cpython/Objects/frameobject.c

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/***********************************************************
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Copyright (c) 2000, BeOpen.com.
Copyright (c) 1995-2000, Corporation for National Research Initiatives.
Copyright (c) 1990-1995, Stichting Mathematisch Centrum.
All rights reserved.
See the file "Misc/COPYRIGHT" for information on usage and
redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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******************************************************************/
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/* Frame object implementation */
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#include "Python.h"
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#include "compile.h"
#include "frameobject.h"
#include "opcode.h"
#include "structmember.h"
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#define OFF(x) offsetof(PyFrameObject, x)
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static struct memberlist frame_memberlist[] = {
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{"f_back", T_OBJECT, OFF(f_back), RO},
{"f_code", T_OBJECT, OFF(f_code), RO},
{"f_builtins", T_OBJECT, OFF(f_builtins),RO},
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{"f_globals", T_OBJECT, OFF(f_globals), RO},
{"f_locals", T_OBJECT, OFF(f_locals), RO},
{"f_lasti", T_INT, OFF(f_lasti), RO},
{"f_lineno", T_INT, OFF(f_lineno), RO},
{"f_restricted",T_INT, OFF(f_restricted),RO},
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{"f_trace", T_OBJECT, OFF(f_trace)},
{"f_exc_type", T_OBJECT, OFF(f_exc_type)},
{"f_exc_value", T_OBJECT, OFF(f_exc_value)},
{"f_exc_traceback", T_OBJECT, OFF(f_exc_traceback)},
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{NULL} /* Sentinel */
};
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static PyObject *
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frame_getattr(PyFrameObject *f, char *name)
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{
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if (strcmp(name, "f_locals") == 0)
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PyFrame_FastToLocals(f);
return PyMember_Get((char *)f, frame_memberlist, name);
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}
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static int
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frame_setattr(PyFrameObject *f, char *name, PyObject *value)
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{
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return PyMember_Set((char *)f, frame_memberlist, name, value);
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}
/* Stack frames are allocated and deallocated at a considerable rate.
In an attempt to improve the speed of function calls, we maintain a
separate free list of stack frames (just like integers are
allocated in a special way -- see intobject.c). When a stack frame
is on the free list, only the following members have a meaning:
ob_type == &Frametype
f_back next item on free list, or NULL
f_nlocals number of locals
f_stacksize size of value stack
Note that the value and block stacks are preserved -- this can save
another malloc() call or two (and two free() calls as well!).
Also note that, unlike for integers, each frame object is a
malloc'ed object in its own right -- it is only the actual calls to
malloc() that we are trying to save here, not the administration.
After all, while a typical program may make millions of calls, a
call depth of more than 20 or 30 is probably already exceptional
unless the program contains run-away recursion. I hope.
*/
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static PyFrameObject *free_list = NULL;
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static void
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frame_dealloc(PyFrameObject *f)
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{
int i;
PyObject **fastlocals;
Py_TRASHCAN_SAFE_BEGIN(f)
/* Kill all local variables */
fastlocals = f->f_localsplus;
for (i = f->f_nlocals; --i >= 0; ++fastlocals) {
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Py_XDECREF(*fastlocals);
}
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Py_XDECREF(f->f_back);
Py_XDECREF(f->f_code);
Py_XDECREF(f->f_builtins);
Py_XDECREF(f->f_globals);
Py_XDECREF(f->f_locals);
Py_XDECREF(f->f_trace);
Py_XDECREF(f->f_exc_type);
Py_XDECREF(f->f_exc_value);
Py_XDECREF(f->f_exc_traceback);
f->f_back = free_list;
free_list = f;
Py_TRASHCAN_SAFE_END(f)
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}
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PyTypeObject PyFrame_Type = {
PyObject_HEAD_INIT(&PyType_Type)
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0,
"frame",
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sizeof(PyFrameObject),
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0,
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(destructor)frame_dealloc, /*tp_dealloc*/
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0, /*tp_print*/
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(getattrfunc)frame_getattr, /*tp_getattr*/
(setattrfunc)frame_setattr, /*tp_setattr*/
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0, /*tp_compare*/
0, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
};
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PyFrameObject *
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PyFrame_New(PyThreadState *tstate, PyCodeObject *code,
PyObject *globals, PyObject *locals)
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{
PyFrameObject *back = tstate->frame;
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static PyObject *builtin_object;
PyFrameObject *f;
PyObject *builtins;
int extras;
if (builtin_object == NULL) {
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builtin_object = PyString_InternFromString("__builtins__");
if (builtin_object == NULL)
return NULL;
}
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if ((back != NULL && !PyFrame_Check(back)) ||
code == NULL || !PyCode_Check(code) ||
globals == NULL || !PyDict_Check(globals) ||
(locals != NULL && !PyDict_Check(locals))) {
PyErr_BadInternalCall();
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return NULL;
}
extras = code->co_stacksize + code->co_nlocals;
if (back == NULL || back->f_globals != globals) {
builtins = PyDict_GetItem(globals, builtin_object);
if (builtins != NULL && PyModule_Check(builtins))
builtins = PyModule_GetDict(builtins);
}
else {
/* If we share the globals, we share the builtins.
Save a lookup and a call. */
builtins = back->f_builtins;
}
if (builtins != NULL && !PyDict_Check(builtins))
builtins = NULL;
if (free_list == NULL) {
/* PyObject_New is inlined */
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f = (PyFrameObject *)
PyObject_MALLOC(sizeof(PyFrameObject) +
extras*sizeof(PyObject *));
if (f == NULL)
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return (PyFrameObject *)PyErr_NoMemory();
PyObject_INIT(f, &PyFrame_Type);
}
else {
f = free_list;
free_list = free_list->f_back;
if (f->f_nlocals + f->f_stacksize < extras) {
f = (PyFrameObject *)
PyObject_REALLOC(f, sizeof(PyFrameObject) +
extras*sizeof(PyObject *));
if (f == NULL)
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return (PyFrameObject *)PyErr_NoMemory();
}
else
extras = f->f_nlocals + f->f_stacksize;
PyObject_INIT(f, &PyFrame_Type);
}
if (builtins == NULL) {
/* No builtins! Make up a minimal one. */
builtins = PyDict_New();
if (builtins == NULL || /* Give them 'None', at least. */
PyDict_SetItemString(builtins, "None", Py_None) < 0) {
Py_DECREF(f);
return NULL;
}
}
else
Py_XINCREF(builtins);
f->f_builtins = builtins;
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Py_XINCREF(back);
f->f_back = back;
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Py_INCREF(code);
f->f_code = code;
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Py_INCREF(globals);
f->f_globals = globals;
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if (code->co_flags & CO_NEWLOCALS) {
if (code->co_flags & CO_OPTIMIZED)
locals = NULL; /* Let fast_2_locals handle it */
else {
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locals = PyDict_New();
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if (locals == NULL) {
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Py_DECREF(f);
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return NULL;
}
}
}
else {
if (locals == NULL)
locals = globals;
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Py_INCREF(locals);
}
f->f_locals = locals;
f->f_trace = NULL;
f->f_exc_type = f->f_exc_value = f->f_exc_traceback = NULL;
f->f_tstate = tstate;
f->f_lasti = 0;
f->f_lineno = code->co_firstlineno;
f->f_restricted = (builtins != tstate->interp->builtins);
f->f_iblock = 0;
f->f_nlocals = code->co_nlocals;
f->f_stacksize = extras - code->co_nlocals;
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while (--extras >= 0)
f->f_localsplus[extras] = NULL;
f->f_valuestack = f->f_localsplus + f->f_nlocals;
return f;
}
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/* Block management */
void
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PyFrame_BlockSetup(PyFrameObject *f, int type, int handler, int level)
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{
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PyTryBlock *b;
if (f->f_iblock >= CO_MAXBLOCKS)
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Py_FatalError("XXX block stack overflow");
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b = &f->f_blockstack[f->f_iblock++];
b->b_type = type;
b->b_level = level;
b->b_handler = handler;
}
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PyTryBlock *
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PyFrame_BlockPop(PyFrameObject *f)
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{
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PyTryBlock *b;
if (f->f_iblock <= 0)
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Py_FatalError("XXX block stack underflow");
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b = &f->f_blockstack[--f->f_iblock];
return b;
}
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/* Convert between "fast" version of locals and dictionary version */
void
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PyFrame_FastToLocals(PyFrameObject *f)
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{
/* Merge fast locals into f->f_locals */
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PyObject *locals, *map;
PyObject **fast;
PyObject *error_type, *error_value, *error_traceback;
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int j;
if (f == NULL)
return;
locals = f->f_locals;
if (locals == NULL) {
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locals = f->f_locals = PyDict_New();
if (locals == NULL) {
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PyErr_Clear(); /* Can't report it :-( */
return;
}
}
if (f->f_nlocals == 0)
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return;
map = f->f_code->co_varnames;
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if (!PyDict_Check(locals) || !PyTuple_Check(map))
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return;
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PyErr_Fetch(&error_type, &error_value, &error_traceback);
fast = f->f_localsplus;
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j = PyTuple_Size(map);
if (j > f->f_nlocals)
j = f->f_nlocals;
for (; --j >= 0; ) {
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PyObject *key = PyTuple_GetItem(map, j);
PyObject *value = fast[j];
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if (value == NULL) {
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PyErr_Clear();
if (PyDict_DelItem(locals, key) != 0)
PyErr_Clear();
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}
else {
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if (PyDict_SetItem(locals, key, value) != 0)
PyErr_Clear();
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}
}
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PyErr_Restore(error_type, error_value, error_traceback);
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}
void
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PyFrame_LocalsToFast(PyFrameObject *f, int clear)
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{
/* Merge f->f_locals into fast locals */
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PyObject *locals, *map;
PyObject **fast;
PyObject *error_type, *error_value, *error_traceback;
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int j;
if (f == NULL)
return;
locals = f->f_locals;
map = f->f_code->co_varnames;
if (locals == NULL || f->f_code->co_nlocals == 0)
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return;
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if (!PyDict_Check(locals) || !PyTuple_Check(map))
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return;
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PyErr_Fetch(&error_type, &error_value, &error_traceback);
fast = f->f_localsplus;
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j = PyTuple_Size(map);
if (j > f->f_nlocals)
j = f->f_nlocals;
for (; --j >= 0; ) {
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PyObject *key = PyTuple_GetItem(map, j);
PyObject *value = PyDict_GetItem(locals, key);
Py_XINCREF(value);
if (value != NULL || clear) {
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Py_XDECREF(fast[j]);
fast[j] = value;
}
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}
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PyErr_Restore(error_type, error_value, error_traceback);
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}
/* Clear out the free list */
void
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PyFrame_Fini(void)
{
while (free_list != NULL) {
PyFrameObject *f = free_list;
free_list = free_list->f_back;
PyObject_DEL(f);
}
}