = 1}
 /* Note: _PyCoreConfig_INIT sets other fields to 0/NULL */
 
 /* Placeholders while working on the new configuration API
diff --git a/Modules/main.c b/Modules/main.c
index 2b68185..c9fd300 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -167,9 +167,15 @@
 
 
 static const char*
-config_get_env_var(const char *name)
+config_get_env_var(const _PyCoreConfig *config, const char *name)
 {
-    const char *var = Py_GETENV(name);
+    assert(config->ignore_environment >= 0);
+
+    if (config->ignore_environment) {
+        return NULL;
+    }
+
+    const char *var = getenv(name);
     if (var && var[0] != '\0') {
         return var;
     }
@@ -180,9 +186,11 @@
 
 
 static int
-config_get_env_var_dup(wchar_t **dest, wchar_t *wname, char *name)
+config_get_env_var_dup(const _PyCoreConfig *config, wchar_t **dest, wchar_t *wname, char *name)
 {
-    if (Py_IgnoreEnvironmentFlag) {
+    assert(config->ignore_environment >= 0);
+
+    if (config->ignore_environment) {
         *dest = NULL;
         return 0;
     }
@@ -224,32 +232,6 @@
 
 
 static void
-pymain_run_startup(PyCompilerFlags *cf)
-{
-    const char *startup = config_get_env_var("PYTHONSTARTUP");
-    if (startup == NULL) {
-        return;
-    }
-
-    FILE *fp = _Py_fopen(startup, "r");
-    if (fp == NULL) {
-        int save_errno = errno;
-        PySys_WriteStderr("Could not open PYTHONSTARTUP\n");
-        errno = save_errno;
-
-        PyErr_SetFromErrnoWithFilename(PyExc_OSError,
-                        startup);
-        PyErr_Print();
-        PyErr_Clear();
-        return;
-    }
-
-    (void) PyRun_SimpleFileExFlags(fp, startup, 0, cf);
-    PyErr_Clear();
-    fclose(fp);
-}
-
-static void
 pymain_run_interactive_hook(void)
 {
     PyObject *sys, *hook, *result;
@@ -443,11 +425,9 @@
     int debug;                   /* Py_DebugFlag, -b, PYTHONDEBUG */
     int inspect;                 /* Py_InspectFlag, -i, PYTHONINSPECT */
     int interactive;             /* Py_InteractiveFlag, -i */
-    int isolated;                /* Py_IsolatedFlag, -I */
     int optimization_level;      /* Py_OptimizeFlag, -O, PYTHONOPTIMIZE */
     int dont_write_bytecode;     /* Py_DontWriteBytecodeFlag, -B, PYTHONDONTWRITEBYTECODE */
     int no_user_site_directory;  /* Py_NoUserSiteDirectory, -I, -s, PYTHONNOUSERSITE */
-    int no_site_import;          /* Py_NoSiteFlag, -S */
     int use_unbuffered_io;       /* Py_UnbufferedStdioFlag, -u, PYTHONUNBUFFERED */
     int verbosity;               /* Py_VerboseFlag, -v, PYTHONVERBOSE */
     int quiet_flag;              /* Py_QuietFlag, -q */
@@ -498,6 +478,34 @@
      || pymain->module != NULL)
 
 
+static void
+clear_wstrlist(int len, wchar_t **list)
+{
+    for (int i=0; i < len; i++) {
+        PyMem_RawFree(list[i]);
+    }
+    PyMem_RawFree(list);
+}
+
+
+static wchar_t**
+copy_wstrlist(int len, wchar_t **list)
+{
+    assert((len > 0 && list != NULL) || len == 0);
+    size_t size = len * sizeof(list[0]);
+    wchar_t **list_copy = PyMem_RawMalloc(size);
+    for (int i=0; i < len; i++) {
+        wchar_t* arg = _PyMem_RawWcsdup(list[i]);
+        if (arg == NULL) {
+            clear_wstrlist(i, list);
+            return NULL;
+        }
+        list_copy[i] = arg;
+    }
+    return list_copy;
+}
+
+
 static wchar_t*
 pymain_wstrdup(_PyMain *pymain, const wchar_t *str)
 {
@@ -510,16 +518,6 @@
 }
 
 
-static void
-clear_wstrlist(int len, wchar_t **list)
-{
-    for (int i=0; i < len; i++) {
-        PyMem_RawFree(list[i]);
-    }
-    PyMem_RawFree(list);
-}
-
-
 static int
 pymain_init_cmdline_argv(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
@@ -570,6 +568,209 @@
 
 
 static void
+_PyCoreConfig_GetGlobalConfig(_PyCoreConfig *config)
+{
+    if (config->ignore_environment == -1) {
+        config->ignore_environment = Py_IgnoreEnvironmentFlag;
+    }
+    if (config->utf8_mode == -1) {
+        config->utf8_mode = Py_UTF8Mode;
+    }
+    if (config->isolated == -1) {
+        config->isolated = Py_IsolatedFlag;
+    }
+    if (config->site_import == -1) {
+        config->site_import = !Py_NoSiteFlag;
+    }
+}
+
+
+/* Get Py_xxx global configuration variables */
+static void
+pymain_get_global_config(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
+{
+    _PyCoreConfig_GetGlobalConfig(&pymain->config);
+
+    cmdline->bytes_warning = Py_BytesWarningFlag;
+    cmdline->debug = Py_DebugFlag;
+    cmdline->inspect = Py_InspectFlag;
+    cmdline->interactive = Py_InteractiveFlag;
+    cmdline->optimization_level = Py_OptimizeFlag;
+    cmdline->dont_write_bytecode = Py_DontWriteBytecodeFlag;
+    cmdline->no_user_site_directory = Py_NoUserSiteDirectory;
+    cmdline->use_unbuffered_io = Py_UnbufferedStdioFlag;
+    cmdline->verbosity = Py_VerboseFlag;
+    cmdline->quiet_flag = Py_QuietFlag;
+#ifdef MS_WINDOWS
+    cmdline->legacy_windows_fs_encoding = Py_LegacyWindowsFSEncodingFlag;
+    cmdline->legacy_windows_stdio = Py_LegacyWindowsStdioFlag;
+#endif
+    cmdline->check_hash_pycs_mode = _Py_CheckHashBasedPycsMode ;
+}
+
+
+/* Set Py_xxx global configuration variables from 'config' configuration. */
+void
+_PyCoreConfig_SetGlobalConfig(const _PyCoreConfig *config)
+{
+    if (config->ignore_environment != -1) {
+        Py_IgnoreEnvironmentFlag = config->ignore_environment;
+    }
+    if (config->utf8_mode != -1) {
+        Py_UTF8Mode = config->utf8_mode;
+    }
+    if (config->isolated != -1) {
+        Py_IsolatedFlag = config->isolated;
+    }
+    if (config->site_import != -1) {
+        Py_NoSiteFlag = !config->site_import;
+    }
+
+    /* Random or non-zero hash seed */
+    Py_HashRandomizationFlag = (config->use_hash_seed == 0 ||
+                                config->hash_seed != 0);
+}
+
+
+/* Set Py_xxx global configuration variables */
+static void
+pymain_set_global_config(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
+{
+    _PyCoreConfig_SetGlobalConfig(&pymain->config);
+
+    Py_BytesWarningFlag = cmdline->bytes_warning;
+    Py_DebugFlag = cmdline->debug;
+    Py_InspectFlag = cmdline->inspect;
+    Py_InteractiveFlag = cmdline->interactive;
+    Py_OptimizeFlag = cmdline->optimization_level;
+    Py_DontWriteBytecodeFlag = cmdline->dont_write_bytecode;
+    Py_NoUserSiteDirectory = cmdline->no_user_site_directory;
+    Py_UnbufferedStdioFlag = cmdline->use_unbuffered_io;
+    Py_VerboseFlag = cmdline->verbosity;
+    Py_QuietFlag = cmdline->quiet_flag;
+    _Py_CheckHashBasedPycsMode = cmdline->check_hash_pycs_mode;
+#ifdef MS_WINDOWS
+    Py_LegacyWindowsFSEncodingFlag = cmdline->legacy_windows_fs_encoding;
+    Py_LegacyWindowsStdioFlag = cmdline->legacy_windows_stdio;
+#endif
+}
+
+
+/* Free memory allocated in config, but don't clear all attributes */
+void
+_PyCoreConfig_Clear(_PyCoreConfig *config)
+{
+#define CLEAR(ATTR) \
+    do { \
+        PyMem_RawFree(ATTR); \
+        ATTR = NULL; \
+    } while (0)
+#define CLEAR_WSTRLIST(LEN, LIST) \
+    do { \
+        clear_wstrlist(LEN, LIST); \
+        LEN = 0; \
+        LIST = NULL; \
+    } while (0)
+
+    CLEAR(config->pycache_prefix);
+    CLEAR(config->module_search_path_env);
+    CLEAR(config->home);
+    CLEAR(config->program_name);
+    CLEAR(config->program);
+
+    CLEAR_WSTRLIST(config->argc, config->argv);
+    config->argc = -1;
+
+    CLEAR_WSTRLIST(config->nwarnoption, config->warnoptions);
+    CLEAR_WSTRLIST(config->nxoption, config->xoptions);
+    CLEAR_WSTRLIST(config->nmodule_search_path, config->module_search_paths);
+    config->nmodule_search_path = -1;
+
+    CLEAR(config->executable);
+    CLEAR(config->prefix);
+    CLEAR(config->base_prefix);
+    CLEAR(config->exec_prefix);
+#ifdef MS_WINDOWS
+    CLEAR(config->dll_path);
+#endif
+    CLEAR(config->base_exec_prefix);
+#undef CLEAR
+#undef CLEAR_WSTRLIST
+}
+
+
+int
+_PyCoreConfig_Copy(_PyCoreConfig *config, const _PyCoreConfig *config2)
+{
+    _PyCoreConfig_Clear(config);
+
+#define COPY_ATTR(ATTR) config->ATTR = config2->ATTR
+#define COPY_STR_ATTR(ATTR) \
+    do { \
+        if (config2->ATTR != NULL) { \
+            config->ATTR = _PyMem_RawWcsdup(config2->ATTR); \
+            if (config->ATTR == NULL) { \
+                return -1; \
+            } \
+        } \
+    } while (0)
+#define COPY_WSTRLIST(LEN, LIST) \
+    do { \
+        if (config2->LIST != NULL) { \
+            config->LIST = copy_wstrlist(config2->LEN, config2->LIST); \
+            if (config->LIST == NULL) { \
+                return -1; \
+            } \
+        } \
+        config->LEN = config2->LEN; \
+    } while (0)
+
+    COPY_ATTR(ignore_environment);
+    COPY_ATTR(use_hash_seed);
+    COPY_ATTR(hash_seed);
+    COPY_ATTR(_install_importlib);
+    COPY_ATTR(allocator);
+    COPY_ATTR(dev_mode);
+    COPY_ATTR(faulthandler);
+    COPY_ATTR(tracemalloc);
+    COPY_ATTR(import_time);
+    COPY_ATTR(show_ref_count);
+    COPY_ATTR(show_alloc_count);
+    COPY_ATTR(dump_refs);
+    COPY_ATTR(malloc_stats);
+    COPY_ATTR(utf8_mode);
+
+    COPY_STR_ATTR(pycache_prefix);
+    COPY_STR_ATTR(module_search_path_env);
+    COPY_STR_ATTR(home);
+    COPY_STR_ATTR(program_name);
+    COPY_STR_ATTR(program);
+
+    COPY_WSTRLIST(argc, argv);
+    COPY_WSTRLIST(nwarnoption, warnoptions);
+    COPY_WSTRLIST(nxoption, xoptions);
+    COPY_WSTRLIST(nmodule_search_path, module_search_paths);
+
+    COPY_STR_ATTR(executable);
+    COPY_STR_ATTR(prefix);
+    COPY_STR_ATTR(base_prefix);
+    COPY_STR_ATTR(exec_prefix);
+#ifdef MS_WINDOWS
+    COPY_STR_ATTR(dll_path);
+#endif
+    COPY_STR_ATTR(base_exec_prefix);
+
+    COPY_ATTR(isolated);
+    COPY_ATTR(site_import);
+
+#undef COPY_ATTR
+#undef COPY_STR_ATTR
+#undef COPY_WSTRLIST
+    return 0;
+}
+
+
+static void
 pymain_clear_cmdline(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
     PyMemAllocatorEx old_alloc;
@@ -816,7 +1017,7 @@
 
         case 'I':
             config->ignore_environment++;
-            cmdline->isolated++;
+            config->isolated++;
             cmdline->no_user_site_directory++;
             break;
 
@@ -835,7 +1036,7 @@
             break;
 
         case 'S':
-            cmdline->no_site_import++;
+            config->site_import = 0;
             break;
 
         case 'E':
@@ -1059,14 +1260,15 @@
    Return 0 on success.
    Set pymain->err and return -1 on error. */
 static _PyInitError
-cmdline_init_env_warnoptions(_Py_CommandLineDetails *cmdline)
+cmdline_init_env_warnoptions(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
-    if (Py_IgnoreEnvironmentFlag) {
+    if (pymain->config.ignore_environment) {
         return _Py_INIT_OK();
     }
 
     wchar_t *env;
-    int res = config_get_env_var_dup(&env, L"PYTHONWARNINGS", "PYTHONWARNINGS");
+    int res = config_get_env_var_dup(&pymain->config, &env,
+                                     L"PYTHONWARNINGS", "PYTHONWARNINGS");
     if (res < 0) {
         return DECODE_LOCALE_ERR("PYTHONWARNINGS", res);
     }
@@ -1161,7 +1363,7 @@
        so the actual executable path is passed in an environment variable.
        See Lib/plat-mac/bundlebuiler.py for details about the bootstrap
        script. */
-    const char *p = config_get_env_var("PYTHONEXECUTABLE");
+    const char *p = config_get_env_var(config, "PYTHONEXECUTABLE");
     if (p != NULL) {
         size_t len;
         wchar_t* program_name = Py_DecodeLocale(p, &len);
@@ -1233,24 +1435,6 @@
 }
 
 
-static wchar_t**
-copy_wstrlist(int len, wchar_t **list)
-{
-    assert((len > 0 && list != NULL) || len == 0);
-    size_t size = len * sizeof(list[0]);
-    wchar_t **list_copy = PyMem_RawMalloc(size);
-    for (int i=0; i < len; i++) {
-        wchar_t* arg = _PyMem_RawWcsdup(list[i]);
-        if (arg == NULL) {
-            clear_wstrlist(i, list);
-            return NULL;
-        }
-        list_copy[i] = arg;
-    }
-    return list_copy;
-}
-
-
 static int
 pymain_init_core_argv(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
@@ -1367,64 +1551,6 @@
 }
 
 
-/* Get Py_xxx global configuration variables */
-static void
-pymain_get_global_config(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
-{
-    cmdline->bytes_warning = Py_BytesWarningFlag;
-    cmdline->debug = Py_DebugFlag;
-    cmdline->inspect = Py_InspectFlag;
-    cmdline->interactive = Py_InteractiveFlag;
-    cmdline->isolated = Py_IsolatedFlag;
-    cmdline->optimization_level = Py_OptimizeFlag;
-    cmdline->dont_write_bytecode = Py_DontWriteBytecodeFlag;
-    cmdline->no_user_site_directory = Py_NoUserSiteDirectory;
-    cmdline->no_site_import = Py_NoSiteFlag;
-    cmdline->use_unbuffered_io = Py_UnbufferedStdioFlag;
-    cmdline->verbosity = Py_VerboseFlag;
-    cmdline->quiet_flag = Py_QuietFlag;
-#ifdef MS_WINDOWS
-    cmdline->legacy_windows_fs_encoding = Py_LegacyWindowsFSEncodingFlag;
-    cmdline->legacy_windows_stdio = Py_LegacyWindowsStdioFlag;
-#endif
-    cmdline->check_hash_pycs_mode = _Py_CheckHashBasedPycsMode ;
-
-    pymain->config.ignore_environment = Py_IgnoreEnvironmentFlag;
-    pymain->config.utf8_mode = Py_UTF8Mode;
-}
-
-
-/* Set Py_xxx global configuration variables */
-static void
-pymain_set_global_config(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
-{
-    Py_BytesWarningFlag = cmdline->bytes_warning;
-    Py_DebugFlag = cmdline->debug;
-    Py_InspectFlag = cmdline->inspect;
-    Py_InteractiveFlag = cmdline->interactive;
-    Py_IsolatedFlag = cmdline->isolated;
-    Py_OptimizeFlag = cmdline->optimization_level;
-    Py_DontWriteBytecodeFlag = cmdline->dont_write_bytecode;
-    Py_NoUserSiteDirectory = cmdline->no_user_site_directory;
-    Py_NoSiteFlag = cmdline->no_site_import;
-    Py_UnbufferedStdioFlag = cmdline->use_unbuffered_io;
-    Py_VerboseFlag = cmdline->verbosity;
-    Py_QuietFlag = cmdline->quiet_flag;
-    _Py_CheckHashBasedPycsMode = cmdline->check_hash_pycs_mode;
-#ifdef MS_WINDOWS
-    Py_LegacyWindowsFSEncodingFlag = cmdline->legacy_windows_fs_encoding;
-    Py_LegacyWindowsStdioFlag = cmdline->legacy_windows_stdio;
-#endif
-
-    Py_IgnoreEnvironmentFlag = pymain->config.ignore_environment;
-    Py_UTF8Mode = pymain->config.utf8_mode;
-
-    /* Random or non-zero hash seed */
-    Py_HashRandomizationFlag = (pymain->config.use_hash_seed == 0 ||
-                                pymain->config.hash_seed != 0);
-}
-
-
 static void
 pymain_import_readline(_PyMain *pymain)
 {
@@ -1498,11 +1624,38 @@
 
 
 static void
+pymain_run_startup(_PyMain *pymain, PyCompilerFlags *cf)
+{
+    const char *startup = config_get_env_var(&pymain->config, "PYTHONSTARTUP");
+    if (startup == NULL) {
+        return;
+    }
+
+    FILE *fp = _Py_fopen(startup, "r");
+    if (fp == NULL) {
+        int save_errno = errno;
+        PySys_WriteStderr("Could not open PYTHONSTARTUP\n");
+        errno = save_errno;
+
+        PyErr_SetFromErrnoWithFilename(PyExc_OSError,
+                        startup);
+        PyErr_Print();
+        PyErr_Clear();
+        return;
+    }
+
+    (void) PyRun_SimpleFileExFlags(fp, startup, 0, cf);
+    PyErr_Clear();
+    fclose(fp);
+}
+
+
+static void
 pymain_run_filename(_PyMain *pymain, PyCompilerFlags *cf)
 {
     if (pymain->filename == NULL && pymain->stdin_is_interactive) {
         Py_InspectFlag = 0; /* do exit on SystemExit */
-        pymain_run_startup(cf);
+        pymain_run_startup(pymain, cf);
         pymain_run_interactive_hook();
     }
 
@@ -1531,7 +1684,7 @@
 {
     /* Check this environment variable at the end, to give programs the
        opportunity to set it from Python. */
-    if (!Py_InspectFlag && config_get_env_var("PYTHONINSPECT")) {
+    if (!Py_InspectFlag && config_get_env_var(&pymain->config, "PYTHONINSPECT")) {
         Py_InspectFlag = 1;
     }
 
@@ -1640,7 +1793,7 @@
     int nframe;
     int valid;
 
-    const char *env = config_get_env_var("PYTHONTRACEMALLOC");
+    const char *env = config_get_env_var(config, "PYTHONTRACEMALLOC");
     if (env) {
         if (!pymain_str_to_int(env, &nframe)) {
             valid = (nframe >= 1);
@@ -1685,8 +1838,8 @@
 {
     wchar_t *env;
 
-    int res = config_get_env_var_dup(
-        &env, L"PYTHONPYCACHEPREFIX", "PYTHONPYCACHEPREFIX");
+    int res = config_get_env_var_dup(config, &env,
+                                     L"PYTHONPYCACHEPREFIX", "PYTHONPYCACHEPREFIX");
     if (res < 0) {
         return DECODE_LOCALE_ERR("PYTHONPYCACHEPREFIX", res);
     } else if (env) {
@@ -1712,9 +1865,9 @@
 
 
 static void
-get_env_flag(int *flag, const char *name)
+get_env_flag(_PyCoreConfig *config, int *flag, const char *name)
 {
-    const char *var = config_get_env_var(name);
+    const char *var = config_get_env_var(config, name);
     if (!var) {
         return;
     }
@@ -1730,19 +1883,20 @@
 
 
 static void
-cmdline_get_env_flags(_Py_CommandLineDetails *cmdline)
+cmdline_get_env_flags(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
-    get_env_flag(&cmdline->debug, "PYTHONDEBUG");
-    get_env_flag(&cmdline->verbosity, "PYTHONVERBOSE");
-    get_env_flag(&cmdline->optimization_level, "PYTHONOPTIMIZE");
-    get_env_flag(&cmdline->inspect, "PYTHONINSPECT");
-    get_env_flag(&cmdline->dont_write_bytecode, "PYTHONDONTWRITEBYTECODE");
-    get_env_flag(&cmdline->no_user_site_directory, "PYTHONNOUSERSITE");
-    get_env_flag(&cmdline->use_unbuffered_io, "PYTHONUNBUFFERED");
+    _PyCoreConfig *config = &pymain->config;
+    get_env_flag(config, &cmdline->debug, "PYTHONDEBUG");
+    get_env_flag(config, &cmdline->verbosity, "PYTHONVERBOSE");
+    get_env_flag(config, &cmdline->optimization_level, "PYTHONOPTIMIZE");
+    get_env_flag(config, &cmdline->inspect, "PYTHONINSPECT");
+    get_env_flag(config, &cmdline->dont_write_bytecode, "PYTHONDONTWRITEBYTECODE");
+    get_env_flag(config, &cmdline->no_user_site_directory, "PYTHONNOUSERSITE");
+    get_env_flag(config, &cmdline->use_unbuffered_io, "PYTHONUNBUFFERED");
 #ifdef MS_WINDOWS
-    get_env_flag(&cmdline->legacy_windows_fs_encoding,
+    get_env_flag(config, &cmdline->legacy_windows_fs_encoding,
                  "PYTHONLEGACYWINDOWSFSENCODING");
-    get_env_flag(&cmdline->legacy_windows_stdio,
+    get_env_flag(config, &cmdline->legacy_windows_stdio,
                  "PYTHONLEGACYWINDOWSSTDIO");
 #endif
 }
@@ -1763,7 +1917,7 @@
         return _Py_INIT_OK();
     }
 
-    int res = config_get_env_var_dup(&home, L"PYTHONHOME", "PYTHONHOME");
+    int res = config_get_env_var_dup(config, &home, L"PYTHONHOME", "PYTHONHOME");
     if (res < 0) {
         return DECODE_LOCALE_ERR("PYTHONHOME", res);
     }
@@ -1776,7 +1930,7 @@
 config_init_hash_seed(_PyCoreConfig *config)
 {
     if (config->use_hash_seed < 0) {
-        const char *seed_text = config_get_env_var("PYTHONHASHSEED");
+        const char *seed_text = config_get_env_var(config, "PYTHONHASHSEED");
         int use_hash_seed;
         unsigned long hash_seed;
         if (_Py_ReadHashSeed(seed_text, &use_hash_seed, &hash_seed) < 0) {
@@ -1793,8 +1947,8 @@
 static _PyInitError
 config_init_utf8_mode(_PyCoreConfig *config)
 {
-    /* The option was already set by Py_UTF8Mode,
-       Py_LegacyWindowsFSEncodingFlag or PYTHONLEGACYWINDOWSFSENCODING. */
+    /* The option was already set in config.Py_UTF8Mode,
+       by Py_LegacyWindowsFSEncodingFlag or PYTHONLEGACYWINDOWSFSENCODING. */
     if (config->utf8_mode >= 0) {
         return _Py_INIT_OK();
     }
@@ -1820,7 +1974,7 @@
         return _Py_INIT_OK();
     }
 
-    const char *opt = config_get_env_var("PYTHONUTF8");
+    const char *opt = config_get_env_var(config, "PYTHONUTF8");
     if (opt) {
         if (strcmp(opt, "1") == 0) {
             config->utf8_mode = 1;
@@ -1842,16 +1996,16 @@
 static _PyInitError
 config_read_env_vars(_PyCoreConfig *config)
 {
-    config->allocator = config_get_env_var("PYTHONMALLOC");
+    config->allocator = config_get_env_var(config, "PYTHONMALLOC");
 
-    if (config_get_env_var("PYTHONDUMPREFS")) {
+    if (config_get_env_var(config, "PYTHONDUMPREFS")) {
         config->dump_refs = 1;
     }
-    if (config_get_env_var("PYTHONMALLOCSTATS")) {
+    if (config_get_env_var(config, "PYTHONMALLOCSTATS")) {
         config->malloc_stats = 1;
     }
 
-    const char *env = config_get_env_var("PYTHONCOERCECLOCALE");
+    const char *env = config_get_env_var(config, "PYTHONCOERCECLOCALE");
     if (env) {
         if (strcmp(env, "0") == 0) {
             config->coerce_c_locale = 0;
@@ -1865,7 +2019,7 @@
     }
 
     wchar_t *path;
-    int res = config_get_env_var_dup(&path, L"PYTHONPATH", "PYTHONPATH");
+    int res = config_get_env_var_dup(config, &path, L"PYTHONPATH", "PYTHONPATH");
     if (res < 0) {
         return DECODE_LOCALE_ERR("PYTHONPATH", res);
     }
@@ -1884,16 +2038,16 @@
 config_read_complex_options(_PyCoreConfig *config)
 {
     /* More complex options configured by env var and -X option */
-    if (config_get_env_var("PYTHONFAULTHANDLER")
+    if (config_get_env_var(config, "PYTHONFAULTHANDLER")
        || config_get_xoption(config, L"faulthandler")) {
         config->faulthandler = 1;
     }
-    if (config_get_env_var("PYTHONPROFILEIMPORTTIME")
+    if (config_get_env_var(config, "PYTHONPROFILEIMPORTTIME")
        || config_get_xoption(config, L"importtime")) {
         config->import_time = 1;
     }
     if (config_get_xoption(config, L"dev" ) ||
-        config_get_env_var("PYTHONDEVMODE"))
+        config_get_env_var(config, "PYTHONDEVMODE"))
     {
         config->dev_mode = 1;
         config->faulthandler = 1;
@@ -1930,14 +2084,10 @@
         return res;
     }
 
-    /* Set Py_IgnoreEnvironmentFlag for Py_GETENV() */
-    _PyCoreConfig *config = &pymain->config;
-    Py_IgnoreEnvironmentFlag = config->ignore_environment;
-
     /* Get environment variables */
-    cmdline_get_env_flags(cmdline);
+    cmdline_get_env_flags(pymain, cmdline);
 
-    err = cmdline_init_env_warnoptions(cmdline);
+    err = cmdline_init_env_warnoptions(pymain, cmdline);
     if (_Py_INIT_FAILED(err)) {
         pymain->err = err;
         return -1;
@@ -1945,7 +2095,7 @@
 
 #ifdef MS_WINDOWS
     if (cmdline->legacy_windows_fs_encoding) {
-        config->utf8_mode = 0;
+        pymain->config.utf8_mode = 0;
     }
 #endif
 
@@ -1953,9 +2103,7 @@
         return -1;
     }
 
-    err = _PyCoreConfig_Read(config,
-                             &cmdline->isolated,
-                             &cmdline->no_site_import);
+    err = _PyCoreConfig_Read(&pymain->config);
 
     if (_Py_INIT_FAILED(err)) {
         pymain->err = err;
@@ -1970,9 +2118,12 @@
 static int
 pymain_read_conf(_PyMain *pymain, _Py_CommandLineDetails *cmdline)
 {
+    _PyCoreConfig *config = &pymain->config;
+    _PyCoreConfig save_config = _PyCoreConfig_INIT;
+    char *oldloc = NULL;
     int res = -1;
 
-    char *oldloc = _PyMem_RawStrdup(setlocale(LC_ALL, NULL));
+    oldloc = _PyMem_RawStrdup(setlocale(LC_ALL, NULL));
     if (oldloc == NULL) {
         pymain->err = _Py_INIT_NO_MEMORY();
         goto done;
@@ -1983,10 +2134,14 @@
 
     int locale_coerced = 0;
     int loops = 0;
-    int init_ignore_env = pymain->config.ignore_environment;
+
+    if (_PyCoreConfig_Copy(&save_config, config) < 0) {
+        pymain->err = _Py_INIT_NO_MEMORY();
+        goto done;
+    }
 
     while (1) {
-        int utf8_mode = pymain->config.utf8_mode;
+        int utf8_mode = config->utf8_mode;
         int encoding_changed = 0;
 
         /* Watchdog to prevent an infinite loop */
@@ -2017,20 +2172,20 @@
          * See the documentation of the PYTHONCOERCECLOCALE setting for more
          * details.
          */
-        if (pymain->config.coerce_c_locale == 1 && !locale_coerced) {
+        if (config->coerce_c_locale == 1 && !locale_coerced) {
             locale_coerced = 1;
-            _Py_CoerceLegacyLocale(&pymain->config);
+            _Py_CoerceLegacyLocale(config);
             encoding_changed = 1;
         }
 
         if (utf8_mode == -1) {
-            if (pymain->config.utf8_mode == 1) {
+            if (config->utf8_mode == 1) {
                 /* UTF-8 Mode enabled */
                 encoding_changed = 1;
             }
         }
         else {
-            if (pymain->config.utf8_mode != utf8_mode) {
+            if (config->utf8_mode != utf8_mode) {
                 encoding_changed = 1;
             }
         }
@@ -2039,16 +2194,17 @@
             break;
         }
 
-        /* Reset the configuration, except UTF-8 Mode. Set Py_UTF8Mode for
-           Py_DecodeLocale(). Reset Py_IgnoreEnvironmentFlag, modified by
-           pymain_read_conf_impl(). Reset Py_IsolatedFlag and Py_NoSiteFlag
-           modified by _PyCoreConfig_Read(). */
-        Py_UTF8Mode = pymain->config.utf8_mode;
-        Py_IgnoreEnvironmentFlag = init_ignore_env;
-        _PyCoreConfig_Clear(&pymain->config);
+        /* Reset the configuration before reading the configuration,
+           except UTF-8 Mode. */
+        int new_utf8_mode = config->utf8_mode;
+        if (_PyCoreConfig_Copy(config, &save_config) < 0) {
+            pymain->err = _Py_INIT_NO_MEMORY();
+            goto done;
+        }
         pymain_clear_cmdline(pymain, cmdline);
         memset(cmdline, 0, sizeof(*cmdline));
         pymain_get_global_config(pymain, cmdline);
+        pymain->config.utf8_mode = new_utf8_mode;
 
         /* The encoding changed: read again the configuration
            with the new encoding */
@@ -2056,6 +2212,7 @@
     res = 0;
 
 done:
+    _PyCoreConfig_Clear(&save_config);
     if (oldloc != NULL) {
         setlocale(LC_ALL, oldloc);
         PyMem_RawFree(oldloc);
@@ -2106,10 +2263,12 @@
  */
 
 _PyInitError
-_PyCoreConfig_Read(_PyCoreConfig *config, int *isolated, int *no_site_import)
+_PyCoreConfig_Read(_PyCoreConfig *config)
 {
     _PyInitError err;
 
+    _PyCoreConfig_GetGlobalConfig(config);
+
     err = config_read_env_vars(config);
     if (_Py_INIT_FAILED(err)) {
         return err;
@@ -2150,8 +2309,8 @@
         config->install_signal_handlers = 1;
     }
 
-    if (!config->_disable_importlib) {
-        err = _PyCoreConfig_InitPathConfig(config, isolated, no_site_import);
+    if (config->_install_importlib) {
+        err = _PyCoreConfig_InitPathConfig(config);
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
@@ -2161,116 +2320,6 @@
 
 
 void
-_PyCoreConfig_Clear(_PyCoreConfig *config)
-{
-#define CLEAR(ATTR) \
-    do { \
-        PyMem_RawFree(ATTR); \
-        ATTR = NULL; \
-    } while (0)
-#define CLEAR_WSTRLIST(LEN, LIST) \
-    do { \
-        clear_wstrlist(LEN, LIST); \
-        LEN = 0; \
-        LIST = NULL; \
-    } while (0)
-
-    CLEAR(config->pycache_prefix);
-    CLEAR(config->module_search_path_env);
-    CLEAR(config->home);
-    CLEAR(config->program_name);
-    CLEAR(config->program);
-
-    CLEAR_WSTRLIST(config->argc, config->argv);
-    config->argc = -1;
-
-    CLEAR_WSTRLIST(config->nwarnoption, config->warnoptions);
-    CLEAR_WSTRLIST(config->nxoption, config->xoptions);
-    CLEAR_WSTRLIST(config->nmodule_search_path, config->module_search_paths);
-    config->nmodule_search_path = -1;
-
-    CLEAR(config->executable);
-    CLEAR(config->prefix);
-    CLEAR(config->base_prefix);
-    CLEAR(config->exec_prefix);
-#ifdef MS_WINDOWS
-    CLEAR(config->dll_path);
-#endif
-    CLEAR(config->base_exec_prefix);
-#undef CLEAR
-#undef CLEAR_WSTRLIST
-}
-
-
-int
-_PyCoreConfig_Copy(_PyCoreConfig *config, const _PyCoreConfig *config2)
-{
-    _PyCoreConfig_Clear(config);
-
-#define COPY_ATTR(ATTR) config->ATTR = config2->ATTR
-#define COPY_STR_ATTR(ATTR) \
-    do { \
-        if (config2->ATTR != NULL) { \
-            config->ATTR = _PyMem_RawWcsdup(config2->ATTR); \
-            if (config->ATTR == NULL) { \
-                return -1; \
-            } \
-        } \
-    } while (0)
-#define COPY_WSTRLIST(LEN, LIST) \
-    do { \
-        if (config2->LIST != NULL) { \
-            config->LIST = copy_wstrlist(config2->LEN, config2->LIST); \
-            if (config->LIST == NULL) { \
-                return -1; \
-            } \
-        } \
-        config->LEN = config2->LEN; \
-    } while (0)
-
-    COPY_ATTR(ignore_environment);
-    COPY_ATTR(use_hash_seed);
-    COPY_ATTR(hash_seed);
-    COPY_ATTR(_disable_importlib);
-    COPY_ATTR(allocator);
-    COPY_ATTR(dev_mode);
-    COPY_ATTR(faulthandler);
-    COPY_ATTR(tracemalloc);
-    COPY_ATTR(import_time);
-    COPY_ATTR(show_ref_count);
-    COPY_ATTR(show_alloc_count);
-    COPY_ATTR(dump_refs);
-    COPY_ATTR(malloc_stats);
-    COPY_ATTR(utf8_mode);
-
-    COPY_STR_ATTR(pycache_prefix);
-    COPY_STR_ATTR(module_search_path_env);
-    COPY_STR_ATTR(home);
-    COPY_STR_ATTR(program_name);
-    COPY_STR_ATTR(program);
-
-    COPY_WSTRLIST(argc, argv);
-    COPY_WSTRLIST(nwarnoption, warnoptions);
-    COPY_WSTRLIST(nxoption, xoptions);
-    COPY_WSTRLIST(nmodule_search_path, module_search_paths);
-
-    COPY_STR_ATTR(executable);
-    COPY_STR_ATTR(prefix);
-    COPY_STR_ATTR(base_prefix);
-    COPY_STR_ATTR(exec_prefix);
-#ifdef MS_WINDOWS
-    COPY_STR_ATTR(dll_path);
-#endif
-    COPY_STR_ATTR(base_exec_prefix);
-
-#undef COPY_ATTR
-#undef COPY_STR_ATTR
-#undef COPY_WSTRLIST
-    return 0;
-}
-
-
-void
 _PyMainInterpreterConfig_Clear(_PyMainInterpreterConfig *config)
 {
     Py_CLEAR(config->argv);
@@ -2384,7 +2433,7 @@
                       config->argc, config->argv);
     }
 
-    if (!config->_disable_importlib) {
+    if (config->_install_importlib) {
         COPY_WSTR(executable);
         COPY_WSTR(prefix);
         COPY_WSTR(base_prefix);
@@ -2491,7 +2540,6 @@
     fedisableexcept(FE_OVERFLOW);
 #endif
 
-    pymain->config._disable_importlib = 0;
     pymain->config.install_signal_handlers = 1;
 }
 
diff --git a/PC/getpathp.c b/PC/getpathp.c
index df4cb0a..e57893d 100644
--- a/PC/getpathp.c
+++ b/PC/getpathp.c
@@ -563,7 +563,7 @@
     wcscpy_s(prefix, MAXPATHLEN+1, path);
     reduce(prefix);
     config->isolated = 1;
-    config->no_site_import = 1;
+    config->site_import = 0;
 
     size_t bufsiz = MAXPATHLEN;
     size_t prefixlen = wcslen(prefix);
@@ -588,7 +588,7 @@
         }
 
         if (strcmp(line, "import site") == 0) {
-            config->no_site_import = 0;
+            config->site_import = 1;
             continue;
         }
         else if (strncmp(line, "import ", 7) == 0) {
diff --git a/Python/pathconfig.c b/Python/pathconfig.c
index 1f6177f..509ea8e 100644
--- a/Python/pathconfig.c
+++ b/Python/pathconfig.c
@@ -283,8 +283,7 @@
 
 
 _PyInitError
-_PyCoreConfig_InitPathConfig(_PyCoreConfig *config,
-                             int *isolated, int *no_site_import)
+_PyCoreConfig_InitPathConfig(_PyCoreConfig *config)
 {
     _PyPathConfig path_config = _PyPathConfig_INIT;
     _PyInitError err;
@@ -345,11 +344,11 @@
         }
     }
 
-    if (path_config.isolated != -1 && isolated != NULL) {
-        *isolated = path_config.isolated;
+    if (path_config.isolated != -1) {
+        config->isolated = path_config.isolated;
     }
-    if (path_config.no_site_import != -1 && no_site_import != NULL) {
-        *no_site_import = path_config.no_site_import;
+    if (path_config.site_import != -1) {
+        config->site_import = path_config.site_import;
     }
 
     _PyPathConfig_Clear(&path_config);
@@ -375,10 +374,7 @@
     _PyInitError err;
     _PyCoreConfig config = _PyCoreConfig_INIT;
 
-    /* Py_IsolatedFlag and Py_NoSiteFlag are left unchanged: pass NULL.
-       _PyCoreConfig_InitPathConfig() will be called later and will set
-       these flags. */
-    err = _PyCoreConfig_Read(&config, NULL, NULL);
+    err = _PyCoreConfig_Read(&config);
     if (_Py_INIT_FAILED(err)) {
         goto error;
     }
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 584aa55..c88e945 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -599,12 +599,9 @@
 {
     assert(core_config != NULL);
 
-    PyInterpreterState *interp;
-    PyThreadState *tstate;
-    PyObject *bimod, *sysmod, *pstderr;
-    _PyInitError err;
+    _PyCoreConfig_SetGlobalConfig(core_config);
 
-    err = _PyRuntime_Initialize();
+    _PyInitError err = _PyRuntime_Initialize();
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
@@ -646,17 +643,12 @@
         return err;
     }
 
-    if (!core_config->use_hash_seed || core_config->hash_seed) {
-        /* Random or non-zero hash seed */
-        Py_HashRandomizationFlag = 1;
-    }
-
     err = _PyInterpreterState_Enable(&_PyRuntime);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
 
-    interp = PyInterpreterState_New();
+    PyInterpreterState *interp = PyInterpreterState_New();
     if (interp == NULL) {
         return _Py_INIT_ERR("can't make main interpreter");
     }
@@ -664,8 +656,9 @@
     if (_PyCoreConfig_Copy(&interp->core_config, core_config) < 0) {
         return _Py_INIT_ERR("failed to copy core config");
     }
+    core_config = &interp->core_config;
 
-    tstate = PyThreadState_New(interp);
+    PyThreadState *tstate = PyThreadState_New(interp);
     if (tstate == NULL)
         return _Py_INIT_ERR("can't make first thread");
     (void) PyThreadState_Swap(tstate);
@@ -699,6 +692,7 @@
         return _Py_INIT_ERR("can't make modules dictionary");
     interp->modules = modules;
 
+    PyObject *sysmod;
     err = _PySys_BeginInit(&sysmod);
     if (_Py_INIT_FAILED(err)) {
         return err;
@@ -720,7 +714,7 @@
     if (_PyStructSequence_Init() < 0)
         return _Py_INIT_ERR("can't initialize structseq");
 
-    bimod = _PyBuiltin_Init();
+    PyObject *bimod = _PyBuiltin_Init();
     if (bimod == NULL)
         return _Py_INIT_ERR("can't initialize builtins modules");
     _PyImport_FixupBuiltin(bimod, "builtins", modules);
@@ -734,7 +728,7 @@
 
     /* Set up a preliminary stderr printer until we have enough
        infrastructure for the io module in place. */
-    pstderr = PyFile_NewStdPrinter(fileno(stderr));
+    PyObject *pstderr = PyFile_NewStdPrinter(fileno(stderr));
     if (pstderr == NULL)
         return _Py_INIT_ERR("can't set preliminary stderr");
     _PySys_SetObjectId(&PyId_stderr, pstderr);
@@ -759,7 +753,7 @@
     if (!_PyContext_Init())
         return _Py_INIT_ERR("can't init context");
 
-    if (!core_config->_disable_importlib) {
+    if (core_config->_install_importlib) {
         err = _PyCoreConfig_SetPathConfig(core_config);
         if (_Py_INIT_FAILED(err)) {
             return err;
@@ -767,7 +761,7 @@
     }
 
     /* This call sets up builtin and frozen import support */
-    if (!interp->core_config._disable_importlib) {
+    if (core_config->_install_importlib) {
         err = initimport(interp, sysmod);
         if (_Py_INIT_FAILED(err)) {
             return err;
@@ -809,21 +803,20 @@
 _PyInitError
 _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
 {
-    PyInterpreterState *interp;
-    PyThreadState *tstate;
-    _PyInitError err;
-
     if (!_PyRuntime.core_initialized) {
         return _Py_INIT_ERR("runtime core not initialized");
     }
 
     /* Get current thread state and interpreter pointer */
-    tstate = PyThreadState_GET();
-    if (!tstate)
+    PyThreadState *tstate = PyThreadState_GET();
+    if (!tstate) {
         return _Py_INIT_ERR("failed to read thread state");
-    interp = tstate->interp;
-    if (!interp)
+    }
+    PyInterpreterState *interp = tstate->interp;
+    if (!interp) {
         return _Py_INIT_ERR("failed to get interpreter");
+    }
+    _PyCoreConfig *core_config = &interp->core_config;
 
     /* Now finish configuring the main interpreter */
     if (_PyMainInterpreterConfig_Copy(&interp->config, config) < 0) {
@@ -834,7 +827,7 @@
         return _Py_ReconfigureMainInterpreter(interp, config);
     }
 
-    if (interp->core_config._disable_importlib) {
+    if (!core_config->_install_importlib) {
         /* Special mode for freeze_importlib: run with no import system
          *
          * This means anything which needs support from extension modules
@@ -852,13 +845,13 @@
         return _Py_INIT_ERR("can't finish initializing sys");
     }
 
-    err = initexternalimport(interp);
+    _PyInitError err = initexternalimport(interp);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
 
     /* initialize the faulthandler module */
-    err = _PyFaulthandler_Init(interp->core_config.faulthandler);
+    err = _PyFaulthandler_Init(core_config->faulthandler);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
@@ -875,8 +868,9 @@
         }
     }
 
-    if (_PyTraceMalloc_Init(interp->core_config.tracemalloc) < 0)
+    if (_PyTraceMalloc_Init(core_config->tracemalloc) < 0) {
         return _Py_INIT_ERR("can't initialize tracemalloc");
+    }
 
     err = add_main_module(interp);
     if (_Py_INIT_FAILED(err)) {
@@ -902,7 +896,7 @@
 
     _PyRuntime.initialized = 1;
 
-    if (!Py_NoSiteFlag) {
+    if (core_config->site_import) {
         err = initsite(); /* Module site */
         if (_Py_INIT_FAILED(err)) {
             return err;
@@ -924,11 +918,10 @@
     _PyCoreConfig config = _PyCoreConfig_INIT;
     _PyInitError err;
 
-    config.ignore_environment = Py_IgnoreEnvironmentFlag;
-    config._disable_importlib = !install_importlib;
+    config._install_importlib = install_importlib;
     config.install_signal_handlers = install_sigs;
 
-    err = _PyCoreConfig_Read(&config, &Py_IsolatedFlag, &Py_NoSiteFlag);
+    err = _PyCoreConfig_Read(&config);
     if (_Py_INIT_FAILED(err)) {
         goto done;
     }
@@ -1320,6 +1313,7 @@
     if (_PyCoreConfig_Copy(&interp->core_config, core_config) < 0) {
         return _Py_INIT_ERR("failed to copy core config");
     }
+    core_config = &interp->core_config;
     if (_PyMainInterpreterConfig_Copy(&interp->config, config) < 0) {
         return _Py_INIT_ERR("failed to copy main interpreter config");
     }
@@ -1395,7 +1389,7 @@
             return err;
         }
 
-        if (!Py_NoSiteFlag) {
+        if (core_config->site_import) {
             err = initsite();
             if (_Py_INIT_FAILED(err)) {
                 return err;