import.c

/* Module definition and import implementation */

#include "Python.h"

#include "Python-ast.h"
#undef Yield /* undefine macro conflicting with winbase.h */
#include "errcode.h"
#include "marshal.h"
#include "code.h"
#include "osdefs.h"
#include "importdl.h"

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

#ifdef MS_WINDOWS
/* for stat.st_mode */
typedef unsigned short mode_t;
/* for _mkdir */
#include <direct.h>
#endif


/* Magic word to reject .pyc files generated by other Python versions.
   It should change for each incompatible change to the bytecode.

   The value of CR and LF is incorporated so if you ever read or write
   a .pyc file in text mode the magic number will be wrong; also, the
   Apple MPW compiler swaps their values, botching string constants.

   The magic numbers must be spaced apart at least 2 values, as the
   -U interpeter flag will cause MAGIC+1 being used. They have been
   odd numbers for some time now.

   There were a variety of old schemes for setting the magic number.
   The current working scheme is to increment the previous value by
   10.

   Starting with the adoption of PEP 3147 in Python 3.2, every bump in magic
   number also includes a new "magic tag", i.e. a human readable string used
   to represent the magic number in __pycache__ directories.  When you change
   the magic number, you must also set a new unique magic tag.  Generally this
   can be named after the Python major version of the magic number bump, but
   it can really be anything, as long as it's different than anything else
   that's come before.  The tags are included in the following table, starting
   with Python 3.2a0.

   Known values:
       Python 1.5:   20121
       Python 1.5.1: 20121
       Python 1.5.2: 20121
       Python 1.6:   50428
       Python 2.0:   50823
       Python 2.0.1: 50823
       Python 2.1:   60202
       Python 2.1.1: 60202
       Python 2.1.2: 60202
       Python 2.2:   60717
       Python 2.3a0: 62011
       Python 2.3a0: 62021
       Python 2.3a0: 62011 (!)
       Python 2.4a0: 62041
       Python 2.4a3: 62051
       Python 2.4b1: 62061
       Python 2.5a0: 62071
       Python 2.5a0: 62081 (ast-branch)
       Python 2.5a0: 62091 (with)
       Python 2.5a0: 62092 (changed WITH_CLEANUP opcode)
       Python 2.5b3: 62101 (fix wrong code: for x, in ...)
       Python 2.5b3: 62111 (fix wrong code: x += yield)
       Python 2.5c1: 62121 (fix wrong lnotab with for loops and
                            storing constants that should have been removed)
       Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp)
       Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode)
       Python 2.6a1: 62161 (WITH_CLEANUP optimization)
       Python 3000:   3000
                      3010 (removed UNARY_CONVERT)
                      3020 (added BUILD_SET)
                      3030 (added keyword-only parameters)
                      3040 (added signature annotations)
                      3050 (print becomes a function)
                      3060 (PEP 3115 metaclass syntax)
                      3061 (string literals become unicode)
                      3071 (PEP 3109 raise changes)
                      3081 (PEP 3137 make __file__ and __name__ unicode)
                      3091 (kill str8 interning)
                      3101 (merge from 2.6a0, see 62151)
                      3103 (__file__ points to source file)
       Python 3.0a4: 3111 (WITH_CLEANUP optimization).
       Python 3.0a5: 3131 (lexical exception stacking, including POP_EXCEPT)
       Python 3.1a0: 3141 (optimize list, set and dict comprehensions:
               change LIST_APPEND and SET_ADD, add MAP_ADD)
       Python 3.1a0: 3151 (optimize conditional branches:
               introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
       Python 3.2a0: 3160 (add SETUP_WITH)
                     tag: cpython-32
       Python 3.2a1: 3170 (add DUP_TOP_TWO, remove DUP_TOPX and ROT_FOUR)
                     tag: cpython-32
       Python 3.2a2  3180 (add DELETE_DEREF)
*/

/* MAGIC must change whenever the bytecode emitted by the compiler may no
   longer be understood by older implementations of the eval loop (usually
   due to the addition of new opcodes)
   TAG must change for each major Python release. The magic number will take
   care of any bytecode changes that occur during development.
*/
#define MAGIC (3180 | ((long)'\r'<<16) | ((long)'\n'<<24))
#define TAG "cpython-32"
#define CACHEDIR "__pycache__"
/* Current magic word and string tag as globals. */
static long pyc_magic = MAGIC;
static const char *pyc_tag = TAG;

/* See _PyImport_FixupExtensionUnicode() below */
static PyObject *extensions = NULL;

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

/* Method from Parser/tokenizer.c */
extern char * PyTokenizer_FindEncoding(int);

struct _inittab *PyImport_Inittab = _PyImport_Inittab;

/* these tables define the module suffixes that Python recognizes */
struct filedescr * _PyImport_Filetab = NULL;

static const struct filedescr _PyImport_StandardFiletab[] = {
    {".py", "U", PY_SOURCE},
#ifdef MS_WINDOWS
    {".pyw", "U", PY_SOURCE},
#endif
    {".pyc", "rb", PY_COMPILED},
    {0, 0}
};


/* Initialize things */

void
_PyImport_Init(void)
{
    const struct filedescr *scan;
    struct filedescr *filetab;
    int countD = 0;
    int countS = 0;

    /* prepare _PyImport_Filetab: copy entries from
       _PyImport_DynLoadFiletab and _PyImport_StandardFiletab.
     */
#ifdef HAVE_DYNAMIC_LOADING
    for (scan = _PyImport_DynLoadFiletab; scan->suffix != NULL; ++scan)
        ++countD;
#endif
    for (scan = _PyImport_StandardFiletab; scan->suffix != NULL; ++scan)
        ++countS;
    filetab = PyMem_NEW(struct filedescr, countD + countS + 1);
    if (filetab == NULL)
        Py_FatalError("Can't initialize import file table.");
#ifdef HAVE_DYNAMIC_LOADING
    memcpy(filetab, _PyImport_DynLoadFiletab,
           countD * sizeof(struct filedescr));
#endif
    memcpy(filetab + countD, _PyImport_StandardFiletab,
           countS * sizeof(struct filedescr));
    filetab[countD + countS].suffix = NULL;

    _PyImport_Filetab = filetab;

    if (Py_OptimizeFlag) {
        /* Replace ".pyc" with ".pyo" in _PyImport_Filetab */
        for (; filetab->suffix != NULL; filetab++) {
            if (strcmp(filetab->suffix, ".pyc") == 0)
                filetab->suffix = ".pyo";
        }
    }
}

void
_PyImportHooks_Init(void)
{
    PyObject *v, *path_hooks = NULL, *zimpimport;
    int err = 0;

    /* adding sys.path_hooks and sys.path_importer_cache, setting up
       zipimport */
    if (PyType_Ready(&PyNullImporter_Type) < 0)
        goto error;

    if (Py_VerboseFlag)
        PySys_WriteStderr("# installing zipimport hook\n");

    v = PyList_New(0);
    if (v == NULL)
        goto error;
    err = PySys_SetObject("meta_path", v);
    Py_DECREF(v);
    if (err)
        goto error;
    v = PyDict_New();
    if (v == NULL)
        goto error;
    err = PySys_SetObject("path_importer_cache", v);
    Py_DECREF(v);
    if (err)
        goto error;
    path_hooks = PyList_New(0);
    if (path_hooks == NULL)
        goto error;
    err = PySys_SetObject("path_hooks", path_hooks);
    if (err) {
  error:
        PyErr_Print();
        Py_FatalError("initializing sys.meta_path, sys.path_hooks, "
                      "path_importer_cache, or NullImporter failed"
                      );
    }

    zimpimport = PyImport_ImportModule("zipimport");
    if (zimpimport == NULL) {
        PyErr_Clear(); /* No zip import module -- okay */
        if (Py_VerboseFlag)
            PySys_WriteStderr("# can't import zipimport\n");
    }
    else {
        PyObject *zipimporter = PyObject_GetAttrString(zimpimport,
                                                       "zipimporter");
        Py_DECREF(zimpimport);
        if (zipimporter == NULL) {
            PyErr_Clear(); /* No zipimporter object -- okay */
            if (Py_VerboseFlag)
                PySys_WriteStderr(
                    "# can't import zipimport.zipimporter\n");
        }
        else {
            /* sys.path_hooks.append(zipimporter) */
            err = PyList_Append(path_hooks, zipimporter);
            Py_DECREF(zipimporter);
            if (err)
                goto error;
            if (Py_VerboseFlag)
                PySys_WriteStderr(
                    "# installed zipimport hook\n");
        }
    }
    Py_DECREF(path_hooks);
}

/* 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. */

#ifdef WITH_THREAD

#include "pythread.h"

static PyThread_type_lock import_lock = 0;
static long import_lock_thread = -1;
static int import_lock_level = 0;

void
_PyImport_AcquireLock(void)
{
    long me = PyThread_get_thread_ident();
    if (me == -1)
        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 != -1 || !PyThread_acquire_lock(import_lock, 0))
    {
        PyThreadState *tstate = PyEval_SaveThread();
        PyThread_acquire_lock(import_lock, 1);
        PyEval_RestoreThread(tstate);
    }
    import_lock_thread = me;
    import_lock_level = 1;
}

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

/* This function is called from PyOS_AfterFork 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. */

void
_PyImport_ReInitLock(void)
{
    if (import_lock != NULL)
        import_lock = PyThread_allocate_lock();
    if (import_lock_level > 1) {
        /* Forked as a side effect of import */
        long me = PyThread_get_thread_ident();
        PyThread_acquire_lock(import_lock, 0);
	/* XXX: can the previous line fail? */
        import_lock_thread = me;
        import_lock_level--;
    } else {
        import_lock_thread = -1;
        import_lock_level = 0;
    }
}

#endif

static PyObject *
imp_lock_held(PyObject *self, PyObject *noargs)
{
#ifdef WITH_THREAD
    return PyBool_FromLong(import_lock_thread != -1);
#else
    return PyBool_FromLong(0);
#endif
}

static PyObject *
imp_acquire_lock(PyObject *self, PyObject *noargs)
{
#ifdef WITH_THREAD
    _PyImport_AcquireLock();
#endif
    Py_INCREF(Py_None);
    return Py_None;
}

static PyObject *
imp_release_lock(PyObject *self, PyObject *noargs)
{
#ifdef WITH_THREAD
    if (_PyImport_ReleaseLock() < 0) {
        PyErr_SetString(PyExc_RuntimeError,
                        "not holding the import lock");
        return NULL;
    }
#endif
    Py_INCREF(Py_None);
    return Py_None;
}

void
_PyImport_Fini(void)
{
    Py_XDECREF(extensions);
    extensions = NULL;
    PyMem_DEL(_PyImport_Filetab);
    _PyImport_Filetab = NULL;
#ifdef WITH_THREAD
    if (import_lock != NULL) {
        PyThread_free_lock(import_lock);
        import_lock = NULL;
    }
#endif
}

static void
imp_modules_reloading_clear(void)
{
    PyInterpreterState *interp = PyThreadState_Get()->interp;
    if (interp->modules_reloading != NULL)
        PyDict_Clear(interp->modules_reloading);
}

/* Helper for sys */

PyObject *
PyImport_GetModuleDict(void)
{
    PyInterpreterState *interp = PyThreadState_GET()->interp;
    if (interp->modules == NULL)
        Py_FatalError("PyImport_GetModuleDict: no module dictionary!");
    return interp->modules;
}


/* List of names to clear in sys */
static char* sys_deletes[] = {
    "path", "argv", "ps1", "ps2",
    "last_type", "last_value", "last_traceback",
    "path_hooks", "path_importer_cache", "meta_path",
    /* misc stuff */
    "flags", "float_info",
    NULL
};

static char* sys_files[] = {
    "stdin", "__stdin__",
    "stdout", "__stdout__",
    "stderr", "__stderr__",
    NULL
};


/* Un-initialize things, as good as we can */

void
PyImport_Cleanup(void)
{
    Py_ssize_t pos, ndone;
    char *name;
    PyObject *key, *value, *dict;
    PyInterpreterState *interp = PyThreadState_GET()->interp;
    PyObject *modules = interp->modules;

    if (modules == NULL)
        return; /* Already done */

    /* Delete some special variables first.  These are common
       places where user values hide and people complain when their
       destructors fail.  Since the modules containing them are
       deleted *last* of all, they would come too late in the normal
       destruction order.  Sigh. */

    value = PyDict_GetItemString(modules, "builtins");
    if (value != NULL && PyModule_Check(value)) {
        dict = PyModule_GetDict(value);
        if (Py_VerboseFlag)
            PySys_WriteStderr("# clear builtins._\n");
        PyDict_SetItemString(dict, "_", Py_None);
    }
    value = PyDict_GetItemString(modules, "sys");
    if (value != NULL && PyModule_Check(value)) {
        char **p;
        PyObject *v;
        dict = PyModule_GetDict(value);
        for (p = sys_deletes; *p != NULL; p++) {
            if (Py_VerboseFlag)
                PySys_WriteStderr("# clear sys.%s\n", *p);
            PyDict_SetItemString(dict, *p, Py_None);
        }
        for (p = sys_files; *p != NULL; p+=2) {
            if (Py_VerboseFlag)
                PySys_WriteStderr("# restore sys.%s\n", *p);
            v = PyDict_GetItemString(dict, *(p+1));
            if (v == NULL)
                v = Py_None;
            PyDict_SetItemString(dict, *p, v);
        }
    }

    /* First, delete __main__ */
    value = PyDict_GetItemString(modules, "__main__");
    if (value != NULL && PyModule_Check(value)) {
        if (Py_VerboseFlag)
            PySys_WriteStderr("# cleanup __main__\n");
        _PyModule_Clear(value);
        PyDict_SetItemString(modules, "__main__", Py_None);
    }

    /* The special treatment of "builtins" here is because even
       when it's not referenced as a module, its dictionary is
       referenced by almost every module's __builtins__.  Since
       deleting a module clears its dictionary (even if there are
       references left to it), we need to delete the "builtins"
       module last.  Likewise, we don't delete sys until the very
       end because it is implicitly referenced (e.g. by print).

       Also note that we 'delete' modules by replacing their entry
       in the modules dict with None, rather than really deleting
       them; this avoids a rehash of the modules dictionary and
       also marks them as "non existent" so they won't be
       re-imported. */

    /* Next, repeatedly delete modules with a reference count of
       one (skipping builtins and sys) and delete them */
    do {
        ndone = 0;
        pos = 0;
        while (PyDict_Next(modules, &pos, &key, &value)) {
            if (value->ob_refcnt != 1)
                continue;
            if (PyUnicode_Check(key) && PyModule_Check(value)) {
                name = _PyUnicode_AsString(key);
                if (strcmp(name, "builtins") == 0)
                    continue;
                if (strcmp(name, "sys") == 0)
                    continue;
                if (Py_VerboseFlag)
                    PySys_WriteStderr(
                        "# cleanup[1] %s\n", name);
                _PyModule_Clear(value);
                PyDict_SetItem(modules, key, Py_None);
                ndone++;
            }
        }
    } while (ndone > 0);

    /* Next, delete all modules (still skipping builtins and sys) */
    pos = 0;
    while (PyDict_Next(modules, &pos, &key, &value)) {
        if (PyUnicode_Check(key) && PyModule_Check(value)) {
            name = _PyUnicode_AsString(key);
            if (strcmp(name, "builtins") == 0)
                continue;
            if (strcmp(name, "sys") == 0)
                continue;
            if (Py_VerboseFlag)
                PySys_WriteStderr("# cleanup[2] %s\n", name);
            _PyModule_Clear(value);
            PyDict_SetItem(modules, key, Py_None);
        }
    }

    /* Next, delete sys and builtins (in that order) */
    value = PyDict_GetItemString(modules, "sys");
    if (value != NULL && PyModule_Check(value)) {
        if (Py_VerboseFlag)
            PySys_WriteStderr("# cleanup sys\n");
        _PyModule_Clear(value);
        PyDict_SetItemString(modules, "sys", Py_None);
    }
    value = PyDict_GetItemString(modules, "builtins");
    if (value != NULL && PyModule_Check(value)) {
        if (Py_VerboseFlag)
            PySys_WriteStderr("# cleanup builtins\n");
        _PyModule_Clear(value);
        PyDict_SetItemString(modules, "builtins", Py_None);
    }

    /* Finally, clear and delete the modules directory */
    PyDict_Clear(modules);
    interp->modules = NULL;
    Py_DECREF(modules);
    Py_CLEAR(interp->modules_reloading);
}


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

long
PyImport_GetMagicNumber(void)
{
    return pyc_magic;
}


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

/* 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 module name
   (for built-in modules) or by filename (for dynamically loaded
   modules), containing these modules.  A copy of the module's
   dictionary is stored by calling _PyImport_FixupExtensionUnicode()
   immediately after the module initialization function succeeds.  A
   copy can be retrieved from there by calling
   _PyImport_FindExtensionUnicode().

   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.
*/

int
_PyImport_FixupExtensionUnicode(PyObject *mod, char *name, PyObject *filename)
{
    PyObject *modules, *dict;
    struct PyModuleDef *def;
    if (extensions == NULL) {
        extensions = PyDict_New();
        if (extensions == NULL)
            return -1;
    }
    if (mod == NULL || !PyModule_Check(mod)) {
        PyErr_BadInternalCall();
        return -1;
    }
    def = PyModule_GetDef(mod);
    if (!def) {
        PyErr_BadInternalCall();
        return -1;
    }
    modules = PyImport_GetModuleDict();
    if (PyDict_SetItemString(modules, name, mod) < 0)
        return -1;
    if (_PyState_AddModule(mod, def) < 0) {
        PyDict_DelItemString(modules, name);
        return -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_DECREF(def->m_base.m_copy);
            def->m_base.m_copy = NULL;
        }
        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;
    }
    PyDict_SetItem(extensions, filename, (PyObject*)def);
    return 0;
}

int
_PyImport_FixupBuiltin(PyObject *mod, char *name)
{
    int res;
    PyObject *filename;
    filename = PyUnicode_FromString(name);
    if (filename == NULL)
        return -1;
    res = _PyImport_FixupExtensionUnicode(mod, name, filename);
    Py_DECREF(filename);
    return res;
}

PyObject *
_PyImport_FindExtensionUnicode(char *name, PyObject *filename)
{
    PyObject *mod, *mdict;
    PyModuleDef* def;
    if (extensions == NULL)
        return NULL;
    def = (PyModuleDef*)PyDict_GetItem(extensions, filename);
    if (def == NULL)
        return NULL;
    if (def->m_size == -1) {
        /* Module does not support repeated initialization */
        if (def->m_base.m_copy == NULL)
            return NULL;
        mod = PyImport_AddModule(name);
        if (mod == NULL)
            return NULL;
        mdict = PyModule_GetDict(mod);
        if (mdict == NULL)
            return NULL;
        if (PyDict_Update(mdict, def->m_base.m_copy))
            return NULL;
    }
    else {
        if (def->m_base.m_init == NULL)
            return NULL;
        mod = def->m_base.m_init();
        if (mod == NULL)
            return NULL;
        PyDict_SetItemString(PyImport_GetModuleDict(), name, mod);
        Py_DECREF(mod);
    }
    if (_PyState_AddModule(mod, def) < 0) {
        PyDict_DelItemString(PyImport_GetModuleDict(), name);
        Py_DECREF(mod);
        return NULL;
    }
    if (Py_VerboseFlag)
        PySys_FormatStderr("import %s # previously loaded (%U)\n",
                          name, filename);
    return mod;

}

PyObject *
_PyImport_FindBuiltin(char *name)
{
    PyObject *res, *filename;
    filename = PyUnicode_FromString(name);
    if (filename == NULL)
        return NULL;
    res = _PyImport_FindExtensionUnicode(name, filename);
    Py_DECREF(filename);
    return res;
}

/* 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.
   Because the former action is most common, THIS DOES NOT RETURN A
   'NEW' REFERENCE! */

PyObject *
PyImport_AddModule(const char *name)
{
    PyObject *modules = PyImport_GetModuleDict();
    PyObject *m;

    if ((m = PyDict_GetItemString(modules, name)) != NULL &&
        PyModule_Check(m))
        return m;
    m = PyModule_New(name);
    if (m == NULL)
        return NULL;
    if (PyDict_SetItemString(modules, name, m) != 0) {
        Py_DECREF(m);
        return NULL;
    }
    Py_DECREF(m); /* Yes, it still exists, in modules! */

    return m;
}

/* Remove name from sys.modules, if it's there. */
static void
remove_module(const char *name)
{
    PyObject *modules = PyImport_GetModuleDict();
    if (PyDict_GetItemString(modules, name) == NULL)
        return;
    if (PyDict_DelItemString(modules, name) < 0)
        Py_FatalError("import:  deleting existing key in"
                      "sys.modules failed");
}

static PyObject * get_sourcefile(char *file);
static char *make_source_pathname(char *pathname, char *buf);
static char *make_compiled_pathname(char *pathname, char *buf, size_t buflen,
                                    int debug);

/* 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(char *name, PyObject *co)
{
    return PyImport_ExecCodeModuleWithPathnames(
        name, co, (char *)NULL, (char *)NULL);
}

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

PyObject *
PyImport_ExecCodeModuleWithPathnames(char *name, PyObject *co, char *pathname,
                                     char *cpathname)
{
    PyObject *modules = PyImport_GetModuleDict();
    PyObject *m, *d, *v;

    m = PyImport_AddModule(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);
    if (PyDict_GetItemString(d, "__builtins__") == NULL) {
        if (PyDict_SetItemString(d, "__builtins__",
                                 PyEval_GetBuiltins()) != 0)
            goto error;
    }
    /* Remember the filename as the __file__ attribute */
    v = NULL;
    if (pathname != NULL) {
        v = get_sourcefile(pathname);
        if (v == NULL)
            PyErr_Clear();
    }
    if (v == NULL) {
        v = ((PyCodeObject *)co)->co_filename;
        Py_INCREF(v);
    }
    if (PyDict_SetItemString(d, "__file__", v) != 0)
        PyErr_Clear(); /* Not important enough to report */
    Py_DECREF(v);

    /* Remember the pyc path name as the __cached__ attribute. */
    if (cpathname == NULL) {
        v = Py_None;
        Py_INCREF(v);
    }
    else if ((v = PyUnicode_FromString(cpathname)) == NULL) {
        PyErr_Clear(); /* Not important enough to report */
        v = Py_None;
        Py_INCREF(v);
    }
    if (PyDict_SetItemString(d, "__cached__", v) != 0)
        PyErr_Clear(); /* Not important enough to report */
    Py_DECREF(v);

    v = PyEval_EvalCode(co, d, d);
    if (v == NULL)
        goto error;
    Py_DECREF(v);

    if ((m = PyDict_GetItemString(modules, name)) == NULL) {
        PyErr_Format(PyExc_ImportError,
                     "Loaded module %.200s not found in sys.modules",
                     name);
        return NULL;
    }

    Py_INCREF(m);

    return m;

  error:
    remove_module(name);
    return NULL;
}


/* Like strrchr(string, '/') but searches for the rightmost of either SEP
   or ALTSEP, if the latter is defined.
*/
static char *
rightmost_sep(char *s)
{
    char *found, c;
    for (found = NULL; (c = *s); s++) {
        if (c == SEP
#ifdef ALTSEP
            || c == ALTSEP
#endif
            )
        {
            found = s;
        }
    }
    return found;
}


/* Given a pathname for a Python source file, fill a buffer with the
   pathname for the corresponding compiled file.  Return the pathname
   for the compiled file, or NULL if there's no space in the buffer.
   Doesn't set an exception. */

static char *
make_compiled_pathname(char *pathname, char *buf, size_t buflen, int debug)
{
    /* foo.py -> __pycache__/foo.<tag>.pyc */
    size_t len = strlen(pathname);
    size_t i, save;
    char *pos;
    int sep = SEP;

    /* Sanity check that the buffer has roughly enough space to hold what
       will eventually be the full path to the compiled file.  The 5 extra
       bytes include the slash afer __pycache__, the two extra dots, the
       extra trailing character ('c' or 'o') and null.  This isn't exact
       because the contents of the buffer can affect how many actual
       characters of the string get into the buffer.  We'll do a final
       sanity check before writing the extension to ensure we do not
       overflow the buffer.
    */
    if (len + strlen(CACHEDIR) + strlen(pyc_tag) + 5 > buflen)
        return NULL;

    /* Find the last path separator and copy everything from the start of
       the source string up to and including the separator.
    */
    if ((pos = rightmost_sep(pathname)) == NULL) {
        i = 0;
    }
    else {
        sep = *pos;
        i = pos - pathname + 1;
        strncpy(buf, pathname, i);
    }

    save = i;
    buf[i++] = '\0';
    /* Add __pycache__/ */
    strcat(buf, CACHEDIR);
    i += strlen(CACHEDIR) - 1;
    buf[i++] = sep;
    buf[i++] = '\0';
    /* Add the base filename, but remove the .py or .pyw extension, since
       the tag name must go before the extension.
    */
    strcat(buf, pathname + save);
    if ((pos = strrchr(buf, '.')) != NULL)
        *++pos = '\0';
    strcat(buf, pyc_tag);
    /* The length test above assumes that we're only adding one character
       to the end of what would normally be the extension.  What if there
       is no extension, or the string ends in '.' or '.p', and otherwise
       fills the buffer?  By appending 4 more characters onto the string
       here, we could overrun the buffer.

       As a simple example, let's say buflen=32 and the input string is
       'xxx.py'.  strlen() would be 6 and the test above would yield:

       (6 + 11 + 10 + 5 == 32) > 32

       which is false and so the name mangling would continue.  This would
       be fine because we'd end up with this string in buf:

       __pycache__/xxx.cpython-32.pyc\0

       strlen(of that) == 30 + the nul fits inside a 32 character buffer.
       We can even handle an input string of say 'xxxxx' above because
       that's (5 + 11 + 10 + 5 == 31) > 32 which is also false.  Name
       mangling that yields:

       __pycache__/xxxxxcpython-32.pyc\0

       which is 32 characters including the nul, and thus fits in the
       buffer. However, an input string of 'xxxxxx' would yield a result
       string of:

       __pycache__/xxxxxxcpython-32.pyc\0

       which is 33 characters long (including the nul), thus overflowing
       the buffer, even though the first test would fail, i.e.: the input
       string is also 6 characters long, so 32 > 32 is false.

       The reason the first test fails but we still overflow the buffer is
       that the test above only expects to add one extra character to be
       added to the extension, and here we're adding three (pyc).  We
       don't add the first dot, so that reclaims one of expected
       positions, leaving us overflowing by 1 byte (3 extra - 1 reclaimed
       dot - 1 expected extra == 1 overflowed).

       The best we can do is ensure that we still have enough room in the
       target buffer before we write the extension.  Because it's always
       only the extension that can cause the overflow, and never the other
       path bytes we've written, it's sufficient to just do one more test
       here.  Still, the assertion that follows can't hurt.
    */
#if 0
    printf("strlen(buf): %d; buflen: %d\n", (int)strlen(buf), (int)buflen);
#endif
    if (strlen(buf) + 5 > buflen)
        return NULL;
    strcat(buf, debug ? ".pyc" : ".pyo");
    assert(strlen(buf) < buflen);
    return buf;
}


/* Given a pathname to a Python byte compiled file, return the path to the
   source file, if the path matches the PEP 3147 format.  This does not check
   for any file existence, however, if the pyc file name does not match PEP
   3147 style, NULL is returned.  buf must be at least as big as pathname;
   the resulting path will always be shorter. */

static char *
make_source_pathname(char *pathname, char *buf)
{
    /* __pycache__/foo.<tag>.pyc -> foo.py */
    size_t i, j;
    char *left, *right, *dot0, *dot1, sep;

    /* Look back two slashes from the end.  In between these two slashes
       must be the string __pycache__ or this is not a PEP 3147 style
       path.  It's possible for there to be only one slash.
    */
    if ((right = rightmost_sep(pathname)) == NULL)
        return NULL;
    sep = *right;
    *right = '\0';
    left = rightmost_sep(pathname);
    *right = sep;
    if (left == NULL)
        left = pathname;
    else
        left++;
    if (right-left != strlen(CACHEDIR) ||
        strncmp(left, CACHEDIR, right-left) != 0)
        return NULL;

    /* Now verify that the path component to the right of the last slash
       has two dots in it.
    */
    if ((dot0 = strchr(right + 1, '.')) == NULL)