/* Module definition and import implementation */

#include "Python.h"

#include "pycore_import.h"        // _PyImport_BootstrapImp()
#include "pycore_initconfig.h"    // _PyStatus_OK()
#include "pycore_interp.h"        // _PyInterpreterState_ClearModules()
#include "pycore_namespace.h"     // _PyNamespace_Type
#include "pycore_pyerrors.h"      // _PyErr_SetString()
#include "pycore_pyhash.h"        // _Py_KeyedHash()
#include "pycore_pylifecycle.h"
#include "pycore_pymem.h"         // _PyMem_SetDefaultAllocator()
#include "pycore_pystate.h"       // _PyInterpreterState_GET()
#include "pycore_sysmodule.h"     // _PySys_Audit()
#include "marshal.h"              // PyMarshal_ReadObjectFromString()
#include "importdl.h"             // _PyImport_DynLoadFiletab
#include "pydtrace.h"             // PyDTrace_IMPORT_FIND_LOAD_START_ENABLED()
#include <stdbool.h>              // bool

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif

/* Forward references */
static PyObject *import_add_module(PyThreadState *tstate, PyObject *name);

/* This table is defined in config.c: */
extern struct _inittab _PyImport_Inittab[];

// This is not used after Py_Initialize() is called.
// (See _PyRuntimeState.imports.inittab.)
struct _inittab *PyImport_Inittab = _PyImport_Inittab;
// When we dynamically allocate a larger table for PyImport_ExtendInittab(),
// we track the pointer here so we can deallocate it during finalization.
static struct _inittab *inittab_copy = NULL;

/*[clinic input]
module _imp
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=9c332475d8686284]*/

#include "clinic/import.c.h"

/* Initialize things */

PyStatus
_PyImportZip_Init(PyThreadState *tstate)
{
    PyObject *path_hooks;
    int err = 0;

    path_hooks = PySys_GetObject("path_hooks");
    if (path_hooks == NULL) {
        _PyErr_SetString(tstate, PyExc_RuntimeError,
                         "unable to get sys.path_hooks");
        goto error;
    }

    int verbose = _PyInterpreterState_GetConfig(tstate->interp)->verbose;
    if (verbose) {
        PySys_WriteStderr("# installing zipimport hook\n");
    }

    PyObject *zipimporter = _PyImport_GetModuleAttrString("zipimport", "zipimporter");
    if (zipimporter == NULL) {
        _PyErr_Clear(tstate); /* No zipimporter object -- okay */
        if (verbose) {
            PySys_WriteStderr("# can't import zipimport.zipimporter\n");
        }
    }
    else {
        /* sys.path_hooks.insert(0, zipimporter) */
        err = PyList_Insert(path_hooks, 0, zipimporter);
        Py_DECREF(zipimporter);
        if (err < 0) {
            goto error;
        }
        if (verbose) {
            PySys_WriteStderr("# installed zipimport hook\n");
        }
    }

    return _PyStatus_OK();

  error:
    PyErr_Print();
    return _PyStatus_ERR("initializing zipimport failed");
}

/* Locking primitives to prevent parallel imports of the same module
   in different threads to return with a partially loaded module.
   These calls are serialized by the global interpreter lock. */

#define import_lock _PyRuntime.imports.lock.mutex
#define import_lock_thread _PyRuntime.imports.lock.thread
#define import_lock_level _PyRuntime.imports.lock.level

void
_PyImport_AcquireLock(void)
{
    unsigned long me = PyThread_get_thread_ident();
    if (me == PYTHREAD_INVALID_THREAD_ID)
        return; /* Too bad */
    if (import_lock == NULL) {
        import_lock = PyThread_allocate_lock();
        if (import_lock == NULL)
            return;  /* Nothing much we can do. */
    }
    if (import_lock_thread == me) {
        import_lock_level++;
        return;
    }
    if (import_lock_thread != PYTHREAD_INVALID_THREAD_ID ||
        !PyThread_acquire_lock(import_lock, 0))
    {
        PyThreadState *tstate = PyEval_SaveThread();
        PyThread_acquire_lock(import_lock, WAIT_LOCK);
        PyEval_RestoreThread(tstate);
    }
    assert(import_lock_level == 0);
    import_lock_thread = me;
    import_lock_level = 1;
}

int
_PyImport_ReleaseLock(void)
{
    unsigned long me = PyThread_get_thread_ident();
    if (me == PYTHREAD_INVALID_THREAD_ID || import_lock == NULL)
        return 0; /* Too bad */
    if (import_lock_thread != me)
        return -1;
    import_lock_level--;
    assert(import_lock_level >= 0);
    if (import_lock_level == 0) {
        import_lock_thread = PYTHREAD_INVALID_THREAD_ID;
        PyThread_release_lock(import_lock);
    }
    return 1;
}

#ifdef HAVE_FORK
/* This function is called from PyOS_AfterFork_Child() to ensure that newly
   created child processes do not share locks with the parent.
   We now acquire the import lock around fork() calls but on some platforms
   (Solaris 9 and earlier? see isue7242) that still left us with problems. */
PyStatus
_PyImport_ReInitLock(void)
{
    if (import_lock != NULL) {
        if (_PyThread_at_fork_reinit(&import_lock) < 0) {
            return _PyStatus_ERR("failed to create a new lock");
        }
    }

    if (import_lock_level > 1) {
        /* Forked as a side effect of import */
        unsigned long me = PyThread_get_thread_ident();
        PyThread_acquire_lock(import_lock, WAIT_LOCK);
        import_lock_thread = me;
        import_lock_level--;
    } else {
        import_lock_thread = PYTHREAD_INVALID_THREAD_ID;
        import_lock_level = 0;
    }
    return _PyStatus_OK();
}
#endif

/*[clinic input]
_imp.lock_held

Return True if the import lock is currently held, else False.

On platforms without threads, return False.
[clinic start generated code]*/

static PyObject *
_imp_lock_held_impl(PyObject *module)
/*[clinic end generated code: output=8b89384b5e1963fc input=9b088f9b217d9bdf]*/
{
    return PyBool_FromLong(import_lock_thread != PYTHREAD_INVALID_THREAD_ID);
}

/*[clinic input]
_imp.acquire_lock

Acquires the interpreter's import lock for the current thread.

This lock should be used by import hooks to ensure thread-safety when importing
modules. On platforms without threads, this function does nothing.
[clinic start generated code]*/

static PyObject *
_imp_acquire_lock_impl(PyObject *module)
/*[clinic end generated code: output=1aff58cb0ee1b026 input=4a2d4381866d5fdc]*/
{
    _PyImport_AcquireLock();
    Py_RETURN_NONE;
}

/*[clinic input]
_imp.release_lock

Release the interpreter's import lock.

On platforms without threads, this function does nothing.
[clinic start generated code]*/

static PyObject *
_imp_release_lock_impl(PyObject *module)
/*[clinic end generated code: output=7faab6d0be178b0a input=934fb11516dd778b]*/
{
    if (_PyImport_ReleaseLock() < 0) {
        PyErr_SetString(PyExc_RuntimeError,
                        "not holding the import lock");
        return NULL;
    }
    Py_RETURN_NONE;
}

PyStatus
_PyImport_Init(void)
{
    if (_PyRuntime.imports.inittab != NULL) {
        return _PyStatus_ERR("global import state already initialized");
    }
    PyStatus status = _PyStatus_OK();

    size_t size;
    for (size = 0; PyImport_Inittab[size].name != NULL; size++)
        ;
    size++;

    /* Force default raw memory allocator to get a known allocator to be able
       to release the memory in _PyImport_Fini() */
    PyMemAllocatorEx old_alloc;
    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);

    /* Make the copy. */
    struct _inittab *copied = PyMem_RawMalloc(size * sizeof(struct _inittab));
    if (copied == NULL) {
        status = PyStatus_NoMemory();
        goto done;
    }
    memcpy(copied, PyImport_Inittab, size * sizeof(struct _inittab));
    _PyRuntime.imports.inittab = copied;

done:
    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
    return status;
}

static inline void _extensions_cache_clear(void);

void
_PyImport_Fini(void)
{
    _extensions_cache_clear();
    if (import_lock != NULL) {
        PyThread_free_lock(import_lock);
        import_lock = NULL;
    }

    /* Use the same memory allocator as _PyImport_Init(). */
    PyMemAllocatorEx old_alloc;
    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);

    /* Free memory allocated by _PyImport_Init() */
    struct _inittab *inittab = _PyRuntime.imports.inittab;
    _PyRuntime.imports.inittab = NULL;
    PyMem_RawFree(inittab);

    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
}

void
_PyImport_Fini2(void)
{
    /* Use the same memory allocator than PyImport_ExtendInittab(). */
    PyMemAllocatorEx old_alloc;
    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);

    // Reset PyImport_Inittab
    PyImport_Inittab = _PyImport_Inittab;

    /* Free memory allocated by PyImport_ExtendInittab() */
    PyMem_RawFree(inittab_copy);
    inittab_copy = NULL;

    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
}

/* Helper for sys */

PyObject *
PyImport_GetModuleDict(void)
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    if (interp->modules == NULL) {
        Py_FatalError("interpreter has no modules dictionary");
    }
    return interp->modules;
}

/* In some corner cases it is important to be sure that the import
   machinery has been initialized (or not cleaned up yet).  For
   example, see issue #4236 and PyModule_Create2(). */

int
_PyImport_IsInitialized(PyInterpreterState *interp)
{
    if (interp->modules == NULL)
        return 0;
    return 1;
}

PyObject *
_PyImport_GetModuleId(_Py_Identifier *nameid)
{
    PyObject *name = _PyUnicode_FromId(nameid); /* borrowed */
    if (name == NULL) {
        return NULL;
    }
    return PyImport_GetModule(name);
}

int
_PyImport_SetModule(PyObject *name, PyObject *m)
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    PyObject *modules = interp->modules;
    return PyObject_SetItem(modules, name, m);
}

int
_PyImport_SetModuleString(const char *name, PyObject *m)
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    PyObject *modules = interp->modules;
    return PyMapping_SetItemString(modules, name, m);
}

static PyObject *
import_get_module(PyThreadState *tstate, PyObject *name)
{
    PyObject *modules = tstate->interp->modules;
    if (modules == NULL) {
        _PyErr_SetString(tstate, PyExc_RuntimeError,
                         "unable to get sys.modules");
        return NULL;
    }

    PyObject *m;
    Py_INCREF(modules);
    if (PyDict_CheckExact(modules)) {
        m = PyDict_GetItemWithError(modules, name);  /* borrowed */
        Py_XINCREF(m);
    }
    else {
        m = PyObject_GetItem(modules, name);
        if (m == NULL && _PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
            _PyErr_Clear(tstate);
        }
    }
    Py_DECREF(modules);
    return m;
}


static int
import_ensure_initialized(PyInterpreterState *interp, PyObject *mod, PyObject *name)
{
    PyObject *spec;

    /* Optimization: only call _bootstrap._lock_unlock_module() if
       __spec__._initializing is true.
       NOTE: because of this, initializing must be set *before*
       stuffing the new module in sys.modules.
    */
    spec = PyObject_GetAttr(mod, &_Py_ID(__spec__));
    int busy = _PyModuleSpec_IsInitializing(spec);
    Py_XDECREF(spec);
    if (busy) {
        /* Wait until module is done importing. */
        PyObject *value = _PyObject_CallMethodOneArg(
            interp->importlib, &_Py_ID(_lock_unlock_module), name);
        if (value == NULL) {
            return -1;
        }
        Py_DECREF(value);
    }
    return 0;
}


/* Helper for pythonrun.c -- return magic number and tag. */

long
PyImport_GetMagicNumber(void)
{
    long res;
    PyInterpreterState *interp = _PyInterpreterState_GET();
    PyObject *external, *pyc_magic;

    external = PyObject_GetAttrString(interp->importlib, "_bootstrap_external");
    if (external == NULL)
        return -1;
    pyc_magic = PyObject_GetAttrString(external, "_RAW_MAGIC_NUMBER");
    Py_DECREF(external);
    if (pyc_magic == NULL)
        return -1;
    res = PyLong_AsLong(pyc_magic);
    Py_DECREF(pyc_magic);
    return res;
}


extern const char * _PySys_ImplCacheTag;

const char *
PyImport_GetMagicTag(void)
{
    return _PySys_ImplCacheTag;
}


/* Magic for extension modules (built-in as well as dynamically
   loaded).  To prevent initializing an extension module more than
   once, we keep a static dictionary 'extensions' keyed by the tuple
   (module name, module name)  (for built-in modules) or by
   (filename, module name) (for dynamically loaded modules), containing these
   modules.  A copy of the module's dictionary is stored by calling
   _PyImport_FixupExtensionObject() immediately after the module initialization
   function succeeds.  A copy can be retrieved from there by calling
   import_find_extension().

   Modules which do support multiple initialization set their m_size
   field to a non-negative number (indicating the size of the
   module-specific state). They are still recorded in the extensions
   dictionary, to avoid loading shared libraries twice.
*/

static PyModuleDef *
_extensions_cache_get(PyObject *filename, PyObject *name)
{
    PyObject *extensions = _PyRuntime.imports.extensions;
    if (extensions == NULL) {
        return NULL;
    }
    PyObject *key = PyTuple_Pack(2, filename, name);
    if (key == NULL) {
        return NULL;
    }
    PyModuleDef *def = (PyModuleDef *)PyDict_GetItemWithError(extensions, key);
    Py_DECREF(key);
    return def;
}

static int
_extensions_cache_set(PyObject *filename, PyObject *name, PyModuleDef *def)
{
    PyObject *extensions = _PyRuntime.imports.extensions;
    if (extensions == NULL) {
        extensions = PyDict_New();
        if (extensions == NULL) {
            return -1;
        }
        _PyRuntime.imports.extensions = extensions;
    }
    PyObject *key = PyTuple_Pack(2, filename, name);
    if (key == NULL) {
        return -1;
    }
    int res = PyDict_SetItem(extensions, key, (PyObject *)def);
    Py_DECREF(key);
    if (res < 0) {
        return -1;
    }
    return 0;
}

static void
_extensions_cache_clear(void)
{
    Py_CLEAR(_PyRuntime.imports.extensions);
}

int
_PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
                               PyObject *filename, PyObject *modules)
{
    if (mod == NULL || !PyModule_Check(mod)) {
        PyErr_BadInternalCall();
        return -1;
    }

    struct PyModuleDef *def = PyModule_GetDef(mod);
    if (!def) {
        PyErr_BadInternalCall();
        return -1;
    }

    PyThreadState *tstate = _PyThreadState_GET();
    if (PyObject_SetItem(modules, name, mod) < 0) {
        return -1;
    }
    if (_PyState_AddModule(tstate, mod, def) < 0) {
        PyMapping_DelItem(modules, name);
        return -1;
    }

    // bpo-44050: Extensions and def->m_base.m_copy can be updated
    // when the extension module doesn't support sub-interpreters.
    if (_Py_IsMainInterpreter(tstate->interp) || def->m_size == -1) {
        if (def->m_size == -1) {
            if (def->m_base.m_copy) {
                /* Somebody already imported the module,
                   likely under a different name.
                   XXX this should really not happen. */
                Py_CLEAR(def->m_base.m_copy);
            }
            PyObject *dict = PyModule_GetDict(mod);
            if (dict == NULL) {
                return -1;
            }
            def->m_base.m_copy = PyDict_Copy(dict);
            if (def->m_base.m_copy == NULL) {
                return -1;
            }
        }

        if (_extensions_cache_set(filename, name, def) < 0) {
            return -1;
        }
    }

    return 0;
}

int
_PyImport_FixupBuiltin(PyObject *mod, const char *name, PyObject *modules)
{
    int res;
    PyObject *nameobj;
    nameobj = PyUnicode_InternFromString(name);
    if (nameobj == NULL)
        return -1;
    res = _PyImport_FixupExtensionObject(mod, nameobj, nameobj, modules);
    Py_DECREF(nameobj);
    return res;
}

static PyObject *
import_find_extension(PyThreadState *tstate, PyObject *name,
                      PyObject *filename)
{
    PyModuleDef *def = _extensions_cache_get(filename, name);
    if (def == NULL) {
        return NULL;
    }

    PyObject *mod, *mdict;
    PyObject *modules = tstate->interp->modules;

    if (def->m_size == -1) {
        /* Module does not support repeated initialization */
        if (def->m_base.m_copy == NULL)
            return NULL;
        mod = import_add_module(tstate, name);
        if (mod == NULL)
            return NULL;
        mdict = PyModule_GetDict(mod);
        if (mdict == NULL) {
            Py_DECREF(mod);
            return NULL;
        }
        if (PyDict_Update(mdict, def->m_base.m_copy)) {
            Py_DECREF(mod);
            return NULL;
        }
    }
    else {
        if (def->m_base.m_init == NULL)
            return NULL;
        mod = _PyImport_InitFunc_TrampolineCall(def->m_base.m_init);
        if (mod == NULL)
            return NULL;
        if (PyObject_SetItem(modules, name, mod) == -1) {
            Py_DECREF(mod);
            return NULL;
        }
    }
    if (_PyState_AddModule(tstate, mod, def) < 0) {
        PyMapping_DelItem(modules, name);
        Py_DECREF(mod);
        return NULL;
    }

    int verbose = _PyInterpreterState_GetConfig(tstate->interp)->verbose;
    if (verbose) {
        PySys_FormatStderr("import %U # previously loaded (%R)\n",
                           name, filename);
    }
    return mod;
}


/* Get the module object corresponding to a module name.
   First check the modules dictionary if there's one there,
   if not, create a new one and insert it in the modules dictionary. */

static PyObject *
import_add_module(PyThreadState *tstate, PyObject *name)
{
    PyObject *modules = tstate->interp->modules;
    if (modules == NULL) {
        _PyErr_SetString(tstate, PyExc_RuntimeError,
                         "no import module dictionary");
        return NULL;
    }

    PyObject *m;
    if (PyDict_CheckExact(modules)) {
        m = Py_XNewRef(PyDict_GetItemWithError(modules, name));
    }
    else {
        m = PyObject_GetItem(modules, name);
        // For backward-compatibility we copy the behavior
        // of PyDict_GetItemWithError().
        if (_PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
            _PyErr_Clear(tstate);
        }
    }
    if (_PyErr_Occurred(tstate)) {
        return NULL;
    }
    if (m != NULL && PyModule_Check(m)) {
        return m;
    }
    Py_XDECREF(m);
    m = PyModule_NewObject(name);
    if (m == NULL)
        return NULL;
    if (PyObject_SetItem(modules, name, m) != 0) {
        Py_DECREF(m);
        return NULL;
    }

    return m;
}

PyObject *
PyImport_AddModuleObject(PyObject *name)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *mod = import_add_module(tstate, name);
    if (mod) {
        PyObject *ref = PyWeakref_NewRef(mod, NULL);
        Py_DECREF(mod);
        if (ref == NULL) {
            return NULL;
        }
        mod = PyWeakref_GetObject(ref);
        Py_DECREF(ref);
    }
    return mod; /* borrowed reference */
}


PyObject *
PyImport_AddModule(const char *name)
{
    PyObject *nameobj = PyUnicode_FromString(name);
    if (nameobj == NULL) {
        return NULL;
    }
    PyObject *module = PyImport_AddModuleObject(nameobj);
    Py_DECREF(nameobj);
    return module;
}


/* Remove name from sys.modules, if it's there.
 * Can be called with an exception raised.
 * If fail to remove name a new exception will be chained with the old
 * exception, otherwise the old exception is preserved.
 */
static void
remove_module(PyThreadState *tstate, PyObject *name)
{
    PyObject *type, *value, *traceback;
    _PyErr_Fetch(tstate, &type, &value, &traceback);

    PyObject *modules = tstate->interp->modules;
    if (PyDict_CheckExact(modules)) {
        PyObject *mod = _PyDict_Pop(modules, name, Py_None);
        Py_XDECREF(mod);
    }
    else if (PyMapping_DelItem(modules, name) < 0) {
        if (_PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
            _PyErr_Clear(tstate);
        }
    }

    _PyErr_ChainExceptions(type, value, traceback);
}


/* Execute a code object in a module and return the module object
 * WITH INCREMENTED REFERENCE COUNT.  If an error occurs, name is
 * removed from sys.modules, to avoid leaving damaged module objects
 * in sys.modules.  The caller may wish to restore the original
 * module object (if any) in this case; PyImport_ReloadModule is an
 * example.
 *
 * Note that PyImport_ExecCodeModuleWithPathnames() is the preferred, richer
 * interface.  The other two exist primarily for backward compatibility.
 */
PyObject *
PyImport_ExecCodeModule(const char *name, PyObject *co)
{
    return PyImport_ExecCodeModuleWithPathnames(
        name, co, (char *)NULL, (char *)NULL);
}

PyObject *
PyImport_ExecCodeModuleEx(const char *name, PyObject *co, const char *pathname)
{
    return PyImport_ExecCodeModuleWithPathnames(
        name, co, pathname, (char *)NULL);
}

PyObject *
PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co,
                                     const char *pathname,
                                     const char *cpathname)
{
    PyObject *m = NULL;
    PyObject *nameobj, *pathobj = NULL, *cpathobj = NULL, *external= NULL;

    nameobj = PyUnicode_FromString(name);
    if (nameobj == NULL)
        return NULL;

    if (cpathname != NULL) {
        cpathobj = PyUnicode_DecodeFSDefault(cpathname);
        if (cpathobj == NULL)
            goto error;
    }
    else
        cpathobj = NULL;

    if (pathname != NULL) {
        pathobj = PyUnicode_DecodeFSDefault(pathname);
        if (pathobj == NULL)
            goto error;
    }
    else if (cpathobj != NULL) {
        PyInterpreterState *interp = _PyInterpreterState_GET();

        if (interp == NULL) {
            Py_FatalError("no current interpreter");
        }

        external= PyObject_GetAttrString(interp->importlib,
                                         "_bootstrap_external");
        if (external != NULL) {
            pathobj = _PyObject_CallMethodOneArg(
                external, &_Py_ID(_get_sourcefile), cpathobj);
            Py_DECREF(external);
        }
        if (pathobj == NULL)
            PyErr_Clear();
    }
    else
        pathobj = NULL;

    m = PyImport_ExecCodeModuleObject(nameobj, co, pathobj, cpathobj);
error:
    Py_DECREF(nameobj);
    Py_XDECREF(pathobj);
    Py_XDECREF(cpathobj);
    return m;
}

static PyObject *
module_dict_for_exec(PyThreadState *tstate, PyObject *name)
{
    PyObject *m, *d;

    m = import_add_module(tstate, name);
    if (m == NULL)
        return NULL;
    /* If the module is being reloaded, we get the old module back
       and re-use its dict to exec the new code. */
    d = PyModule_GetDict(m);
    int r = PyDict_Contains(d, &_Py_ID(__builtins__));
    if (r == 0) {
        r = PyDict_SetItem(d, &_Py_ID(__builtins__), PyEval_GetBuiltins());
    }
    if (r < 0) {
        remove_module(tstate, name);
        Py_DECREF(m);
        return NULL;
    }

    Py_INCREF(d);
    Py_DECREF(m);
    return d;
}

static PyObject *
exec_code_in_module(PyThreadState *tstate, PyObject *name,
                    PyObject *module_dict, PyObject *code_object)
{
    PyObject *v, *m;

    v = PyEval_EvalCode(code_object, module_dict, module_dict);
    if (v == NULL) {
        remove_module(tstate, name);
        return NULL;
    }
    Py_DECREF(v);

    m = import_get_module(tstate, name);
    if (m == NULL && !_PyErr_Occurred(tstate)) {
        _PyErr_Format(tstate, PyExc_ImportError,
                      "Loaded module %R not found in sys.modules",
                      name);
    }

    return m;
}

PyObject*
PyImport_ExecCodeModuleObject(PyObject *name, PyObject *co, PyObject *pathname,
                              PyObject *cpathname)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *d, *external, *res;

    d = module_dict_for_exec(tstate, name);
    if (d == NULL) {
        return NULL;
    }

    if (pathname == NULL) {
        pathname = ((PyCodeObject *)co)->co_filename;
    }
    external = PyObject_GetAttrString(tstate->interp->importlib,
                                      "_bootstrap_external");
    if (external == NULL) {
        Py_DECREF(d);
        return NULL;
    }
    res = PyObject_CallMethodObjArgs(external, &_Py_ID(_fix_up_module),
                                     d, name, pathname, cpathname, NULL);
    Py_DECREF(external);
    if (res != NULL) {
        Py_DECREF(res);
        res = exec_code_in_module(tstate, name, d, co);
    }
    Py_DECREF(d);
    return res;
}


static void
update_code_filenames(PyCodeObject *co, PyObject *oldname, PyObject *newname)
{
    PyObject *constants, *tmp;
    Py_ssize_t i, n;

    if (PyUnicode_Compare(co->co_filename, oldname))
        return;

    Py_XSETREF(co->co_filename, Py_NewRef(newname));

    constants = co->co_consts;
    n = PyTuple_GET_SIZE(constants);
    for (i = 0; i < n; i++) {
        tmp = PyTuple_GET_ITEM(constants, i);
        if (PyCode_Check(tmp))
            update_code_filenames((PyCodeObject *)tmp,
                                  oldname, newname);
    }
}

static void
update_compiled_module(PyCodeObject *co, PyObject *newname)
{
    PyObject *oldname;

    if (PyUnicode_Compare(co->co_filename, newname) == 0)
        return;

    oldname = co->co_filename;
    Py_INCREF(oldname);
    update_code_filenames(co, oldname, newname);
    Py_DECREF(oldname);
}

/*[clinic input]
_imp._fix_co_filename

    code: object(type="PyCodeObject *", subclass_of="&PyCode_Type")
        Code object to change.

    path: unicode
        File path to use.
    /

Changes code.co_filename to specify the passed-in file path.
[clinic start generated code]*/

static PyObject *
_imp__fix_co_filename_impl(PyObject *module, PyCodeObject *code,
                           PyObject *path)
/*[clinic end generated code: output=1d002f100235587d input=895ba50e78b82f05]*/

{
    update_compiled_module(code, path);

    Py_RETURN_NONE;
}


/* Helper to test for built-in module */

static int
is_builtin(PyObject *name)
{
    int i;
    struct _inittab *inittab = _PyRuntime.imports.inittab;
    for (i = 0; inittab[i].name != NULL; i++) {
        if (_PyUnicode_EqualToASCIIString(name, inittab[i].name)) {
            if (inittab[i].initfunc == NULL)
                return -1;
            else
                return 1;
        }
    }
    return 0;
}


/* Return a finder object for a sys.path/pkg.__path__ item 'p',
   possibly by fetching it from the path_importer_cache dict. If it
   wasn't yet cached, traverse path_hooks until a hook is found
   that can handle the path item. Return None if no hook could;
   this tells our caller that the path based finder could not find
   a finder for this path item. Cache the result in
   path_importer_cache. */

static PyObject *
get_path_importer(PyThreadState *tstate, PyObject *path_importer_cache,
                  PyObject *path_hooks, PyObject *p)
{
    PyObject *importer;
    Py_ssize_t j, nhooks;

    /* These conditions are the caller's responsibility: */
    assert(PyList_Check(path_hooks));
    assert(PyDict_Check(path_importer_cache));

    nhooks = PyList_Size(path_hooks);
    if (nhooks < 0)
        return NULL; /* Shouldn't happen */

    importer = PyDict_GetItemWithError(path_importer_cache, p);
    if (importer != NULL || _PyErr_Occurred(tstate)) {
        return Py_XNewRef(importer);
    }

    /* set path_importer_cache[p] to None to avoid recursion */
    if (PyDict_SetItem(path_importer_cache, p, Py_None) != 0)
        return NULL;

    for (j = 0; j < nhooks; j++) {
        PyObject *hook = PyList_GetItem(path_hooks, j);
        if (hook == NULL)
            return NULL;
        importer = PyObject_CallOneArg(hook, p);
        if (importer != NULL)
            break;

        if (!_PyErr_ExceptionMatches(tstate, PyExc_ImportError)) {
            return NULL;
        }
        _PyErr_Clear(tstate);
    }
    if (importer == NULL) {
        Py_RETURN_NONE;
    }
    if (PyDict_SetItem(path_importer_cache, p, importer) < 0) {
        Py_DECREF(importer);
        return NULL;
    }
    return importer;
}

PyObject *
PyImport_GetImporter(PyObject *path)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *path_importer_cache = PySys_GetObject("path_importer_cache");
    PyObject *path_hooks = PySys_GetObject("path_hooks");
    if (path_importer_cache == NULL || path_hooks == NULL) {
        return NULL;
    }
    return get_path_importer(tstate, path_importer_cache, path_hooks, path);
}

#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
#include <emscripten.h>
EM_JS(PyObject*, _PyImport_InitFunc_TrampolineCall, (PyModInitFunction func), {
    return wasmTable.get(func)();
});
#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE

static PyObject*
create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
{
    PyObject *mod = import_find_extension(tstate, name, name);
    if (mod || _PyErr_Occurred(tstate)) {
        return mod;
    }

    PyObject *modules = tstate->interp->modules;
    for (struct _inittab *p = _PyRuntime.imports.inittab; p->name != NULL; p++) {
        if (_PyUnicode_EqualToASCIIString(name, p->name)) {
            if (p->initfunc == NULL) {
                /* Cannot re-init internal module ("sys" or "builtins") */
                mod = PyImport_AddModuleObject(name);
                return Py_XNewRef(mod);
            }
            mod = _PyImport_InitFunc_TrampolineCall(*p->initfunc);
            if (mod == NULL) {
                return NULL;
            }

            if (PyObject_TypeCheck(mod, &PyModuleDef_Type)) {
                return PyModule_FromDefAndSpec((PyModuleDef*)mod, spec);
            }
            else {
                /* Remember pointer to module init function. */
                PyModuleDef *def = PyModule_GetDef(mod);
                if (def == NULL) {
                    return NULL;
                }

                def->m_base.m_init = p->initfunc;
                if (_PyImport_FixupExtensionObject(mod, name, name,
                                                   modules) < 0) {
                    return NULL;
                }
                return mod;
            }
        }
    }

    // not found
    Py_RETURN_NONE;
}


/*[clinic input]
_imp.create_builtin

    spec: object
    /

Create an extension module.
[clinic start generated code]*/

static PyObject *
_imp_create_builtin(PyObject *module, PyObject *spec)
/*[clinic end generated code: output=ace7ff22271e6f39 input=37f966f890384e47]*/
{
    PyThreadState *tstate = _PyThreadState_GET();

    PyObject *name = PyObject_GetAttrString(spec, "name");
    if (name == NULL) {
        return NULL;
    }

    if (!PyUnicode_Check(name)) {
        PyErr_Format(PyExc_TypeError,
                     "name must be string, not %.200s",
                     Py_TYPE(name)->tp_name);
        Py_DECREF(name);
        return NULL;
    }

    PyObject *mod = create_builtin(tstate, name, spec);
    Py_DECREF(name);
    return mod;
}


/* Return true if the name is an alias.  In that case, "alias" is set
   to the original module name.  If it is an alias but the original
   module isn't known then "alias" is set to NULL while true is returned. */
static bool
resolve_module_alias(const char *name, const struct _module_alias *aliases,
                     const char **alias)
{
    const struct _module_alias *entry;
    for (entry = aliases; ; entry++) {
        if (entry->name == NULL) {
            /* It isn't an alias. */
            return false;
        }
        if (strcmp(name, entry->name) == 0) {
            if (alias != NULL) {
                *alias = entry->orig;
            }
            return true;
        }
    }
}


/* Frozen modules */

static bool
use_frozen(void)
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    int override = interp->override_frozen_modules;
    if (override > 0) {
        return true;
    }
    else if (override < 0) {
        return false;
    }
    else {
        return interp->config.use_frozen_modules;
    }
}

static PyObject *
list_frozen_module_names(void)
{
    PyObject *names = PyList_New(0);
    if (names == NULL) {
        return NULL;
    }
    bool enabled = use_frozen();
    const struct _frozen *p;
#define ADD_MODULE(name) \
    do { \
        PyObject *nameobj = PyUnicode_FromString(name); \
        if (nameobj == NULL) { \
            goto error; \
        } \
        int res = PyList_Append(names, nameobj); \
        Py_DECREF(nameobj); \
        if (res != 0) { \
            goto error; \
        } \
    } while(0)
    // We always use the bootstrap modules.
    for (p = _PyImport_FrozenBootstrap; ; p++) {
        if (p->name == NULL) {
            break;
        }
        ADD_MODULE(p->name);
    }
    // Frozen stdlib modules may be disabled.
    for (p = _PyImport_FrozenStdlib; ; p++) {
        if (p->name == NULL) {
            break;
        }
        if (enabled) {
            ADD_MODULE(p->name);
        }
    }
    for (p = _PyImport_FrozenTest; ; p++) {
        if (p->name == NULL) {
            break;
        }
        if (enabled) {
            ADD_MODULE(p->name);
        }
    }
#undef ADD_MODULE
    // Add any custom modules.
    if (PyImport_FrozenModules != NULL) {
        for (p = PyImport_FrozenModules; ; p++) {
            if (p->name == NULL) {
                break;
            }
            PyObject *nameobj = PyUnicode_FromString(p->name);
            if (nameobj == NULL) {
                goto error;
            }
            int found = PySequence_Contains(names, nameobj);
            if (found < 0) {
                Py_DECREF(nameobj);
                goto error;
            }
            else if (found) {
                Py_DECREF(nameobj);
            }
            else {
                int res = PyList_Append(names, nameobj);
                Py_DECREF(nameobj);
                if (res != 0) {
                    goto error;
                }
            }
        }
    }
    return names;

error:
    Py_DECREF(names);
    return NULL;
}

typedef enum {
    FROZEN_OKAY,
    FROZEN_BAD_NAME,    // The given module name wasn't valid.
    FROZEN_NOT_FOUND,   // It wasn't in PyImport_FrozenModules.
    FROZEN_DISABLED,    // -X frozen_modules=off (and not essential)
    FROZEN_EXCLUDED,    /* The PyImport_FrozenModules entry has NULL "code"
                           (module is present but marked as unimportable, stops search). */
    FROZEN_INVALID,     /* The PyImport_FrozenModules entry is bogus
                           (eg. does not contain executable code). */
} frozen_status;

static inline void
set_frozen_error(frozen_status status, PyObject *modname)
{
    const char *err = NULL;
    switch (status) {
        case FROZEN_BAD_NAME:
        case FROZEN_NOT_FOUND:
            err = "No such frozen object named %R";
            break;
        case FROZEN_DISABLED:
            err = "Frozen modules are disabled and the frozen object named %R is not essential";
            break;
        case FROZEN_EXCLUDED:
            err = "Excluded frozen object named %R";
            break;
        case FROZEN_INVALID:
            err = "Frozen object named %R is invalid";
            break;
        case FROZEN_OKAY:
            // There was no error.
            break;
        default:
            Py_UNREACHABLE();
    }
    if (err != NULL) {
        PyObject *msg = PyUnicode_FromFormat(err, modname);
        if (msg == NULL) {
            PyErr_Clear();
        }
        PyErr_SetImportError(msg, modname, NULL);
        Py_XDECREF(msg);
    }
}

static const struct _frozen *
look_up_frozen(const char *name)
{
    const struct _frozen *p;
    // We always use the bootstrap modules.
    for (p = _PyImport_FrozenBootstrap; ; p++) {
        if (p->name == NULL) {
            // We hit the end-of-list sentinel value.
            break;
        }
        if (strcmp(name, p->name) == 0) {
            return p;
        }
    }
    // Prefer custom modules, if any.  Frozen stdlib modules can be
    // disabled here by setting "code" to NULL in the array entry.
    if (PyImport_FrozenModules != NULL) {
        for (p = PyImport_FrozenModules; ; p++) {
            if (p->name == NULL) {
                break;
            }
            if (strcmp(name, p->name) == 0) {
                return p;
            }
        }
    }
    // Frozen stdlib modules may be disabled.
    if (use_frozen()) {
        for (p = _PyImport_FrozenStdlib; ; p++) {
            if (p->name == NULL) {
                break;
            }
            if (strcmp(name, p->name) == 0) {
                return p;
            }
        }
        for (p = _PyImport_FrozenTest; ; p++) {
            if (p->name == NULL) {
                break;
            }
            if (strcmp(name, p->name) == 0) {
                return p;
            }
        }
    }
    return NULL;
}

struct frozen_info {
    PyObject *nameobj;
    const char *data;
    PyObject *(*get_code)(void);
    Py_ssize_t size;
    bool is_package;
    bool is_alias;
    const char *origname;
};

static frozen_status
find_frozen(PyObject *nameobj, struct frozen_info *info)
{
    if (info != NULL) {
        memset(info, 0, sizeof(*info));
    }

    if (nameobj == NULL || nameobj == Py_None) {
        return FROZEN_BAD_NAME;
    }
    const char *name = PyUnicode_AsUTF8(nameobj);
    if (name == NULL) {
        // Note that this function previously used
        // _PyUnicode_EqualToASCIIString().  We clear the error here
        // (instead of propagating it) to match the earlier behavior
        // more closely.
        PyErr_Clear();
        return FROZEN_BAD_NAME;
    }

    const struct _frozen *p = look_up_frozen(name);
    if (p == NULL) {
        return FROZEN_NOT_FOUND;
    }
    if (info != NULL) {
        info->nameobj = nameobj;  // borrowed
        info->data = (const char *)p->code;
        info->get_code = p->get_code;
        info->size = p->size;
        info->is_package = p->is_package;
        if (p->size < 0) {
            // backward compatibility with negative size values
            info->size = -(p->size);
            info->is_package = true;
        }
        info->origname = name;
        info->is_alias = resolve_module_alias(name, _PyImport_FrozenAliases,
                                              &info->origname);
    }
    if (p->code == NULL && p->size == 0 && p->get_code != NULL) {
        /* It is only deepfrozen. */
        return FROZEN_OKAY;
    }
    if (p->code == NULL) {
        /* It is frozen but marked as un-importable. */
        return FROZEN_EXCLUDED;
    }
    if (p->code[0] == '\0' || p->size == 0) {
        /* Does not contain executable code. */
        return FROZEN_INVALID;
    }
    return FROZEN_OKAY;
}

static PyObject *
unmarshal_frozen_code(struct frozen_info *info)
{
    if (info->get_code) {
        PyObject *code = info->get_code();
        assert(code != NULL);
        return code;
    }
    PyObject *co = PyMarshal_ReadObjectFromString(info->data, info->size);
    if (co == NULL) {
        /* Does not contain executable code. */
        set_frozen_error(FROZEN_INVALID, info->nameobj);
        return NULL;
    }
    if (!PyCode_Check(co)) {
        // We stick with TypeError for backward compatibility.
        PyErr_Format(PyExc_TypeError,
                     "frozen object %R is not a code object",
                     info->nameobj);
        Py_DECREF(co);
        return NULL;
    }
    return co;
}


/* Initialize a frozen module.
   Return 1 for success, 0 if the module is not found, and -1 with
   an exception set if the initialization failed.
   This function is also used from frozenmain.c */

int
PyImport_ImportFrozenModuleObject(PyObject *name)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *co, *m, *d = NULL;
    int err;

    struct frozen_info info;
    frozen_status status = find_frozen(name, &info);
    if (status == FROZEN_NOT_FOUND || status == FROZEN_DISABLED) {
        return 0;
    }
    else if (status == FROZEN_BAD_NAME) {
        return 0;
    }
    else if (status != FROZEN_OKAY) {
        set_frozen_error(status, name);
        return -1;
    }
    co = unmarshal_frozen_code(&info);
    if (co == NULL) {
        return -1;
    }
    if (info.is_package) {
        /* Set __path__ to the empty list */
        PyObject *l;
        m = import_add_module(tstate, name);
        if (m == NULL)
            goto err_return;
        d = PyModule_GetDict(m);
        l = PyList_New(0);
        if (l == NULL) {
            Py_DECREF(m);
            goto err_return;
        }
        err = PyDict_SetItemString(d, "__path__", l);
        Py_DECREF(l);
        Py_DECREF(m);
        if (err != 0)
            goto err_return;
    }
    d = module_dict_for_exec(tstate, name);
    if (d == NULL) {
        goto err_return;
    }
    m = exec_code_in_module(tstate, name, d, co);
    if (m == NULL) {
        goto err_return;
    }
    Py_DECREF(m);
    /* Set __origname__ (consumed in FrozenImporter._setup_module()). */
    PyObject *origname;
    if (info.origname) {
        origname = PyUnicode_FromString(info.origname);
        if (origname == NULL) {
            goto err_return;
        }
    }
    else {
        origname = Py_NewRef(Py_None);
    }
    err = PyDict_SetItemString(d, "__origname__", origname);
    Py_DECREF(origname);
    if (err != 0) {
        goto err_return;
    }
    Py_DECREF(d);
    Py_DECREF(co);
    return 1;

err_return:
    Py_XDECREF(d);
    Py_DECREF(co);
    return -1;
}

int
PyImport_ImportFrozenModule(const char *name)
{
    PyObject *nameobj;
    int ret;
    nameobj = PyUnicode_InternFromString(name);
    if (nameobj == NULL)
        return -1;
    ret = PyImport_ImportFrozenModuleObject(nameobj);
    Py_DECREF(nameobj);
    return ret;
}


/* Import a module, either built-in, frozen, or external, and return
   its module object WITH INCREMENTED REFERENCE COUNT */

PyObject *
PyImport_ImportModule(const char *name)
{
    PyObject *pname;
    PyObject *result;

    pname = PyUnicode_FromString(name);
    if (pname == NULL)
        return NULL;
    result = PyImport_Import(pname);
    Py_DECREF(pname);
    return result;
}


/* Import a module without blocking
 *
 * At first it tries to fetch the module from sys.modules. If the module was
 * never loaded before it loads it with PyImport_ImportModule() unless another
 * thread holds the import lock. In the latter case the function raises an
 * ImportError instead of blocking.
 *
 * Returns the module object with incremented ref count.
 */
PyObject *
PyImport_ImportModuleNoBlock(const char *name)
{
    return PyImport_ImportModule(name);
}


/* Remove importlib frames from the traceback,
 * except in Verbose mode. */
static void
remove_importlib_frames(PyThreadState *tstate)
{
    const char *importlib_filename = "<frozen importlib._bootstrap>";
    const char *external_filename = "<frozen importlib._bootstrap_external>";
    const char *remove_frames = "_call_with_frames_removed";
    int always_trim = 0;
    int in_importlib = 0;
    PyObject *exception, *value, *base_tb, *tb;
    PyObject **prev_link, **outer_link = NULL;

    /* Synopsis: if it's an ImportError, we trim all importlib chunks
       from the traceback. We always trim chunks
       which end with a call to "_call_with_frames_removed". */

    _PyErr_Fetch(tstate, &exception, &value, &base_tb);
    if (!exception || _PyInterpreterState_GetConfig(tstate->interp)->verbose) {
        goto done;
    }

    if (PyType_IsSubtype((PyTypeObject *) exception,
                         (PyTypeObject *) PyExc_ImportError))
        always_trim = 1;

    prev_link = &base_tb;
    tb = base_tb;
    while (tb != NULL) {
        PyTracebackObject *traceback = (PyTracebackObject *)tb;
        PyObject *next = (PyObject *) traceback->tb_next;
        PyFrameObject *frame = traceback->tb_frame;
        PyCodeObject *code = PyFrame_GetCode(frame);
        int now_in_importlib;

        assert(PyTraceBack_Check(tb));
        now_in_importlib = _PyUnicode_EqualToASCIIString(code->co_filename, importlib_filename) ||
                           _PyUnicode_EqualToASCIIString(code->co_filename, external_filename);
        if (now_in_importlib && !in_importlib) {
            /* This is the link to this chunk of importlib tracebacks */
            outer_link = prev_link;
        }
        in_importlib = now_in_importlib;

        if (in_importlib &&
            (always_trim ||
             _PyUnicode_EqualToASCIIString(code->co_name, remove_frames))) {
            Py_XSETREF(*outer_link, Py_XNewRef(next));
            prev_link = outer_link;
        }
        else {
            prev_link = (PyObject **) &traceback->tb_next;
        }
        Py_DECREF(code);
        tb = next;
    }
done:
    _PyErr_Restore(tstate, exception, value, base_tb);
}


static PyObject *
resolve_name(PyThreadState *tstate, PyObject *name, PyObject *globals, int level)
{
    PyObject *abs_name;
    PyObject *package = NULL;
    PyObject *spec;
    Py_ssize_t last_dot;
    PyObject *base;
    int level_up;

    if (globals == NULL) {
        _PyErr_SetString(tstate, PyExc_KeyError, "'__name__' not in globals");
        goto error;
    }
    if (!PyDict_Check(globals)) {
        _PyErr_SetString(tstate, PyExc_TypeError, "globals must be a dict");
        goto error;
    }
    package = PyDict_GetItemWithError(globals, &_Py_ID(__package__));
    if (package == Py_None) {
        package = NULL;
    }
    else if (package == NULL && _PyErr_Occurred(tstate)) {
        goto error;
    }
    spec = PyDict_GetItemWithError(globals, &_Py_ID(__spec__));
    if (spec == NULL && _PyErr_Occurred(tstate)) {
        goto error;
    }

    if (package != NULL) {
        Py_INCREF(package);
        if (!PyUnicode_Check(package)) {
            _PyErr_SetString(tstate, PyExc_TypeError,
                             "package must be a string");
            goto error;
        }
        else if (spec != NULL && spec != Py_None) {
            int equal;
            PyObject *parent = PyObject_GetAttr(spec, &_Py_ID(parent));
            if (parent == NULL) {
                goto error;
            }

            equal = PyObject_RichCompareBool(package, parent, Py_EQ);
            Py_DECREF(parent);
            if (equal < 0) {
                goto error;
            }
            else if (equal == 0) {
                if (PyErr_WarnEx(PyExc_DeprecationWarning,
                        "__package__ != __spec__.parent", 1) < 0) {
                    goto error;
                }
            }
        }
    }
    else if (spec != NULL && spec != Py_None) {
        package = PyObject_GetAttr(spec, &_Py_ID(parent));
        if (package == NULL) {
            goto error;
        }
        else if (!PyUnicode_Check(package)) {
            _PyErr_SetString(tstate, PyExc_TypeError,
                             "__spec__.parent must be a string");
            goto error;
        }
    }
    else {
        if (PyErr_WarnEx(PyExc_ImportWarning,
                    "can't resolve package from __spec__ or __package__, "
                    "falling back on __name__ and __path__", 1) < 0) {
            goto error;
        }

        package = PyDict_GetItemWithError(globals, &_Py_ID(__name__));
        if (package == NULL) {
            if (!_PyErr_Occurred(tstate)) {
                _PyErr_SetString(tstate, PyExc_KeyError,
                                 "'__name__' not in globals");
            }
            goto error;
        }

        Py_INCREF(package);
        if (!PyUnicode_Check(package)) {
            _PyErr_SetString(tstate, PyExc_TypeError,
                             "__name__ must be a string");
            goto error;
        }

        int haspath = PyDict_Contains(globals, &_Py_ID(__path__));
        if (haspath < 0) {
            goto error;
        }
        if (!haspath) {
            Py_ssize_t dot;

            if (PyUnicode_READY(package) < 0) {
                goto error;
            }

            dot = PyUnicode_FindChar(package, '.',
                                        0, PyUnicode_GET_LENGTH(package), -1);
            if (dot == -2) {
                goto error;
            }
            else if (dot == -1) {
                goto no_parent_error;
            }
            PyObject *substr = PyUnicode_Substring(package, 0, dot);
            if (substr == NULL) {
                goto error;
            }
            Py_SETREF(package, substr);
        }
    }

    last_dot = PyUnicode_GET_LENGTH(package);
    if (last_dot == 0) {
        goto no_parent_error;
    }

    for (level_up = 1; level_up < level; level_up += 1) {
        last_dot = PyUnicode_FindChar(package, '.', 0, last_dot, -1);
        if (last_dot == -2) {
            goto error;
        }
        else if (last_dot == -1) {
            _PyErr_SetString(tstate, PyExc_ImportError,
                             "attempted relative import beyond top-level "
                             "package");
            goto error;
        }
    }

    base = PyUnicode_Substring(package, 0, last_dot);
    Py_DECREF(package);
    if (base == NULL || PyUnicode_GET_LENGTH(name) == 0) {
        return base;
    }

    abs_name = PyUnicode_FromFormat("%U.%U", base, name);
    Py_DECREF(base);
    return abs_name;

  no_parent_error:
    _PyErr_SetString(tstate, PyExc_ImportError,
                     "attempted relative import "
                     "with no known parent package");

  error:
    Py_XDECREF(package);
    return NULL;
}

static PyObject *
import_find_and_load(PyThreadState *tstate, PyObject *abs_name)
{
    PyObject *mod = NULL;
    PyInterpreterState *interp = tstate->interp;
    int import_time = _PyInterpreterState_GetConfig(interp)->import_time;
#define import_level _PyRuntime.imports.find_and_load.import_level
#define accumulated _PyRuntime.imports.find_and_load.accumulated

    _PyTime_t t1 = 0, accumulated_copy = accumulated;

    PyObject *sys_path = PySys_GetObject("path");
    PyObject *sys_meta_path = PySys_GetObject("meta_path");
    PyObject *sys_path_hooks = PySys_GetObject("path_hooks");
    if (_PySys_Audit(tstate, "import", "OOOOO",
                     abs_name, Py_None, sys_path ? sys_path : Py_None,
                     sys_meta_path ? sys_meta_path : Py_None,
                     sys_path_hooks ? sys_path_hooks : Py_None) < 0) {
        return NULL;
    }


    /* XOptions is initialized after first some imports.
     * So we can't have negative cache before completed initialization.
     * Anyway, importlib._find_and_load is much slower than
     * _PyDict_GetItemIdWithError().
     */
    if (import_time) {
#define header _PyRuntime.imports.find_and_load.header
        if (header) {
            fputs("import time: self [us] | cumulative | imported package\n",
                  stderr);
            header = 0;
        }
#undef header

        import_level++;
        t1 = _PyTime_GetPerfCounter();
        accumulated = 0;
    }

    if (PyDTrace_IMPORT_FIND_LOAD_START_ENABLED())
        PyDTrace_IMPORT_FIND_LOAD_START(PyUnicode_AsUTF8(abs_name));

    mod = PyObject_CallMethodObjArgs(interp->importlib, &_Py_ID(_find_and_load),
                                     abs_name, interp->import_func, NULL);

    if (PyDTrace_IMPORT_FIND_LOAD_DONE_ENABLED())
        PyDTrace_IMPORT_FIND_LOAD_DONE(PyUnicode_AsUTF8(abs_name),
                                       mod != NULL);

    if (import_time) {
        _PyTime_t cum = _PyTime_GetPerfCounter() - t1;

        import_level--;
        fprintf(stderr, "import time: %9ld | %10ld | %*s%s\n",
                (long)_PyTime_AsMicroseconds(cum - accumulated, _PyTime_ROUND_CEILING),
                (long)_PyTime_AsMicroseconds(cum, _PyTime_ROUND_CEILING),
                import_level*2, "", PyUnicode_AsUTF8(abs_name));

        accumulated = accumulated_copy + cum;
    }

    return mod;
#undef import_level
#undef accumulated
}

PyObject *
PyImport_GetModule(PyObject *name)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *mod;

    mod = import_get_module(tstate, name);
    if (mod != NULL && mod != Py_None) {
        if (import_ensure_initialized(tstate->interp, mod, name) < 0) {
            Py_DECREF(mod);
            remove_importlib_frames(tstate);
            return NULL;
        }
    }
    return mod;
}

PyObject *
PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
                                 PyObject *locals, PyObject *fromlist,
                                 int level)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *abs_name = NULL;
    PyObject *final_mod = NULL;
    PyObject *mod = NULL;
    PyObject *package = NULL;
    PyInterpreterState *interp = tstate->interp;
    int has_from;

    if (name == NULL) {
        _PyErr_SetString(tstate, PyExc_ValueError, "Empty module name");
        goto error;
    }

    /* The below code is importlib.__import__() & _gcd_import(), ported to C
       for added performance. */

    if (!PyUnicode_Check(name)) {
        _PyErr_SetString(tstate, PyExc_TypeError,
                         "module name must be a string");
        goto error;
    }
    if (PyUnicode_READY(name) < 0) {
        goto error;
    }
    if (level < 0) {
        _PyErr_SetString(tstate, PyExc_ValueError, "level must be >= 0");
        goto error;
    }

    if (level > 0) {
        abs_name = resolve_name(tstate, name, globals, level);
        if (abs_name == NULL)
            goto error;
    }
    else {  /* level == 0 */
        if (PyUnicode_GET_LENGTH(name) == 0) {
            _PyErr_SetString(tstate, PyExc_ValueError, "Empty module name");
            goto error;
        }
        abs_name = Py_NewRef(name);
    }

    mod = import_get_module(tstate, abs_name);
    if (mod == NULL && _PyErr_Occurred(tstate)) {
        goto error;
    }

    if (mod != NULL && mod != Py_None) {
        if (import_ensure_initialized(tstate->interp, mod, abs_name) < 0) {
            goto error;
        }
    }
    else {
        Py_XDECREF(mod);
        mod = import_find_and_load(tstate, abs_name);
        if (mod == NULL) {
            goto error;
        }
    }

    has_from = 0;
    if (fromlist != NULL && fromlist != Py_None) {
        has_from = PyObject_IsTrue(fromlist);
        if (has_from < 0)
            goto error;
    }
    if (!has_from) {
        Py_ssize_t len = PyUnicode_GET_LENGTH(name);
        if (level == 0 || len > 0) {
            Py_ssize_t dot;

            dot = PyUnicode_FindChar(name, '.', 0, len, 1);
            if (dot == -2) {
                goto error;
            }

            if (dot == -1) {
                /* No dot in module name, simple exit */
                final_mod = Py_NewRef(mod);
                goto error;
            }

            if (level == 0) {
                PyObject *front = PyUnicode_Substring(name, 0, dot);
                if (front == NULL) {
                    goto error;
                }

                final_mod = PyImport_ImportModuleLevelObject(front, NULL, NULL, NULL, 0);
                Py_DECREF(front);
            }
            else {
                Py_ssize_t cut_off = len - dot;
                Py_ssize_t abs_name_len = PyUnicode_GET_LENGTH(abs_name);
                PyObject *to_return = PyUnicode_Substring(abs_name, 0,
                                                        abs_name_len - cut_off);
                if (to_return == NULL) {
                    goto error;
                }

                final_mod = import_get_module(tstate, to_return);
                Py_DECREF(to_return);
                if (final_mod == NULL) {
                    if (!_PyErr_Occurred(tstate)) {
                        _PyErr_Format(tstate, PyExc_KeyError,
                                      "%R not in sys.modules as expected",
                                      to_return);
                    }
                    goto error;
                }
            }
        }
        else {
            final_mod = Py_NewRef(mod);
        }
    }
    else {
        PyObject *path;
        if (_PyObject_LookupAttr(mod, &_Py_ID(__path__), &path) < 0) {
            goto error;
        }
        if (path) {
            Py_DECREF(path);
            final_mod = PyObject_CallMethodObjArgs(
                        interp->importlib, &_Py_ID(_handle_fromlist),
                        mod, fromlist, interp->import_func, NULL);
        }
        else {
            final_mod = Py_NewRef(mod);
        }
    }

  error:
    Py_XDECREF(abs_name);
    Py_XDECREF(mod);
    Py_XDECREF(package);
    if (final_mod == NULL) {
        remove_importlib_frames(tstate);
    }
    return final_mod;
}

PyObject *
PyImport_ImportModuleLevel(const char *name, PyObject *globals, PyObject *locals,
                           PyObject *fromlist, int level)
{
    PyObject *nameobj, *mod;
    nameobj = PyUnicode_FromString(name);
    if (nameobj == NULL)
        return NULL;
    mod = PyImport_ImportModuleLevelObject(nameobj, globals, locals,
                                           fromlist, level);
    Py_DECREF(nameobj);
    return mod;
}


/* Re-import a module of any kind and return its module object, WITH
   INCREMENTED REFERENCE COUNT */

PyObject *
PyImport_ReloadModule(PyObject *m)
{
    PyObject *reloaded_module = NULL;
    PyObject *importlib = PyImport_GetModule(&_Py_ID(importlib));
    if (importlib == NULL) {
        if (PyErr_Occurred()) {
            return NULL;
        }

        importlib = PyImport_ImportModule("importlib");
        if (importlib == NULL) {
            return NULL;
        }
    }

    reloaded_module = PyObject_CallMethodOneArg(importlib, &_Py_ID(reload), m);
    Py_DECREF(importlib);
    return reloaded_module;
}


/* Higher-level import emulator which emulates the "import" statement
   more accurately -- it invokes the __import__() function from the
   builtins of the current globals.  This means that the import is
   done using whatever import hooks are installed in the current
   environment.
   A dummy list ["__doc__"] is passed as the 4th argument so that
   e.g. PyImport_Import(PyUnicode_FromString("win32com.client.gencache"))
   will return <module "gencache"> instead of <module "win32com">. */

PyObject *
PyImport_Import(PyObject *module_name)
{
    PyThreadState *tstate = _PyThreadState_GET();
    PyObject *globals = NULL;
    PyObject *import = NULL;
    PyObject *builtins = NULL;
    PyObject *r = NULL;

    PyObject *from_list = PyList_New(0);
    if (from_list == NULL) {
        goto err;
    }

    /* Get the builtins from current globals */
    globals = PyEval_GetGlobals();
    if (globals != NULL) {
        Py_INCREF(globals);
        builtins = PyObject_GetItem(globals, &_Py_ID(__builtins__));
        if (builtins == NULL)
            goto err;
    }
    else {
        /* No globals -- use standard builtins, and fake globals */
        builtins = PyImport_ImportModuleLevel("builtins",
                                              NULL, NULL, NULL, 0);
        if (builtins == NULL) {
            goto err;
        }
        globals = Py_BuildValue("{OO}", &_Py_ID(__builtins__), builtins);
        if (globals == NULL)
            goto err;
    }

    /* Get the __import__ function from the builtins */
    if (PyDict_Check(builtins)) {
        import = PyObject_GetItem(builtins, &_Py_ID(__import__));
        if (import == NULL) {
            _PyErr_SetObject(tstate, PyExc_KeyError, &_Py_ID(__import__));
        }
    }
    else
        import = PyObject_GetAttr(builtins, &_Py_ID(__import__));
    if (import == NULL)
        goto err;

    /* Call the __import__ function with the proper argument list
       Always use absolute import here.
       Calling for side-effect of import. */
    r = PyObject_CallFunction(import, "OOOOi", module_name, globals,
                              globals, from_list, 0, NULL);
    if (r == NULL)
        goto err;
    Py_DECREF(r);

    r = import_get_module(tstate, module_name);
    if (r == NULL && !_PyErr_Occurred(tstate)) {
        _PyErr_SetObject(tstate, PyExc_KeyError, module_name);
    }

  err:
    Py_XDECREF(globals);
    Py_XDECREF(builtins);
    Py_XDECREF(import);
    Py_XDECREF(from_list);

    return r;
}

/*[clinic input]
_imp.extension_suffixes

Returns the list of file suffixes used to identify extension modules.
[clinic start generated code]*/

static PyObject *
_imp_extension_suffixes_impl(PyObject *module)
/*[clinic end generated code: output=0bf346e25a8f0cd3 input=ecdeeecfcb6f839e]*/
{
    PyObject *list;

    list = PyList_New(0);
    if (list == NULL)
        return NULL;
#ifdef HAVE_DYNAMIC_LOADING
    const char *suffix;
    unsigned int index = 0;

    while ((suffix = _PyImport_DynLoadFiletab[index])) {
        PyObject *item = PyUnicode_FromString(suffix);
        if (item == NULL) {
            Py_DECREF(list);
            return NULL;
        }
        if (PyList_Append(list, item) < 0) {
            Py_DECREF(list);
            Py_DECREF(item);
            return NULL;
        }
        Py_DECREF(item);
        index += 1;
    }
#endif
    return list;
}

/*[clinic input]
_imp.init_frozen

    name: unicode
    /

Initializes a frozen module.
[clinic start generated code]*/

static PyObject *
_imp_init_frozen_impl(PyObject *module, PyObject *name)
/*[clinic end generated code: output=fc0511ed869fd69c input=13019adfc04f3fb3]*/
{
    PyThreadState *tstate = _PyThreadState_GET();
    int ret;

    ret = PyImport_ImportFrozenModuleObject(name);
    if (ret < 0)
        return NULL;
    if (ret == 0) {
        Py_RETURN_NONE;
    }
    return import_add_module(tstate, name);
}

/*[clinic input]
_imp.find_frozen

    name: unicode
    /
    *
    withdata: bool = False

Return info about the corresponding frozen module (if there is one) or None.

The returned info (a 2-tuple):

 * data         the raw marshalled bytes
 * is_package   whether or not it is a package
 * origname     the originally frozen module's name, or None if not
                a stdlib module (this will usually be the same as
                the module's current name)
[clinic start generated code]*/

static PyObject *
_imp_find_frozen_impl(PyObject *module, PyObject *name, int withdata)
/*[clinic end generated code: output=8c1c3c7f925397a5 input=22a8847c201542fd]*/
{
    struct frozen_info info;
    frozen_status status = find_frozen(name, &info);
    if (status == FROZEN_NOT_FOUND || status == FROZEN_DISABLED) {
        Py_RETURN_NONE;
    }
    else if (status == FROZEN_BAD_NAME) {
        Py_RETURN_NONE;
    }
    else if (status != FROZEN_OKAY) {
        set_frozen_error(status, name);
        return NULL;
    }

    PyObject *data = NULL;
    if (withdata) {
        data = PyMemoryView_FromMemory((char *)info.data, info.size, PyBUF_READ);
        if (data == NULL) {
            return NULL;
        }
    }

    PyObject *origname = NULL;
    if (info.origname != NULL && info.origname[0] != '\0') {
        origname = PyUnicode_FromString(info.origname);
        if (origname == NULL) {
            Py_DECREF(data);
            return NULL;
        }
    }

    PyObject *result = PyTuple_Pack(3, data ? data : Py_None,
                                    info.is_package ? Py_True : Py_False,
                                    origname ? origname : Py_None);
    Py_XDECREF(origname);
    Py_XDECREF(data);
    return result;
}

/*[clinic input]
_imp.get_frozen_object

    name: unicode
    data as dataobj: object = None
    /

Create a code object for a frozen module.
[clinic start generated code]*/

static PyObject *
_imp_get_frozen_object_impl(PyObject *module, PyObject *name,
                            PyObject *dataobj)
/*[clinic end generated code: output=54368a673a35e745 input=034bdb88f6460b7b]*/
{
    struct frozen_info info = {0};
    Py_buffer buf = {0};
    if (PyObject_CheckBuffer(dataobj)) {
        if (PyObject_GetBuffer(dataobj, &buf, PyBUF_READ) != 0) {
            return NULL;
        }
        info.data = (const char *)buf.buf;
        info.size = buf.len;
    }
    else if (dataobj != Py_None) {
        _PyArg_BadArgument("get_frozen_object", "argument 2", "bytes", dataobj);
        return NULL;
    }
    else {
        frozen_status status = find_frozen(name, &info);
        if (status != FROZEN_OKAY) {
            set_frozen_error(status, name);
            return NULL;
        }
    }

    if (info.nameobj == NULL) {
        info.nameobj = name;
    }
    if (info.size == 0 && info.get_code == NULL) {
        /* Does not contain executable code. */
        set_frozen_error(FROZEN_INVALID, name);
        return NULL;
    }

    PyObject *codeobj = unmarshal_frozen_code(&info);
    if (dataobj != Py_None) {
        PyBuffer_Release(&buf);
    }
    return codeobj;
}

/*[clinic input]
_imp.is_frozen_package

    name: unicode
    /

Returns True if the module name is of a frozen package.
[clinic start generated code]*/

static PyObject *
_imp_is_frozen_package_impl(PyObject *module, PyObject *name)
/*[clinic end generated code: output=e70cbdb45784a1c9 input=81b6cdecd080fbb8]*/
{
    struct frozen_info info;
    frozen_status status = find_frozen(name, &info);
    if (status != FROZEN_OKAY && status != FROZEN_EXCLUDED) {
        set_frozen_error(status, name);
        return NULL;
    }
    return PyBool_FromLong(info.is_package);
}

/*[clinic input]
_imp.is_builtin

    name: unicode
    /

Returns True if the module name corresponds to a built-in module.
[clinic start generated code]*/

static PyObject *
_imp_is_builtin_impl(PyObject *module, PyObject *name)
/*[clinic end generated code: output=3bfd1162e2d3be82 input=86befdac021dd1c7]*/
{
    return PyLong_FromLong(is_builtin(name));
}

/*[clinic input]
_imp.is_frozen

    name: unicode
    /

Returns True if the module name corresponds to a frozen module.
[clinic start generated code]*/

static PyObject *
_imp_is_frozen_impl(PyObject *module, PyObject *name)
/*[clinic end generated code: output=01f408f5ec0f2577 input=7301dbca1897d66b]*/
{
    struct frozen_info info;
    frozen_status status = find_frozen(name, &info);
    if (status != FROZEN_OKAY) {
        Py_RETURN_FALSE;
    }
    Py_RETURN_TRUE;
}

/*[clinic input]
_imp._frozen_module_names

Returns the list of available frozen modules.
[clinic start generated code]*/

static PyObject *
_imp__frozen_module_names_impl(PyObject *module)
/*[clinic end generated code: output=80609ef6256310a8 input=76237fbfa94460d2]*/
{
    return list_frozen_module_names();
}

/*[clinic input]
_imp._override_frozen_modules_for_tests

    override: int
    /

(internal-only) Override PyConfig.use_frozen_modules.

(-1: "off", 1: "on", 0: no override)
See frozen_modules() in Lib/test/support/import_helper.py.
[clinic start generated code]*/

static PyObject *
_imp__override_frozen_modules_for_tests_impl(PyObject *module, int override)
/*[clinic end generated code: output=36d5cb1594160811 input=8f1f95a3ef21aec3]*/
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    interp->override_frozen_modules = override;
    Py_RETURN_NONE;
}

/* Common implementation for _imp.exec_dynamic and _imp.exec_builtin */
static int
exec_builtin_or_dynamic(PyObject *mod) {
    PyModuleDef *def;
    void *state;

    if (!PyModule_Check(mod)) {
        return 0;
    }

    def = PyModule_GetDef(mod);
    if (def == NULL) {
        return 0;
    }

    state = PyModule_GetState(mod);
    if (state) {
        /* Already initialized; skip reload */
        return 0;
    }

    return PyModule_ExecDef(mod, def);
}

#ifdef HAVE_DYNAMIC_LOADING

/*[clinic input]
_imp.create_dynamic

    spec: object
    file: object = NULL
    /

Create an extension module.
[clinic start generated code]*/

static PyObject *
_imp_create_dynamic_impl(PyObject *module, PyObject *spec, PyObject *file)
/*[clinic end generated code: output=83249b827a4fde77 input=c31b954f4cf4e09d]*/
{
    PyObject *mod, *name, *path;
    FILE *fp;

    name = PyObject_GetAttrString(spec, "name");
    if (name == NULL) {
        return NULL;
    }

    path = PyObject_GetAttrString(spec, "origin");
    if (path == NULL) {
        Py_DECREF(name);
        return NULL;
    }

    PyThreadState *tstate = _PyThreadState_GET();
    mod = import_find_extension(tstate, name, path);
    if (mod != NULL || PyErr_Occurred()) {
        Py_DECREF(name);
        Py_DECREF(path);
        return mod;
    }

    if (file != NULL) {
        fp = _Py_fopen_obj(path, "r");
        if (fp == NULL) {
            Py_DECREF(name);
            Py_DECREF(path);
            return NULL;
        }
    }
    else
        fp = NULL;

    mod = _PyImport_LoadDynamicModuleWithSpec(spec, fp);

    Py_DECREF(name);
    Py_DECREF(path);
    if (fp)
        fclose(fp);
    return mod;
}

/*[clinic input]
_imp.exec_dynamic -> int

    mod: object
    /

Initialize an extension module.
[clinic start generated code]*/

static int
_imp_exec_dynamic_impl(PyObject *module, PyObject *mod)
/*[clinic end generated code: output=f5720ac7b465877d input=9fdbfcb250280d3a]*/
{
    return exec_builtin_or_dynamic(mod);
}


#endif /* HAVE_DYNAMIC_LOADING */

/*[clinic input]
_imp.exec_builtin -> int

    mod: object
    /

Initialize a built-in module.
[clinic start generated code]*/

static int
_imp_exec_builtin_impl(PyObject *module, PyObject *mod)
/*[clinic end generated code: output=0262447b240c038e input=7beed5a2f12a60ca]*/
{
    return exec_builtin_or_dynamic(mod);
}

/*[clinic input]
_imp.source_hash

    key: long
    source: Py_buffer
[clinic start generated code]*/

static PyObject *
_imp_source_hash_impl(PyObject *module, long key, Py_buffer *source)
/*[clinic end generated code: output=edb292448cf399ea input=9aaad1e590089789]*/
{
    union {
        uint64_t x;
        char data[sizeof(uint64_t)];
    } hash;
    hash.x = _Py_KeyedHash((uint64_t)key, source->buf, source->len);
#if !PY_LITTLE_ENDIAN
    // Force to little-endian. There really ought to be a succinct standard way
    // to do this.
    for (size_t i = 0; i < sizeof(hash.data)/2; i++) {
        char tmp = hash.data[i];
        hash.data[i] = hash.data[sizeof(hash.data) - i - 1];
        hash.data[sizeof(hash.data) - i - 1] = tmp;
    }
#endif
    return PyBytes_FromStringAndSize(hash.data, sizeof(hash.data));
}


PyDoc_STRVAR(doc_imp,
"(Extremely) low-level import machinery bits as used by importlib and imp.");

static PyMethodDef imp_methods[] = {
    _IMP_EXTENSION_SUFFIXES_METHODDEF
    _IMP_LOCK_HELD_METHODDEF
    _IMP_ACQUIRE_LOCK_METHODDEF
    _IMP_RELEASE_LOCK_METHODDEF
    _IMP_FIND_FROZEN_METHODDEF
    _IMP_GET_FROZEN_OBJECT_METHODDEF
    _IMP_IS_FROZEN_PACKAGE_METHODDEF
    _IMP_CREATE_BUILTIN_METHODDEF
    _IMP_INIT_FROZEN_METHODDEF
    _IMP_IS_BUILTIN_METHODDEF
    _IMP_IS_FROZEN_METHODDEF
    _IMP__FROZEN_MODULE_NAMES_METHODDEF
    _IMP__OVERRIDE_FROZEN_MODULES_FOR_TESTS_METHODDEF
    _IMP_CREATE_DYNAMIC_METHODDEF
    _IMP_EXEC_DYNAMIC_METHODDEF
    _IMP_EXEC_BUILTIN_METHODDEF
    _IMP__FIX_CO_FILENAME_METHODDEF
    _IMP_SOURCE_HASH_METHODDEF
    {NULL, NULL}  /* sentinel */
};


static int
imp_module_exec(PyObject *module)
{
    const wchar_t *mode = _Py_GetConfig()->check_hash_pycs_mode;
    PyObject *pyc_mode = PyUnicode_FromWideChar(mode, -1);
    if (pyc_mode == NULL) {
        return -1;
    }
    if (PyModule_AddObjectRef(module, "check_hash_based_pycs", pyc_mode) < 0) {
        Py_DECREF(pyc_mode);
        return -1;
    }
    Py_DECREF(pyc_mode);

    return 0;
}


static PyModuleDef_Slot imp_slots[] = {
    {Py_mod_exec, imp_module_exec},
    {0, NULL}
};

static struct PyModuleDef imp_module = {
    PyModuleDef_HEAD_INIT,
    .m_name = "_imp",
    .m_doc = doc_imp,
    .m_size = 0,
    .m_methods = imp_methods,
    .m_slots = imp_slots,
};

PyMODINIT_FUNC
PyInit__imp(void)
{
    return PyModuleDef_Init(&imp_module);
}


// Import the _imp extension by calling manually _imp.create_builtin() and
// _imp.exec_builtin() since importlib is not initialized yet. Initializing
// importlib requires the _imp module: this function fix the bootstrap issue.
PyObject*
_PyImport_BootstrapImp(PyThreadState *tstate)
{
    PyObject *name = PyUnicode_FromString("_imp");
    if (name == NULL) {
        return NULL;
    }

    // Mock a ModuleSpec object just good enough for PyModule_FromDefAndSpec():
    // an object with just a name attribute.
    //
    // _imp.__spec__ is overridden by importlib._bootstrap._instal() anyway.
    PyObject *attrs = Py_BuildValue("{sO}", "name", name);
    if (attrs == NULL) {
        goto error;
    }
    PyObject *spec = _PyNamespace_New(attrs);
    Py_DECREF(attrs);
    if (spec == NULL) {
        goto error;
    }

    // Create the _imp module from its definition.
    PyObject *mod = create_builtin(tstate, name, spec);
    Py_CLEAR(name);
    Py_DECREF(spec);
    if (mod == NULL) {
        goto error;
    }
    assert(mod != Py_None);  // not found

    // Execute the _imp module: call imp_module_exec().
    if (exec_builtin_or_dynamic(mod) < 0) {
        Py_DECREF(mod);
        goto error;
    }
    return mod;

error:
    Py_XDECREF(name);
    return NULL;
}


/* API for embedding applications that want to add their own entries
   to the table of built-in modules.  This should normally be called
   *before* Py_Initialize().  When the table resize fails, -1 is
   returned and the existing table is unchanged.

   After a similar function by Just van Rossum. */

int
PyImport_ExtendInittab(struct _inittab *newtab)
{
    struct _inittab *p;
    size_t i, n;
    int res = 0;

    if (_PyRuntime.imports.inittab != NULL) {
        Py_FatalError("PyImport_ExtendInittab() may be be called after Py_Initialize()");
    }

    /* Count the number of entries in both tables */
    for (n = 0; newtab[n].name != NULL; n++)
        ;
    if (n == 0)
        return 0; /* Nothing to do */
    for (i = 0; PyImport_Inittab[i].name != NULL; i++)
        ;

    /* Force default raw memory allocator to get a known allocator to be able
       to release the memory in _PyImport_Fini2() */
    PyMemAllocatorEx old_alloc;
    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);

    /* Allocate new memory for the combined table */
    p = NULL;
    if (i + n <= SIZE_MAX / sizeof(struct _inittab) - 1) {
        size_t size = sizeof(struct _inittab) * (i + n + 1);
        p = PyMem_RawRealloc(inittab_copy, size);
    }
    if (p == NULL) {
        res = -1;
        goto done;
    }

    /* Copy the tables into the new memory at the first call
       to PyImport_ExtendInittab(). */
    if (inittab_copy != PyImport_Inittab) {
        memcpy(p, PyImport_Inittab, (i+1) * sizeof(struct _inittab));
    }
    memcpy(p + i, newtab, (n + 1) * sizeof(struct _inittab));
    PyImport_Inittab = inittab_copy = p;

done:
    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
    return res;
}

/* Shorthand to add a single entry given a name and a function */

int
PyImport_AppendInittab(const char *name, PyObject* (*initfunc)(void))
{
    struct _inittab newtab[2];

    if (_PyRuntime.imports.inittab != NULL) {
        Py_FatalError("PyImport_AppendInittab() may be be called after Py_Initialize()");
    }

    memset(newtab, '\0', sizeof newtab);

    newtab[0].name = name;
    newtab[0].initfunc = initfunc;

    return PyImport_ExtendInittab(newtab);
}


PyObject *
_PyImport_GetModuleAttr(PyObject *modname, PyObject *attrname)
{
    PyObject *mod = PyImport_Import(modname);
    if (mod == NULL) {
        return NULL;
    }
    PyObject *result = PyObject_GetAttr(mod, attrname);
    Py_DECREF(mod);
    return result;
}

PyObject *
_PyImport_GetModuleAttrString(const char *modname, const char *attrname)
{
    PyObject *pmodname = PyUnicode_FromString(modname);
    if (pmodname == NULL) {
        return NULL;
    }
    PyObject *pattrname = PyUnicode_FromString(attrname);
    if (pattrname == NULL) {
        Py_DECREF(pmodname);
        return NULL;
    }
    PyObject *result = _PyImport_GetModuleAttr(pmodname, pattrname);
    Py_DECREF(pattrname);
    Py_DECREF(pmodname);
    return result;
}

#ifdef __cplusplus
}
#endif