Re-implement the 'warnings' module in C. This allows for usage of the

'warnings' code in places where it was previously not possible (e.g., the
parser). It could also potentially lead to a speed-up in interpreter start-up
if the C version of the code (_warnings) is imported over the use of the
Python version in key places.

Closes issue #1631171.

5 files changed, 917 insertions, 157 deletions

diff --git a/Python/_warnings.c b/Python/_warnings.c
new file mode 100644
index 0000000..b815927
--- /dev/null
+++ b/Python/_warnings.c
@@ -0,0 +1,856 @@
+#include "Python.h"
+#include "frameobject.h"
+
+#define MODULE_NAME "_warnings"
+#define DEFAULT_ACTION_NAME "default_action"
+
+PyDoc_STRVAR(warnings__doc__,
+MODULE_NAME " provides basic warning filtering support.\n"
+"It is a helper module to speed up interpreter start-up.");
+
+/* Both 'filters' and 'onceregistry' can be set in warnings.py;
+   get_warnings_attr() will reset these variables accordingly. */
+static PyObject *_filters;  /* List */
+static PyObject *_once_registry;  /* Dict */
+
+
+static int
+check_matched(PyObject *obj, PyObject *arg)
+{
+    PyObject *result;
+    int rc;
+
+    if (obj == Py_None)
+        return 1;
+    result = PyObject_CallMethod(obj, "match", "O", arg);
+    if (result == NULL)
+        return -1;
+
+    rc = PyObject_IsTrue(result);
+    Py_DECREF(result);
+    return rc;
+}
+
+/*
+   Returns a new reference.
+   A NULL return value can mean false or an error.
+*/
+static PyObject *
+get_warnings_attr(const char *attr)
+{
+    static PyObject *warnings_str = NULL;
+    PyObject *all_modules;
+    PyObject *warnings_module;
+    int result;
+
+    if (warnings_str == NULL) {
+        warnings_str = PyString_FromString("warnings");
+        if (warnings_str == NULL)
+            return NULL;
+    }
+
+    all_modules = PyImport_GetModuleDict();
+    result = PyDict_Contains(all_modules, warnings_str);
+    if (result == -1 || result == 0)
+        return NULL;
+
+    warnings_module = PyDict_GetItem(all_modules, warnings_str);
+    if (!PyObject_HasAttrString(warnings_module, attr))
+            return NULL;
+    return PyObject_GetAttrString(warnings_module, attr);
+}
+
+
+PyObject *
+get_once_registry(void)
+{
+    PyObject *registry;
+
+    registry = get_warnings_attr("onceregistry");
+    if (registry == NULL) {
+        if (PyErr_Occurred())
+            return NULL;
+        return _once_registry;
+    }
+    Py_DECREF(_once_registry);
+    _once_registry = registry;
+    return registry;
+}
+
+
+/* The item is a borrowed reference. */
+static const char *
+get_filter(PyObject *category, PyObject *text, Py_ssize_t lineno,
+           PyObject *module, PyObject **item)
+{
+    PyObject *action, *m, *d;
+    Py_ssize_t i;
+    PyObject *warnings_filters;
+
+    warnings_filters = get_warnings_attr("filters");
+    if (warnings_filters == NULL) {
+        if (PyErr_Occurred())
+            return NULL;
+    }
+    else {
+        Py_DECREF(_filters);
+        _filters = warnings_filters;
+    }
+
+    if (!PyList_Check(_filters)) {
+        PyErr_SetString(PyExc_ValueError,
+                        MODULE_NAME ".filters must be a list");
+        return NULL;
+    }
+
+    /* _filters could change while we are iterating over it. */
+    for (i = 0; i < PyList_GET_SIZE(_filters); i++) {
+        PyObject *tmp_item, *action, *msg, *cat, *mod, *ln_obj;
+        Py_ssize_t ln;
+        int is_subclass, good_msg, good_mod;
+
+        tmp_item = *item = PyList_GET_ITEM(_filters, i);
+        if (PyTuple_Size(tmp_item) != 5) {
+            PyErr_Format(PyExc_ValueError,
+                         MODULE_NAME ".filters item %zd isn't a 5-tuple", i);
+            return NULL;
+        }
+
+        /* Python code: action, msg, cat, mod, ln = item */
+        action = PyTuple_GET_ITEM(tmp_item, 0);
+        msg = PyTuple_GET_ITEM(tmp_item, 1);
+        cat = PyTuple_GET_ITEM(tmp_item, 2);
+        mod = PyTuple_GET_ITEM(tmp_item, 3);
+        ln_obj = PyTuple_GET_ITEM(tmp_item, 4);
+
+        good_msg = check_matched(msg, text);
+        good_mod = check_matched(mod, module);
+        is_subclass = PyObject_IsSubclass(category, cat);
+        ln = PyInt_AsSsize_t(ln_obj);
+        if (good_msg == -1 || good_mod == -1 || is_subclass == -1 ||
+            (ln == -1 && PyErr_Occurred()))
+            return NULL;
+
+        if (good_msg && is_subclass && good_mod && (ln == 0 || lineno == ln))
+            return PyString_AsString(action);
+    }
+
+    m = PyImport_ImportModule(MODULE_NAME);
+    if (m == NULL)
+        return NULL;
+    d = PyModule_GetDict(m);
+    Py_DECREF(m);
+    if (d == NULL)
+        return NULL;
+    action = PyDict_GetItemString(d, DEFAULT_ACTION_NAME);
+    if (action != NULL)
+        return PyString_AsString(action);
+
+    PyErr_SetString(PyExc_ValueError,
+                    MODULE_NAME "." DEFAULT_ACTION_NAME " not found");
+    return NULL;
+}
+
+static int
+already_warned(PyObject *registry, PyObject *key, int should_set)
+{
+    PyObject *already_warned;
+
+    if (key == NULL)
+        return -1;
+
+    already_warned = PyDict_GetItem(registry, key);
+    if (already_warned != NULL) {
+        int rc = PyObject_IsTrue(already_warned);
+        if (rc != 0)
+            return rc;
+    }
+
+    /* This warning wasn't found in the registry, set it. */
+    if (should_set)
+        return PyDict_SetItem(registry, key, Py_True);
+    return 0;
+}
+
+/* New reference. */
+static PyObject *
+normalize_module(PyObject *filename)
+{
+    PyObject *module;
+    const char *mod_str;
+    Py_ssize_t len;
+
+    int rc = PyObject_IsTrue(filename);
+    if (rc == -1)
+        return NULL;
+    else if (rc == 0)
+        return PyString_FromString("<unknown>");
+
+    mod_str = PyString_AsString(filename);
+    if (mod_str == NULL)
+	    return NULL;
+    len = PyString_Size(filename);
+    if (len < 0)
+        return NULL;
+    if (len >= 3 &&
+	strncmp(mod_str + (len - 3), ".py", 3) == 0) {
+        module = PyString_FromStringAndSize(mod_str, len-3);
+    }
+    else {
+        module = filename;
+        Py_INCREF(module);
+    }
+    return module;
+}
+
+static int
+update_registry(PyObject *registry, PyObject *text, PyObject *category,
+                int add_zero)
+{
+    PyObject *altkey, *zero = NULL;
+    int rc;
+
+    if (add_zero) {
+        zero = PyInt_FromLong(0);
+        if (zero == NULL)
+            return -1;
+        altkey = PyTuple_Pack(3, text, category, zero);
+    }
+    else
+        altkey = PyTuple_Pack(2, text, category);
+
+    rc = already_warned(registry, altkey, 1);
+    Py_XDECREF(zero);
+    Py_XDECREF(altkey);
+    return rc;
+}
+
+static void
+show_warning(PyObject *filename, int lineno, PyObject *text, PyObject
+                *category, PyObject *sourceline)
+{
+    PyObject *f_stderr; 
+    PyObject *name; 
+    char lineno_str[128];
+
+    PyOS_snprintf(lineno_str, sizeof(lineno_str), ":%d: ", lineno);
+
+    name = PyObject_GetAttrString(category, "__name__");
+    if (name == NULL)  /* XXX Can an object lack a '__name__' attribute? */
+	    return;
+
+    f_stderr = PySys_GetObject("stderr");
+    if (f_stderr == NULL) {
+        fprintf(stderr, "lost sys.stderr\n");
+        Py_DECREF(name);
+        return;
+    }
+
+    /* Print "filename:lineno: category: text\n" */
+    PyFile_WriteObject(filename, f_stderr, Py_PRINT_RAW);
+    PyFile_WriteString(lineno_str, f_stderr);
+    PyFile_WriteObject(name, f_stderr, Py_PRINT_RAW);
+    PyFile_WriteString(": ", f_stderr);
+    PyFile_WriteObject(text, f_stderr, Py_PRINT_RAW);
+    PyFile_WriteString("\n", f_stderr);
+    Py_XDECREF(name);
+
+    /* Print "  source_line\n" */
+    PyFile_WriteString("  ", f_stderr);
+    if (sourceline) {
+        char *source_line_str = PyString_AS_STRING(sourceline);
+        while (*source_line_str == ' ' || *source_line_str == '\t' ||
+                *source_line_str == '\014')
+            source_line_str++;
+
+        PyFile_WriteString(source_line_str, f_stderr);
+        PyFile_WriteString("\n", f_stderr);
+    }
+    else
+        Py_DisplaySourceLine(f_stderr, PyString_AS_STRING(filename), lineno);
+    PyErr_Clear();
+}
+
+static PyObject *
+warn_explicit(PyObject *category, PyObject *message, 
+              PyObject *filename, int lineno,
+              PyObject *module, PyObject *registry, PyObject *sourceline)
+{
+    PyObject *key = NULL, *text = NULL, *result = NULL, *lineno_obj = NULL;
+    PyObject *item = Py_None;
+    const char *action;
+    int rc;
+
+    /* Normalize module. */
+    if (module == NULL) {
+        module = normalize_module(filename);
+        if (module == NULL)
+            return NULL;
+    }
+    else
+        Py_INCREF(module);
+
+    /* Normalize message. */
+    Py_INCREF(message);  /* DECREF'ed in cleanup. */
+    rc = PyObject_IsInstance(message, PyExc_Warning);
+    if (rc == -1) {
+        goto cleanup;
+    }
+    if (rc == 1) {
+        text = PyObject_Str(message);
+        category = (PyObject*)message->ob_type;
+    }
+    else {
+        text = message;
+        message = PyObject_CallFunction(category, "O", message);
+    }
+
+    lineno_obj = PyInt_FromLong(lineno);
+    if (lineno_obj == NULL)
+        goto cleanup;
+
+    /* Create key. */
+    key = PyTuple_Pack(3, text, category, lineno_obj);
+    if (key == NULL)
+        goto cleanup;
+
+    if (registry != NULL) {
+        rc = already_warned(registry, key, 0);
+        if (rc == -1)
+            goto cleanup;
+	else if (rc == 1)
+            goto return_none;
+        /* Else this warning hasn't been generated before. */
+    }
+
+    action = get_filter(category, text, lineno, module, &item);
+    if (action == NULL)
+        goto cleanup;
+
+    if (strcmp(action, "error") == 0) {
+        PyErr_SetObject(category, message);
+        goto cleanup;
+    }
+
+    /* Store in the registry that we've been here, *except* when the action
+       is "always". */
+    rc = 0;
+    if (strcmp(action, "always") != 0) {
+        if (registry != NULL && PyDict_SetItem(registry, key, Py_True) < 0)
+            goto cleanup;
+        else if (strcmp(action, "ignore") == 0)
+            goto return_none;
+        else if (strcmp(action, "once") == 0) {
+            if (registry == NULL) {
+                registry = get_once_registry();
+                if (registry == NULL)
+                    goto cleanup;
+            }
+            /* _once_registry[(text, category)] = 1 */
+            rc = update_registry(registry, text, category, 0); 
+        }
+        else if (strcmp(action, "module") == 0) {
+            /* registry[(text, category, 0)] = 1 */
+            if (registry != NULL)
+                rc = update_registry(registry, text, category, 0); 
+        }
+        else if (strcmp(action, "default") != 0) {
+            PyObject *to_str = PyObject_Str(item);
+            const char *err_str = "???";
+
+            if (to_str != NULL)
+                err_str = PyString_AS_STRING(to_str);
+            PyErr_Format(PyExc_RuntimeError,
+                        "Unrecognized action (%s) in warnings.filters:\n %s",
+                        action, err_str);
+            Py_XDECREF(to_str);
+            goto cleanup;
+        }
+    }
+
+    if (rc == 1)  // Already warned for this module. */
+        goto return_none;
+    if (rc == 0) {
+        PyObject *show_fxn = get_warnings_attr("showwarning");
+        if (show_fxn == NULL) {
+            if (PyErr_Occurred())
+                goto cleanup;
+            show_warning(filename, lineno, text, category, sourceline);
+        }
+        else {
+            PyObject *result;
+            
+            result = PyObject_CallFunctionObjArgs(show_fxn, message, category,
+                                                    filename, lineno_obj,
+                                                    Py_None,
+                                                    sourceline ?
+                                                        sourceline: Py_None,
+                                                    NULL);
+            Py_XDECREF(result);
+            if (result == NULL)
+                goto cleanup;
+        }
+    }
+    else /* if (rc == -1) */
+        goto cleanup;
+
+ return_none:
+    result = Py_None;
+    Py_INCREF(result);
+
+ cleanup:
+    Py_XDECREF(key);
+    Py_XDECREF(text);
+    Py_XDECREF(lineno_obj);
+    Py_DECREF(module);
+    Py_DECREF(message);
+    return result;  /* Py_None or NULL. */
+}
+
+/* filename, module, and registry are new refs, globals is borrowed */
+/* Returns 0 on error (no new refs), 1 on success */
+static int
+setup_context(Py_ssize_t stack_level, PyObject **filename, int *lineno,
+              PyObject **module, PyObject **registry)
+{
+    PyObject *globals;
+
+    /* Setup globals and lineno. */
+    PyFrameObject *f = PyThreadState_GET()->frame;
+    while (--stack_level > 0 && f != NULL) {
+        f = f->f_back;
+        --stack_level;
+    }
+
+    if (f == NULL) {
+        globals = PyThreadState_Get()->interp->sysdict;
+        *lineno = 1;
+    }
+    else {
+        globals = f->f_globals;
+        *lineno = PyCode_Addr2Line(f->f_code, f->f_lasti);
+    }
+
+    *module = NULL;
+
+    /* Setup registry. */
+    assert(globals != NULL);
+    assert(PyDict_Check(globals));
+    *registry = PyDict_GetItemString(globals, "__warningregistry__");
+    if (*registry == NULL) {
+        int rc;
+
+        *registry = PyDict_New();
+        if (*registry == NULL)
+            return 0;
+
+         rc = PyDict_SetItemString(globals, "__warningregistry__", *registry);
+         if (rc < 0)
+            goto handle_error;
+    }
+    else
+        Py_INCREF(*registry);
+
+    /* Setup module. */
+    *module = PyDict_GetItemString(globals, "__name__");
+    if (*module == NULL) {
+        *module = PyString_FromString("<string>");
+        if (*module == NULL)
+            goto handle_error;
+    }
+    else
+        Py_INCREF(*module);
+
+    /* Setup filename. */
+    *filename = PyDict_GetItemString(globals, "__file__");
+    if (*filename != NULL) {
+	Py_ssize_t len = PyString_Size(*filename);
+        const char *file_str = PyString_AsString(*filename);
+	if (file_str == NULL || (len < 0 && PyErr_Occurred()))
+            goto handle_error;
+
+        /* if filename.lower().endswith((".pyc", ".pyo")): */
+        if (len >= 4 &&
+            file_str[len-4] == '.' &&
+            tolower(file_str[len-3]) == 'p' &&
+            tolower(file_str[len-2]) == 'y' &&
+            (tolower(file_str[len-1]) == 'c' ||
+             tolower(file_str[len-1]) == 'o')) {
+            *filename = PyString_FromStringAndSize(file_str, len-1);
+	    if (*filename == NULL)
+		    goto handle_error;
+	}
+	else
+            Py_INCREF(*filename);
+    }
+    else {
+        const char *module_str = PyString_AsString(*module);
+        if (module_str && strcmp(module_str, "__main__") == 0) {
+            PyObject *argv = PySys_GetObject("argv");
+            if (argv != NULL && PyList_Size(argv) > 0) {
+                *filename = PyList_GetItem(argv, 0);
+                Py_INCREF(*filename);
+            }
+            else {
+                /* embedded interpreters don't have sys.argv, see bug #839151 */
+                *filename = PyString_FromString("__main__");
+	        if (*filename == NULL)
+	            goto handle_error;
+            }
+        }
+        if (*filename == NULL) {
+            *filename = *module;
+            Py_INCREF(*filename);
+        }
+    }
+
+    return 1;
+
+ handle_error:
+    /* filename not XDECREF'ed here as there is no way to jump here with a
+       dangling reference. */
+    Py_XDECREF(*registry);
+    Py_XDECREF(*module);
+    return 0;
+}
+
+static PyObject *
+get_category(PyObject *message, PyObject *category)
+{
+    int rc;
+
+    /* Get category. */
+    rc = PyObject_IsInstance(message, PyExc_Warning);
+    if (rc == -1)
+        return NULL;
+
+    if (rc == 1)
+        category = (PyObject*)message->ob_type;
+    else if (category == NULL)
+        category = PyExc_UserWarning;
+
+    /* Validate category. */
+    rc = PyObject_IsSubclass(category, PyExc_Warning);
+    if (rc == -1)
+        return NULL;
+    if (rc == 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "category is not a subclass of Warning");
+        return NULL;
+    }
+
+    return category;
+}
+
+static PyObject *
+do_warn(PyObject *message, PyObject *category, Py_ssize_t stack_level)
+{
+    PyObject *filename, *module, *registry, *res;
+    int lineno;
+
+    if (!setup_context(stack_level, &filename, &lineno, &module, &registry))
+        return NULL;
+
+    res = warn_explicit(category, message, filename, lineno, module, registry,
+                        NULL);
+    Py_DECREF(filename);
+    Py_DECREF(registry);
+    Py_DECREF(module);
+    return res;
+}
+
+static PyObject *
+warnings_warn(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *kw_list[] = { "message", "category", "stacklevel", 0 };
+    PyObject *message, *category = NULL;
+    Py_ssize_t stack_level = 1;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|On:warn", kw_list, 
+                                     &message, &category, &stack_level))
+        return NULL;
+
+    category = get_category(message, category);
+    if (category == NULL)
+        return NULL;
+    return do_warn(message, category, stack_level);
+}
+
+static PyObject *
+warnings_warn_explicit(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *kwd_list[] = {"message", "category", "filename", "lineno",
+                                "module", "registry", "module_globals", 0};
+    PyObject *message;
+    PyObject *category;
+    PyObject *filename;
+    int lineno;
+    PyObject *module = NULL;
+    PyObject *registry = NULL;
+    PyObject *module_globals = NULL;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "OOOi|OOO:warn_explicit",
+                kwd_list, &message, &category, &filename, &lineno, &module,
+                &registry, &module_globals))
+        return NULL;
+
+    if (module_globals) {
+        static PyObject *get_source_name = NULL;
+        static PyObject *splitlines_name = NULL;
+        PyObject *loader;
+        PyObject *module_name;
+        PyObject *source;
+        PyObject *source_list;
+        PyObject *source_line;
+        PyObject *returned;
+
+        if (get_source_name == NULL) {
+            get_source_name = PyString_FromString("get_source");
+            if (!get_source_name)
+                return NULL;
+        }
+        if (splitlines_name == NULL) {
+            splitlines_name = PyString_FromString("splitlines");
+            if (!splitlines_name)
+                return NULL;
+        }
+
+        /* Check/get the requisite pieces needed for the loader. */
+        loader = PyDict_GetItemString(module_globals, "__loader__");
+        module_name = PyDict_GetItemString(module_globals, "__name__");
+
+        if (loader == NULL || module_name == NULL)
+            goto standard_call;
+
+        /* Make sure the loader implements the optional get_source() method. */
+        if (!PyObject_HasAttrString(loader, "get_source"))
+                goto standard_call;
+        /* Call get_source() to get the source code. */
+        source = PyObject_CallMethodObjArgs(loader, get_source_name,
+                                                module_name, NULL);
+        if (!source)
+            return NULL;
+        else if (source == Py_None) {
+            Py_DECREF(Py_None);
+            goto standard_call;
+        }
+
+        /* Split the source into lines. */
+        source_list = PyObject_CallMethodObjArgs(source, splitlines_name,
+                                                    NULL);
+        Py_DECREF(source);
+        if (!source_list)
+            return NULL;
+
+        /* Get the source line. */
+        source_line = PyList_GetItem(source_list, lineno-1);
+        if (!source_line) {
+            Py_DECREF(source_list);
+            return NULL;
+        }
+
+        /* Handle the warning. */
+        returned = warn_explicit(category, message, filename, lineno, module,
+                            registry, source_line);
+        Py_DECREF(source_list);
+        return returned;
+    }
+
+ standard_call:
+    return warn_explicit(category, message, filename, lineno, module,
+                                registry, NULL);
+}
+
+
+/* Function to issue a warning message; may raise an exception. */
+int
+PyErr_WarnEx(PyObject *category, const char *text, Py_ssize_t stack_level)
+{
+    PyObject *res;
+    PyObject *message = PyString_FromString(text);
+    if (message == NULL)
+        return -1;
+
+    if (category == NULL)
+        category = PyExc_RuntimeWarning;
+
+    res = do_warn(message, category, stack_level);
+    Py_DECREF(message);
+    if (res == NULL)
+        return -1;
+    Py_DECREF(res);
+
+    return 0;
+}
+
+/* PyErr_Warn is only for backwards compatability and will be removed.
+   Use PyErr_WarnEx instead. */
+
+#undef PyErr_Warn
+
+PyAPI_FUNC(int)
+PyErr_Warn(PyObject *category, char *text)
+{
+    return PyErr_WarnEx(category, text, 1);
+}
+
+/* Warning with explicit origin */
+int
+PyErr_WarnExplicit(PyObject *category, const char *text,
+                   const char *filename_str, int lineno,
+                   const char *module_str, PyObject *registry)
+{
+    PyObject *res;
+    PyObject *message = PyString_FromString(text);
+    PyObject *filename = PyString_FromString(filename_str);
+    PyObject *module = NULL;
+    int ret = -1;
+
+    if (message == NULL || filename == NULL)
+        goto exit;
+    if (module_str != NULL) {
+        module = PyString_FromString(module_str);
+            if (module == NULL)
+                goto exit;
+    }
+
+    if (category == NULL)
+        category = PyExc_RuntimeWarning;
+    res = warn_explicit(category, message, filename, lineno, module, registry,
+                        NULL);
+    if (res == NULL)
+        goto exit;
+    Py_DECREF(res);
+    ret = 0;
+
+ exit:
+    Py_XDECREF(message);
+    Py_XDECREF(module);
+    Py_XDECREF(filename);
+    return ret;
+}
+
+
+PyDoc_STRVAR(warn_doc,
+"Issue a warning, or maybe ignore it or raise an exception.");
+
+PyDoc_STRVAR(warn_explicit_doc,
+"Low-level inferface to warnings functionality.");
+
+static PyMethodDef warnings_functions[] = {
+    {"warn", (PyCFunction)warnings_warn, METH_VARARGS | METH_KEYWORDS,
+        warn_doc},
+    {"warn_explicit", (PyCFunction)warnings_warn_explicit,
+        METH_VARARGS | METH_KEYWORDS, warn_explicit_doc},
+    // XXX(brett.cannon): add showwarning?
+    // XXX(brett.cannon): Reasonable to add formatwarning?
+    {NULL, NULL}	        /* sentinel */
+};
+
+
+static PyObject *
+create_filter(PyObject *category, const char *action)
+{
+    static PyObject *ignore_str = NULL;
+    static PyObject *error_str = NULL;
+    static PyObject *default_str = NULL;
+    PyObject *action_obj = NULL;
+    PyObject *lineno, *result;
+
+    if (!strcmp(action, "ignore")) {
+        if (ignore_str == NULL) {
+            ignore_str = PyString_InternFromString("ignore");
+            if (ignore_str == NULL)
+                return NULL;
+        }
+        action_obj = ignore_str;
+    }
+    else if (!strcmp(action, "error")) {
+        if (error_str == NULL) {
+            error_str = PyString_InternFromString("error");
+            if (error_str == NULL)
+                return NULL;
+        }
+        action_obj = error_str;
+    }
+    else if (!strcmp(action, "default")) {
+        if (default_str == NULL) {
+            default_str = PyString_InternFromString("default");
+            if (default_str == NULL)
+                return NULL;
+        }
+        action_obj = default_str;
+    }
+    else {
+        Py_FatalError("unknown action");
+    }
+
+    /* This assumes the line number is zero for now. */
+    lineno = PyInt_FromLong(0);
+    if (lineno == NULL)
+        return NULL;
+    result = PyTuple_Pack(5, action_obj, Py_None, category, Py_None, lineno);
+    Py_DECREF(lineno);
+    return result;
+}
+
+static PyObject *
+init_filters(void)
+{
+    PyObject *filters = PyList_New(3);
+    const char *bytes_action;
+    if (filters == NULL)
+        return NULL;
+
+    PyList_SET_ITEM(filters, 0,
+                    create_filter(PyExc_PendingDeprecationWarning, "ignore"));
+    PyList_SET_ITEM(filters, 1, create_filter(PyExc_ImportWarning, "ignore"));
+    if (Py_BytesWarningFlag > 1)
+        bytes_action = "error";
+    else if (Py_BytesWarningFlag)
+        bytes_action = "default";
+    else
+        bytes_action = "ignore";
+    PyList_SET_ITEM(filters, 2, create_filter(PyExc_BytesWarning,
+                    bytes_action));
+
+    if (PyList_GET_ITEM(filters, 0) == NULL ||
+        PyList_GET_ITEM(filters, 1) == NULL ||
+        PyList_GET_ITEM(filters, 2) == NULL) {
+        Py_DECREF(filters);
+        return NULL;
+    }
+
+    return filters;
+}
+
+
+PyMODINIT_FUNC
+_PyWarnings_Init(void)
+{
+    PyObject *m, *default_action;
+
+    m = Py_InitModule3(MODULE_NAME, warnings_functions, warnings__doc__);
+    if (m == NULL)
+        return;
+
+    _filters = init_filters();
+    if (_filters == NULL)
+        return;
+    Py_INCREF(_filters);
+    if (PyModule_AddObject(m, "filters", _filters) < 0)
+        return;
+
+    _once_registry = PyDict_New();
+    if (_once_registry == NULL)
+        return;
+    Py_INCREF(_once_registry);
+    if (PyModule_AddObject(m, "once_registry", _once_registry) < 0)
+        return;
+
+    default_action = PyString_InternFromString("default");
+    if (default_action == NULL)
+        return;
+    if (PyModule_AddObject(m, DEFAULT_ACTION_NAME, default_action) < 0)
+        return;
+}
diff --git a/Python/errors.c b/Python/errors.c
index 1c29160..8951d57 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -641,81 +641,6 @@ PyErr_WriteUnraisable(PyObject *obj)
 
 extern PyObject *PyModule_GetWarningsModule(void);
 
-/* Function to issue a warning message; may raise an exception. */
-int
-PyErr_WarnEx(PyObject *category, const char *message, Py_ssize_t stack_level)
-{
-	PyObject *dict, *func = NULL;
-	PyObject *warnings_module = PyModule_GetWarningsModule();
-
-	if (warnings_module != NULL) {
-		dict = PyModule_GetDict(warnings_module);
-		if (dict != NULL)
-			func = PyDict_GetItemString(dict, "warn");
-	}
-	if (func == NULL) {
-		PySys_WriteStderr("warning: %s\n", message);
-		return 0;
-	}
-	else {
-		PyObject *res;
-
-		if (category == NULL)
-			category = PyExc_RuntimeWarning;
-		res = PyObject_CallFunction(func, "sOn",
-					    message, category, stack_level);
-		if (res == NULL)
-			return -1;
-		Py_DECREF(res);
-		return 0;
-	}
-}
-
-/* PyErr_Warn is only for backwards compatability and will be removed.
-   Use PyErr_WarnEx instead. */
-
-#undef PyErr_Warn
-
-PyAPI_FUNC(int)
-PyErr_Warn(PyObject *category, char *message)
-{
-	return PyErr_WarnEx(category, message, 1);
-}
-
-/* Warning with explicit origin */
-int
-PyErr_WarnExplicit(PyObject *category, const char *message,
-		   const char *filename, int lineno,
-		   const char *module, PyObject *registry)
-{
-	PyObject *mod, *dict, *func = NULL;
-
-	mod = PyImport_ImportModuleNoBlock("warnings");
-	if (mod != NULL) {
-		dict = PyModule_GetDict(mod);
-		func = PyDict_GetItemString(dict, "warn_explicit");
-		Py_DECREF(mod);
-	}
-	if (func == NULL) {
-		PySys_WriteStderr("warning: %s\n", message);
-		return 0;
-	}
-	else {
-		PyObject *res;
-
-		if (category == NULL)
-			category = PyExc_RuntimeWarning;
-		if (registry == NULL)
-			registry = Py_None;
-		res = PyObject_CallFunction(func, "sOsizO", message, category,
-					    filename, lineno, module, registry);
-		if (res == NULL)
-			return -1;
-		Py_DECREF(res);
-		return 0;
-	}
-}
-
 
 /* Set file and line information for the current exception.
    If the exception is not a SyntaxError, also sets additional attributes
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 6cc9f6d..a9b7f81 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -83,38 +83,12 @@ int Py_IgnoreEnvironmentFlag; /* e.g. PYTHONPATH, PYTHONHOME */
   true divisions (which they will be in 2.3). */
 int _Py_QnewFlag = 0;
 
-/* Reference to 'warnings' module, to avoid importing it
-   on the fly when the import lock may be held.  See 683658/771097
-*/
-static PyObject *warnings_module = NULL;
-
-/* Returns a borrowed reference to the 'warnings' module, or NULL.
-   If the module is returned, it is guaranteed to have been obtained
-   without acquiring the import lock
-*/
-PyObject *PyModule_GetWarningsModule(void)
-{
-	PyObject *typ, *val, *tb;
-	PyObject *all_modules;
-	/* If we managed to get the module at init time, just use it */
-	if (warnings_module)
-		return warnings_module;
-	/* If it wasn't available at init time, it may be available
-	   now in sys.modules (common scenario is frozen apps: import
-	   at init time fails, but the frozen init code sets up sys.path
-	   correctly, then does an implicit import of warnings for us
-	*/
-	/* Save and restore any exceptions */
-	PyErr_Fetch(&typ, &val, &tb);
-
-	all_modules = PySys_GetObject("modules");
-	if (all_modules) {
-		warnings_module = PyDict_GetItemString(all_modules, "warnings");
-		/* We keep a ref in the global */
-		Py_XINCREF(warnings_module);
-	}
-	PyErr_Restore(typ, val, tb);
-	return warnings_module;
+/* PyModule_GetWarningsModule is no longer necessary as of 2.6
+since _warnings is builtin.  This API should not be used. */
+PyObject *
+PyModule_GetWarningsModule(void)
+{
+	return PyImport_ImportModule("warnings");
 }
 
 static int initialized = 0;
@@ -244,6 +218,15 @@ Py_InitializeEx(int install_sigs)
 
 	if (install_sigs)
 		initsigs(); /* Signal handling stuff, including initintr() */
+		
+    /* Initialize warnings. */
+    _PyWarnings_Init();
+    if (PySys_HasWarnOptions()) {
+        PyObject *warnings_module = PyImport_ImportModule("warnings");
+        if (!warnings_module)
+            PyErr_Clear();
+        Py_XDECREF(warnings_module);
+    }
 
 	initmain(); /* Module __main__ */
 	if (!Py_NoSiteFlag)
@@ -254,30 +237,6 @@ Py_InitializeEx(int install_sigs)
 	_PyGILState_Init(interp, tstate);
 #endif /* WITH_THREAD */
 
-	warnings_module = PyImport_ImportModule("warnings");
-	if (!warnings_module) {
-		PyErr_Clear();
-	}
-	else {
-		PyObject *o;
-		char *action[8];
-
-		if (Py_BytesWarningFlag > 1)
-			*action = "error";
-		else if (Py_BytesWarningFlag)
-			*action = "default";
-		else
-			*action = "ignore";
-
-		o = PyObject_CallMethod(warnings_module,
-					"simplefilter", "sO",
-					*action, PyExc_BytesWarning);
-		if (o == NULL)
-			Py_FatalError("Py_Initialize: can't initialize"
-				      "warning filter for BytesWarning.");
-		Py_DECREF(o);
-        }
-
 #if defined(Py_USING_UNICODE) && defined(HAVE_LANGINFO_H) && defined(CODESET)
 	/* On Unix, set the file system encoding according to the
 	   user's preference, if the CODESET names a well-known
@@ -397,10 +356,6 @@ Py_Finalize(void)
 	/* Disable signal handling */
 	PyOS_FiniInterrupts();
 
-	/* drop module references we saved */
-	Py_XDECREF(warnings_module);
-	warnings_module = NULL;
-
 	/* Clear type lookup cache */
 	PyType_ClearCache();
 
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index e733cee..d6ccd17 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -940,6 +940,12 @@ PySys_AddWarnOption(char *s)
 	}
 }
 
+int
+PySys_HasWarnOptions(void)
+{
+    return warnoptions ? 1 : 0;
+}
+
 /* XXX This doc string is too long to be a single string literal in VC++ 5.0.
    Two literals concatenated works just fine.  If you have a K&R compiler
    or other abomination that however *does* understand longer strings,
@@ -1165,6 +1171,7 @@ static PyStructSequence_Field flags_fields[] = {
 	/* {"unbuffered",		"-u"}, */
 	{"unicode",		"-U"},
 	/* {"skip_first",		"-x"}, */
+	{"bytes_warning", "-b"},
 	{0}
 };
 
@@ -1211,6 +1218,7 @@ make_flags(void)
 	/* SetFlag(saw_unbuffered_flag); */
 	SetFlag(Py_UnicodeFlag);
 	/* SetFlag(skipfirstline); */
+    SetFlag(Py_BytesWarningFlag);
 #undef SetFlag
 
 	if (PyErr_Occurred()) {
diff --git a/Python/traceback.c b/Python/traceback.c
index 877ca5a..7433997 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -122,16 +122,16 @@ PyTraceBack_Here(PyFrameObject *frame)
 	return 0;
 }
 
-static int
-tb_displayline(PyObject *f, char *filename, int lineno, char *name)
+int
+Py_DisplaySourceLine(PyObject *f, const char *filename, int lineno)
 {
 	int err = 0;
-	FILE *xfp;
+	FILE *xfp = NULL;
 	char linebuf[2000];
 	int i;
 	char namebuf[MAXPATHLEN+1];
 
-	if (filename == NULL || name == NULL)
+	if (filename == NULL)
 		return -1;
 	/* This is needed by Emacs' compile command */
 #define FMT "  File \"%.500s\", line %d, in %.500s\n"
@@ -139,7 +139,7 @@ tb_displayline(PyObject *f, char *filename, int lineno, char *name)
 	if (xfp == NULL) {
 		/* Search tail of filename in sys.path before giving up */
 		PyObject *path;
-		char *tail = strrchr(filename, SEP);
+		const char *tail = strrchr(filename, SEP);
 		if (tail == NULL)
 			tail = filename;
 		else
@@ -175,14 +175,14 @@ tb_displayline(PyObject *f, char *filename, int lineno, char *name)
 			}
 		}
 	}
-	PyOS_snprintf(linebuf, sizeof(linebuf), FMT, filename, lineno, name);
-	err = PyFile_WriteString(linebuf, f);
-	if (xfp == NULL)
-		return err;
-	else if (err != 0) {
-		fclose(xfp);
-		return err;
-	}
+
+        if (xfp == NULL)
+            return err;
+        if (err != 0) {
+            fclose(xfp);
+            return err;
+        }
+
 	for (i = 0; i < lineno; i++) {
 		char* pLastChar = &linebuf[sizeof(linebuf)-2];
 		do {
@@ -200,22 +200,38 @@ tb_displayline(PyObject *f, char *filename, int lineno, char *name)
 		char *p = linebuf;
 		while (*p == ' ' || *p == '\t' || *p == '\014')
 			p++;
-		err = PyFile_WriteString("    ", f);
-		if (err == 0) {
-			err = PyFile_WriteString(p, f);
-			if (err == 0 && strchr(p, '\n') == NULL)
-				err = PyFile_WriteString("\n", f);
-		}
+                    err = PyFile_WriteString(p, f);
+                    if (err == 0 && strchr(p, '\n') == NULL)
+                            err = PyFile_WriteString("\n", f);
 	}
 	fclose(xfp);
 	return err;
 }
 
 static int
-tb_printinternal(PyTracebackObject *tb, PyObject *f, int limit)
+tb_displayline(PyObject *f, const char *filename, int lineno, const char *name)
+{
+	int err = 0;
+        char linebuf[2000];
+
+	if (filename == NULL || name == NULL)
+		return -1;
+	/* This is needed by Emacs' compile command */
+#define FMT "  File \"%.500s\", line %d, in %.500s\n"
+	PyOS_snprintf(linebuf, sizeof(linebuf), FMT, filename, lineno, name);
+	err = PyFile_WriteString(linebuf, f);
+	if (err != 0)
+		return err;
+
+        err = PyFile_WriteString("    ", f);
+        return Py_DisplaySourceLine(f, filename, lineno);
+}
+
+static int
+tb_printinternal(PyTracebackObject *tb, PyObject *f, long limit)
 {
 	int err = 0;
-	int depth = 0;
+	long depth = 0;
 	PyTracebackObject *tb1 = tb;
 	while (tb1 != NULL) {
 		depth++;
@@ -242,7 +258,7 @@ PyTraceBack_Print(PyObject *v, PyObject *f)
 {
 	int err;
 	PyObject *limitv;
-	int limit = 1000;
+	long limit = 1000;
 	if (v == NULL)
 		return 0;
 	if (!PyTraceBack_Check(v)) {