bpo-43693: Un-revert commits 2c1e258 and b2bf2bc. (gh-26577)

These were reverted in gh-26530 (commit 17c4edc) due to refleaks.

* 2c1e258 - Compute deref offsets in compiler (gh-25152)
* b2bf2bc - Add new internal code objects fields: co_fastlocalnames and co_fastlocalkinds. (gh-26388)

This change fixes the refleaks.

https://bugs.python.org/issue43693

Author: ericsnowcurrently

Doc/library/dis.rst

@@ -1058,17 +1058,24 @@ All of the following opcodes use their arguments.
 
 .. opcode:: LOAD_CLOSURE (i)
 
-   Pushes a reference to the cell contained in slot *i* of the cell and free
-   variable storage.  The name of the variable is ``co_cellvars[i]`` if *i* is
-   less than the length of *co_cellvars*.  Otherwise it is ``co_freevars[i -
-   len(co_cellvars)]``.
+   Pushes a reference to the cell contained in slot ``i`` of the "fast locals"
+   storage.  The name of the variable is ``co_fastlocalnames[i]``.
+
+   Note that ``LOAD_CLOSURE`` is effectively an alias for ``LOAD_FAST``.
+   It exists to keep bytecode a little more readable.
+
+   .. versionchanged:: 3.11
+      ``i`` is no longer offset by the length of ``co_varnames``.
 
 
 .. opcode:: LOAD_DEREF (i)
 
-   Loads the cell contained in slot *i* of the cell and free variable storage.
+   Loads the cell contained in slot ``i`` of the "fast locals" storage.
    Pushes a reference to the object the cell contains on the stack.
 
+   .. versionchanged:: 3.11
+      ``i`` is no longer offset by the length of ``co_varnames``.
+
 
 .. opcode:: LOAD_CLASSDEREF (i)
 
@@ -1078,20 +1085,29 @@ All of the following opcodes use their arguments.
 
    .. versionadded:: 3.4
 
+   .. versionchanged:: 3.11
+      ``i`` is no longer offset by the length of ``co_varnames``.
+
 
 .. opcode:: STORE_DEREF (i)
 
-   Stores TOS into the cell contained in slot *i* of the cell and free variable
+   Stores TOS into the cell contained in slot ``i`` of the "fast locals"
    storage.
 
+   .. versionchanged:: 3.11
+      ``i`` is no longer offset by the length of ``co_varnames``.
+
 
 .. opcode:: DELETE_DEREF (i)
 
-   Empties the cell contained in slot *i* of the cell and free variable storage.
+   Empties the cell contained in slot ``i`` of the "fast locals" storage.
    Used by the :keyword:`del` statement.
 
    .. versionadded:: 3.2
 
+   .. versionchanged:: 3.11
+      ``i`` is no longer offset by the length of ``co_varnames``.
+
 
 .. opcode:: RAISE_VARARGS (argc)
 

Include/cpython/code.h

@@ -3,6 +3,8 @@
 #endif
 
 typedef uint16_t _Py_CODEUNIT;
+// Each oparg must fit in the second half of _Py_CODEUNIT, hence 8 bits.
+#define _Py_MAX_OPARG 255
 
 #ifdef WORDS_BIGENDIAN
 #  define _Py_OPCODE(word) ((word) >> 8)
@@ -16,6 +18,11 @@ typedef uint16_t _Py_CODEUNIT;
 
 typedef struct _PyOpcache _PyOpcache;
 
+
+// These are duplicated from pycore_code.h.
+typedef unsigned char _PyLocalsPlusKind;
+typedef _PyLocalsPlusKind *_PyLocalsPlusKinds;
+
 /* Bytecode object */
 struct PyCodeObject {
     PyObject_HEAD
@@ -47,7 +54,9 @@ struct PyCodeObject {
     // The hottest fields (in the eval loop) are grouped here at the top.
     PyObject *co_consts;        /* list (constants used) */
     PyObject *co_names;         /* list of strings (names used) */
-    _Py_CODEUNIT *co_firstinstr; /* Pointer to first instruction, used for quickening */
+    _Py_CODEUNIT *co_firstinstr; /* Pointer to first instruction, used for quickening.
+                                    Unlike the other "hot" fields, this one is
+                                    actually derived from co_code. */
     PyObject *co_exceptiontable; /* Byte string encoding exception handling table */
     int co_flags;               /* CO_..., see below */
     int co_warmup;              /* Warmup counter for quickening */
@@ -59,9 +68,8 @@ struct PyCodeObject {
     int co_stacksize;           /* #entries needed for evaluation stack */
     int co_firstlineno;         /* first source line number */
     PyObject *co_code;          /* instruction opcodes */
-    PyObject *co_varnames;      /* tuple of strings (local variable names) */
-    PyObject *co_cellvars;      /* tuple of strings (cell variable names) */
-    PyObject *co_freevars;      /* tuple of strings (free variable names) */
+    PyObject *co_localsplusnames;  /* tuple mapping offsets to names */
+    _PyLocalsPlusKinds co_localspluskinds; /* array mapping to local kinds */
     PyObject *co_filename;      /* unicode (where it was loaded from) */
     PyObject *co_name;          /* unicode (name, for reference) */
     PyObject *co_linetable;     /* string (encoding addr<->lineno mapping) See
@@ -70,11 +78,15 @@ struct PyCodeObject {
     /* These fields are set with computed values on new code objects. */
 
     int *co_cell2arg;           /* Maps cell vars which are arguments. */
-    // These are redundant but offer some performance benefit.
+    // redundant values (derived from co_localsplusnames and co_localspluskinds)
     int co_nlocalsplus;         /* number of local + cell + free variables */
     int co_nlocals;             /* number of local variables */
     int co_ncellvars;           /* number of cell variables */
     int co_nfreevars;           /* number of free variables */
+    // lazily-computed values
+    PyObject *co_varnames;      /* tuple of strings (local variable names) */
+    PyObject *co_cellvars;      /* tuple of strings (cell variable names) */
+    PyObject *co_freevars;      /* tuple of strings (free variable names) */
 
     /* The remaining fields are zeroed out on new code objects. */
 
@@ -152,7 +164,7 @@ struct PyCodeObject {
 PyAPI_DATA(PyTypeObject) PyCode_Type;
 
 #define PyCode_Check(op) Py_IS_TYPE(op, &PyCode_Type)
-#define PyCode_GetNumFree(op) (PyTuple_GET_SIZE((op)->co_freevars))
+#define PyCode_GetNumFree(op) ((op)->co_nfreevars)
 
 /* Public interface */
 PyAPI_FUNC(PyCodeObject *) PyCode_New(

Include/internal/pycore_code.h

@@ -150,6 +150,58 @@ int _Py_Quicken(PyCodeObject *code);
 
 extern Py_ssize_t _Py_QuickenedCount;
 
+
+/* "Locals plus" for a code object is the set of locals + cell vars +
+ * free vars.  This relates to variable names as well as offsets into
+ * the "fast locals" storage array of execution frames.  The compiler
+ * builds the list of names, their offsets, and the corresponding
+ * kind of local.
+ *
+ * Those kinds represent the source of the initial value and the
+ * variable's scope (as related to closures).  A "local" is an
+ * argument or other variable defined in the current scope.  A "free"
+ * variable is one that is defined in an outer scope and comes from
+ * the function's closure.  A "cell" variable is a local that escapes
+ * into an inner function as part of a closure, and thus must be
+ * wrapped in a cell.  Any "local" can also be a "cell", but the
+ * "free" kind is mutually exclusive with both.
+ */
+
+// We would use an enum if C let us specify the storage type.
+typedef unsigned char _PyLocalsPlusKind;
+/* Note that these all fit within _PyLocalsPlusKind, as do combinations. */
+// Later, we will use the smaller numbers to differentiate the different
+// kinds of locals (e.g. pos-only arg, varkwargs, local-only).
+#define CO_FAST_LOCAL   0x20
+#define CO_FAST_CELL    0x40
+#define CO_FAST_FREE    0x80
+
+typedef _PyLocalsPlusKind *_PyLocalsPlusKinds;
+
+static inline int
+_PyCode_InitLocalsPlusKinds(int num, _PyLocalsPlusKinds *pkinds)
+{
+    if (num == 0) {
+        *pkinds = NULL;
+        return 0;
+    }
+    _PyLocalsPlusKinds kinds = PyMem_NEW(_PyLocalsPlusKind, num);
+    if (kinds == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    *pkinds = kinds;
+    return 0;
+}
+
+static inline void
+_PyCode_ClearLocalsPlusKinds(_PyLocalsPlusKinds kinds)
+{
+    if (kinds != NULL) {
+        PyMem_Free(kinds);
+    }
+}
+
 struct _PyCodeConstructor {
     /* metadata */
     PyObject *filename;
@@ -166,13 +218,13 @@ struct _PyCodeConstructor {
     PyObject *names;
 
     /* mapping frame offsets to information */
-    PyObject *varnames;
-    PyObject *cellvars;
-    PyObject *freevars;
+    PyObject *localsplusnames;
+    _PyLocalsPlusKinds localspluskinds;
 
     /* args (within varnames) */
     int argcount;
     int posonlyargcount;
+    // XXX Replace argcount with posorkwargcount (argcount - posonlyargcount).
     int kwonlyargcount;
 
     /* needed to create the frame */
@@ -199,6 +251,11 @@ PyAPI_FUNC(PyCodeObject *) _PyCode_New(struct _PyCodeConstructor *);
 
 int _PyCode_InitOpcache(PyCodeObject *co);
 
+/* Getters for internal PyCodeObject data. */
+PyAPI_FUNC(PyObject *) _PyCode_GetVarnames(PyCodeObject *);
+PyAPI_FUNC(PyObject *) _PyCode_GetCellvars(PyCodeObject *);
+PyAPI_FUNC(PyObject *) _PyCode_GetFreevars(PyCodeObject *);
+
 
 #ifdef __cplusplus
 }

Lib/ctypes/test/test_values.py

@@ -80,9 +80,9 @@ class struct_frozen(Structure):
                 continue
             items.append((entry.name.decode("ascii"), entry.size))
 
-        expected = [("__hello__", 138),
-                    ("__phello__", -138),
-                    ("__phello__.spam", 138),
+        expected = [("__hello__", 128),
+                    ("__phello__", -128),
+                    ("__phello__.spam", 128),
                     ]
         self.assertEqual(items, expected, "PyImport_FrozenModules example "
             "in Doc/library/ctypes.rst may be out of date")

Lib/dis.py

@@ -273,15 +273,15 @@ def get_instructions(x, *, first_line=None):
     the disassembled code object.
     """
     co = _get_code_object(x)
-    cell_names = co.co_cellvars + co.co_freevars
     linestarts = dict(findlinestarts(co))
     if first_line is not None:
         line_offset = first_line - co.co_firstlineno
     else:
         line_offset = 0
-    return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
-                                   co.co_consts, cell_names, linestarts,
-                                   line_offset)
+    return _get_instructions_bytes(co.co_code,
+                                   co._varname_from_oparg,
+                                   co.co_names, co.co_consts,
+                                   linestarts, line_offset)
 
 def _get_const_info(const_index, const_list):
     """Helper to get optional details about const references
@@ -295,16 +295,16 @@ def _get_const_info(const_index, const_list):
         argval = const_list[const_index]
     return argval, repr(argval)
 
-def _get_name_info(name_index, name_list):
+def _get_name_info(name_index, get_name, **extrainfo):
     """Helper to get optional details about named references
 
        Returns the dereferenced name as both value and repr if the name
        list is defined.
        Otherwise returns the name index and its repr().
     """
     argval = name_index
-    if name_list is not None:
-        argval = name_list[name_index]
+    if get_name is not None:
+        argval = get_name(name_index, **extrainfo)
         argrepr = argval
     else:
         argrepr = repr(argval)
@@ -336,8 +336,10 @@ def parse_exception_table(code):
     except StopIteration:
         return entries
 
-def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
-                      cells=None, linestarts=None, line_offset=0, exception_entries=()):
+def _get_instructions_bytes(code, varname_from_oparg=None,
+                            names=None, constants=None,
+                            linestarts=None, line_offset=0,
+                            exception_entries=()):
     """Iterate over the instructions in a bytecode string.
 
     Generates a sequence of Instruction namedtuples giving the details of each
@@ -346,6 +348,7 @@ def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
     arguments.
 
     """
+    get_name = None if names is None else names.__getitem__
     labels = set(findlabels(code))
     for start, end, target, _, _ in exception_entries:
         for i in range(start, end):
@@ -368,20 +371,18 @@ def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
             if op in hasconst:
                 argval, argrepr = _get_const_info(arg, constants)
             elif op in hasname:
-                argval, argrepr = _get_name_info(arg, names)
+                argval, argrepr = _get_name_info(arg, get_name)
             elif op in hasjabs:
                 argval = arg*2
                 argrepr = "to " + repr(argval)
             elif op in hasjrel:
                 argval = offset + 2 + arg*2
                 argrepr = "to " + repr(argval)
-            elif op in haslocal:
-                argval, argrepr = _get_name_info(arg, varnames)
+            elif op in haslocal or op in hasfree:
+                argval, argrepr = _get_name_info(arg, varname_from_oparg)
             elif op in hascompare:
                 argval = cmp_op[arg]
                 argrepr = argval
-            elif op in hasfree:
-                argval, argrepr = _get_name_info(arg, cells)
             elif op == FORMAT_VALUE:
                 argval, argrepr = FORMAT_VALUE_CONVERTERS[arg & 0x3]
                 argval = (argval, bool(arg & 0x4))
@@ -398,11 +399,11 @@ def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
 
 def disassemble(co, lasti=-1, *, file=None):
     """Disassemble a code object."""
-    cell_names = co.co_cellvars + co.co_freevars
     linestarts = dict(findlinestarts(co))
     exception_entries = parse_exception_table(co)
-    _disassemble_bytes(co.co_code, lasti, co.co_varnames, co.co_names,
-                       co.co_consts, cell_names, linestarts, file=file,
+    _disassemble_bytes(co.co_code, lasti,
+                       co._varname_from_oparg,
+                       co.co_names, co.co_consts, linestarts, file=file,
                        exception_entries=exception_entries)
 
 def _disassemble_recursive(co, *, file=None, depth=None):
@@ -416,8 +417,8 @@ def _disassemble_recursive(co, *, file=None, depth=None):
                 print("Disassembly of %r:" % (x,), file=file)
                 _disassemble_recursive(x, file=file, depth=depth)
 
-def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
-                       constants=None, cells=None, linestarts=None,
+def _disassemble_bytes(code, lasti=-1, varname_from_oparg=None,
+                       names=None, constants=None, linestarts=None,
                        *, file=None, line_offset=0, exception_entries=()):
     # Omit the line number column entirely if we have no line number info
     show_lineno = bool(linestarts)
@@ -434,8 +435,8 @@ def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
         offset_width = len(str(maxoffset))
     else:
         offset_width = 4
-    for instr in _get_instructions_bytes(code, varnames, names,
-                                         constants, cells, linestarts,
+    for instr in _get_instructions_bytes(code, varname_from_oparg, names,
+                                         constants, linestarts,
                                          line_offset=line_offset, exception_entries=exception_entries):
         new_source_line = (show_lineno and
                            instr.starts_line is not None and
@@ -517,16 +518,16 @@ def __init__(self, x, *, first_line=None, current_offset=None):
         else:
             self.first_line = first_line
             self._line_offset = first_line - co.co_firstlineno
-        self._cell_names = co.co_cellvars + co.co_freevars
         self._linestarts = dict(findlinestarts(co))
         self._original_object = x
         self.current_offset = current_offset
         self.exception_entries = parse_exception_table(co)
 
     def __iter__(self):
         co = self.codeobj
-        return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
-                                       co.co_consts, self._cell_names,
+        return _get_instructions_bytes(co.co_code,
+                                       co._varname_from_oparg,
+                                       co.co_names, co.co_consts,
                                        self._linestarts,
                                        line_offset=self._line_offset,
                                        exception_entries=self.exception_entries)
@@ -554,9 +555,9 @@ def dis(self):
         else:
             offset = -1
         with io.StringIO() as output:
-            _disassemble_bytes(co.co_code, varnames=co.co_varnames,
+            _disassemble_bytes(co.co_code,
+                               varname_from_oparg=co._varname_from_oparg,
                                names=co.co_names, constants=co.co_consts,
-                               cells=self._cell_names,
                                linestarts=self._linestarts,
                                line_offset=self._line_offset,
                                file=output,