bytecode instead of on these mechanical issues. |
bytecode instead of on these mechanical issues. |
|
|
In addition to a low-level opcode-oriented API for directly generating specific |
In addition to a low-level opcode-oriented API for directly generating specific |
bytecodes, this module also offers an extensible mini-AST framework for |
Python bytecodes, this module also offers an extensible mini-AST framework for |
generating code from high-level specifications. This framework does most of |
generating code from high-level specifications. This framework does most of |
the work needed to transform tree-like structures into linear bytecode |
the work needed to transform tree-like structures into linear bytecode |
instructions, and includes the ability to do compile-time constant folding. |
instructions, and includes the ability to do compile-time constant folding. |
|
|
|
Please see the `BytecodeAssembler reference manual`_ for more details. |
|
|
|
.. _BytecodeAssembler reference manual: http://peak.telecommunity.com/DevCenter/BytecodeAssembler#toc |
|
|
|
|
|
Changes since version 0.5.1: |
|
|
|
* Initial support for Python 2.7's new opcodes and semantics changes, mostly |
|
by emulating older versions' behavior with macros. (0.5.2 is really just |
|
a quick-fix release to allow packages using BytecodeAssembler to run on 2.7 |
|
without having to change any of their code generation; future releases will |
|
provide proper support for the new and changed opcodes, as well as a test |
|
suite that doesn't show spurious differences in the disassembly listings |
|
under Python 2.7.) |
|
|
|
Changes since version 0.5: |
|
|
|
* Fix incorrect stack size calculation for ``MAKE_CLOSURE`` on Python 2.5+ |
|
|
|
Changes since version 0.3: |
|
|
|
* New node types: |
|
|
|
* ``For(iterable, assign, body)`` -- define a "for" loop over `iterable` |
|
|
|
* ``UnpackSequence(nodes)`` -- unpacks a sequence that's ``len(nodes)`` long, |
|
and then generates the given nodes. |
|
|
|
* ``LocalAssign(name)`` -- issues a ``STORE_FAST``, ``STORE_DEREF`` or |
|
``STORE_LOCAL`` as appropriate for the given name. |
|
|
|
* ``Function(body, name='<lambda>', args=(), var=None, kw=None, defaults=())`` |
|
-- creates a nested function from `body` and puts it on the stack. |
|
|
|
* ``If(cond, then_, else_=Pass)`` -- "if" statement analogue |
|
|
|
* ``ListComp(body)`` and ``LCAppend(value)`` -- implement list comprehensions |
|
|
|
* ``YieldStmt(value)`` -- generates a ``YIELD_VALUE`` (plus a ``POP_TOP`` in |
|
Python 2.5+) |
|
|
|
* ``Code`` objects are now iterable, yielding ``(offset, op, arg)`` triples, |
|
where `op` is numeric and `arg` is either numeric or ``None``. |
|
|
|
* ``Code`` objects' ``.code()`` method can now take a "parent" ``Code`` object, |
|
to link the child code's free variables to cell variables in the parent. |
|
|
|
* Added ``Code.from_spec()`` classmethod, that initializes a code object from a |
|
name and argument spec. |
|
|
|
* ``Code`` objects now have a ``.nested(name, args, var, kw)`` method, that |
|
creates a child code object with the same ``co_filename`` and the supplied |
|
name/arg spec. |
|
|
|
* Fixed incorrect stack tracking for the ``FOR_ITER`` and ``YIELD_VALUE`` |
|
opcodes |
|
|
|
* Ensure that ``CO_GENERATOR`` flag is set if ``YIELD_VALUE`` opcode is used |
|
|
|
* Change tests so that Python 2.3's broken line number handling in ``dis.dis`` |
|
and constant-folding optimizer don't generate spurious failures in this |
|
package's test suite. |
|
|
|
|
Changes since version 0.2: |
Changes since version 0.2: |
|
|
|
* Added ``Suite``, ``TryExcept``, and ``TryFinally`` node types |
|
|
|
* Added a ``Getattr`` node type that does static or dynamic attribute access |
|
and constant folding |
|
|
|
* Fixed ``code.from_function()`` not copying the ``co_filename`` attribute when |
|
``copy_lineno`` was specified. |
|
|
* The ``repr()`` of AST nodes doesn't include a trailing comma for 1-argument |
* The ``repr()`` of AST nodes doesn't include a trailing comma for 1-argument |
node types any more. |
node types any more. |
|
|
* Added a ``Pass`` symbol that generates no code, and a ``Compare()`` node type |
* Added a ``Pass`` symbol that generates no code, a ``Compare()`` node type |
that does n-way comparisons. |
that does n-way comparisons, and ``And()`` and ``Or()`` node types for doing |
|
logical operations. |
|
|
* The ``COMPARE_OP()`` method now accepts operator strings like ``"<="``, |
* The ``COMPARE_OP()`` method now accepts operator strings like ``"<="``, |
``"not in"``, ``"exception match"``, and so on, as well as numeric opcodes. |
``"not in"``, ``"exception match"``, and so on, as well as numeric opcodes. |
strings accepted (in the ``cmp_op`` tuple). ``"<>"`` is also accepted as an |
strings accepted (in the ``cmp_op`` tuple). ``"<>"`` is also accepted as an |
alias for ``"!="``. |
alias for ``"!="``. |
|
|
|
* Added code to verify that forward jump offsets don't exceed a 64KB span, and |
|
support absolute backward jumps to locations >64KB. |
|
|
Changes since version 0.1: |
Changes since version 0.1: |
|
|
* Constant handling has been fixed so that it doesn't confuse equal values of |
* Constant handling has been fixed so that it doesn't confuse equal values of |
* Various bug fixes |
* Various bug fixes |
|
|
There are a few features that aren't tested yet, and not all opcodes may be |
There are a few features that aren't tested yet, and not all opcodes may be |
fully supported. Notably, the following features are still NOT reliably |
fully supported. Also note the following limitations: |
supported yet: |
|
|
|
* Wide jump addressing (for generated bytecode>64K in size) |
* Jumps to as-yet-undefined labels cannot span a distance greater than 65,535 |
|
bytes. |
|
|
* The ``dis()`` module in Python 2.3 has a bug that makes it show incorrect |
* The ``dis()`` function in Python 2.3 has a bug that makes it show incorrect |
line numbers when the difference between two adjacent line numbers is |
line numbers when the difference between two adjacent line numbers is |
greater than 255. This causes two shallow failures in the current test |
greater than 255. (To work around this, the test_suite uses a later version |
suite when it's run under Python 2.3. |
of ``dis()``, but do note that it may affect your own tests if you use |
|
``dis()`` with Python 2.3 and use widely separated line numbers.) |
|
|
If you find any other issues, please let me know. |
If you find any other issues, please let me know. |
|
|
Questions and discussion regarding this software should be directed to the |
Questions and discussion regarding this software should be directed to the |
`PEAK Mailing List <http://www.eby-sarna.com/mailman/listinfo/peak>`_. |
`PEAK Mailing List <http://www.eby-sarna.com/mailman/listinfo/peak>`_. |
|
|
|
.. _toc: |
.. contents:: **Table of Contents** |
.. contents:: **Table of Contents** |
|
|
|
|
>>> f() |
>>> f() |
42 |
42 |
|
|
|
Finally, code objects are also iterable, yielding ``(offset, opcode, arg)`` |
|
tuples, where `arg` is ``None`` for opcodes with no arguments, and an integer |
|
otherwise:: |
|
|
|
>>> import peak.util.assembler as op |
|
>>> list(c) == [ |
|
... (0, op.LOAD_CONST, 1), |
|
... (3, op.RETURN_VALUE, None) |
|
... ] |
|
True |
|
|
|
This can be useful for testing or otherwise inspecting code you've generated. |
|
|
|
|
|
Symbolic Disassembler |
|
===================== |
|
|
|
Python's built-in disassembler can be verbose and hard to read when inspecting |
|
complex generated code -- usually you don't care about bytecode offsets or |
|
line numbers as much as you care about labels, for example. |
|
|
|
So, BytecodeAssembler provides its own, simplified disassembler, which we'll |
|
be using for more complex listings in this manual:: |
|
|
|
>>> from peak.util.assembler import dump |
|
|
|
Some sample output, that also showcases some of BytecodeAssembler's |
|
`High-Level Code Generation`_ features:: |
|
|
|
>>> c = Code() |
|
>>> from peak.util.assembler import Compare, Local |
|
>>> c.return_(Compare(Local('a'), [('<', Local('b')), ('<', Local('c'))])) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (a) |
|
LOAD_FAST 1 (b) |
|
DUP_TOP |
|
ROT_THREE |
|
COMPARE_OP 0 (<) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_FAST 2 (c) |
|
COMPARE_OP 0 (<) |
|
JUMP_FORWARD L2 |
|
L1: ROT_TWO |
|
POP_TOP |
|
L2: RETURN_VALUE |
|
|
|
As you can see, the line numbers and bytecode offsets have been dropped, |
|
making it esier to see where the jumps go. (This also makes doctests more |
|
robust against Python version changes, as ``dump()`` has some extra code to |
|
make conditional jumps appear consistent across the major changes that were |
|
made to conditional jump instructions between Python 2.6 and 2.7.) |
|
|
|
|
Opcodes and Arguments |
Opcodes and Arguments |
===================== |
===================== |
>>> c.POP_TOP() |
>>> c.POP_TOP() |
>>> c.JUMP_ABSOLUTE(where) # now jump back to it |
>>> c.JUMP_ABSOLUTE(where) # now jump back to it |
|
|
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (42) |
LOAD_CONST 1 (42) |
>> 3 DUP_TOP |
L1: DUP_TOP |
4 POP_TOP |
POP_TOP |
5 JUMP_ABSOLUTE 3 |
JUMP_ABSOLUTE L1 |
|
|
But if you are jumping *forward*, you will need to call the jump or setup |
But if you are jumping *forward*, you will need to call the jump or setup |
method without any arguments. The return value will be a "forward reference" |
method without any arguments. The return value will be a "forward reference" |
>>> c.LOAD_CONST(23) |
>>> c.LOAD_CONST(23) |
>>> c.RETURN_VALUE() |
>>> c.RETURN_VALUE() |
|
|
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (99) |
LOAD_CONST 1 (99) |
3 JUMP_IF_TRUE 4 (to 10) |
JUMP_IF_TRUE L1 |
6 LOAD_CONST 2 (42) |
LOAD_CONST 2 (42) |
9 POP_TOP |
POP_TOP |
>> 10 LOAD_CONST 3 (23) |
L1: LOAD_CONST 3 (23) |
13 RETURN_VALUE |
RETURN_VALUE |
|
|
>>> eval(c.code()) |
>>> eval(c.code()) |
23 |
23 |
>>> c = Code() |
>>> c = Code() |
>>> c.co_cellvars = ('a','b') |
>>> c.co_cellvars = ('a','b') |
|
|
|
>>> import sys |
>>> c.LOAD_CLOSURE('a') |
>>> c.LOAD_CLOSURE('a') |
>>> c.LOAD_CLOSURE('b') |
>>> c.LOAD_CLOSURE('b') |
|
>>> if sys.version>='2.5': |
|
... c.BUILD_TUPLE(2) # In Python 2.5+, free vars must be in a tuple |
>>> c.LOAD_CONST(None) # in real code, this'd be a Python code constant |
>>> c.LOAD_CONST(None) # in real code, this'd be a Python code constant |
>>> c.MAKE_CLOSURE(0,2) # no defaults, 2 free vars in the new function |
>>> c.MAKE_CLOSURE(0,2) # no defaults, 2 free vars in the new function |
|
|
|
>>> c.stack_size # This will be 1, no matter what Python version |
|
1 |
|
|
The ``COMPARE_OP`` method takes an argument which can be a valid comparison |
The ``COMPARE_OP`` method takes an argument which can be a valid comparison |
integer constant, or a string containing a Python operator, e.g.:: |
integer constant, or a string containing a Python operator, e.g.:: |
|
|
6 LOAD_CONST 3 (1.0) |
6 LOAD_CONST 3 (1.0) |
9 LOAD_CONST 4 (1L) |
9 LOAD_CONST 4 (1L) |
|
|
|
|
Simple Containers |
Simple Containers |
----------------- |
----------------- |
|
|
False |
False |
|
|
|
|
|
``Suite`` and ``Pass`` |
|
---------------------- |
|
|
|
On occasion, it's helpful to be able to group a sequence of opcodes, |
|
expressions, or statements together, to be passed as an argument to other node |
|
types. The ``Suite`` node type accomplishes this:: |
|
|
|
>>> from peak.util.assembler import Suite, Pass |
|
|
|
>>> c = Code() |
|
>>> c.return_(Suite([Const(42), Code.DUP_TOP, Code.POP_TOP])) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 DUP_TOP |
|
4 POP_TOP |
|
5 RETURN_VALUE |
|
|
|
And ``Pass`` is a shortcut for an empty ``Suite``, that generates nothing:: |
|
|
|
>>> Suite([]) |
|
Pass |
|
|
|
>>> c = Code() |
|
>>> c(Pass) |
|
>>> c.return_(None) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 0 (None) |
|
3 RETURN_VALUE |
|
|
|
|
Local and Global Names |
Local and Global Names |
---------------------- |
---------------------- |
|
|
0 0 LOAD_FAST 0 (x) |
0 0 LOAD_FAST 0 (x) |
3 LOAD_GLOBAL 0 (y) |
3 LOAD_GLOBAL 0 (y) |
|
|
|
|
As with simple constants and ``Const`` wrappers, these objects can be used to |
As with simple constants and ``Const`` wrappers, these objects can be used to |
construct more complex expressions, like ``{a:(b,c)}``:: |
construct more complex expressions, like ``{a:(b,c)}``:: |
|
|
16 ROT_THREE |
16 ROT_THREE |
17 STORE_SUBSCR |
17 STORE_SUBSCR |
|
|
|
The ``LocalAssign`` node type takes a name, and stores a value in a local |
|
variable:: |
|
|
|
>>> from peak.util.assembler import LocalAssign |
|
>>> c = Code() |
|
>>> c(42, LocalAssign('x')) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 0 (x) |
|
|
If the code object is not using "fast locals" (i.e. ``CO_OPTIMIZED`` isn't |
If the code object is not using "fast locals" (i.e. ``CO_OPTIMIZED`` isn't |
set), local variables will be dereferenced using ``LOAD_NAME`` instead of |
set), local variables will be referenced using ``LOAD_NAME`` and ``STORE_NAME`` |
``LOAD_FAST``, and if the referenced local name is a "cell" or "free" |
instead of ``LOAD_FAST`` and ``STORE_FAST``, and if the referenced local name |
variable, ``LOAD_DEREF`` is used instead:: |
is a "cell" or "free" variable, ``LOAD_DEREF`` and ``STORE_DEREF`` are used |
|
instead:: |
|
|
>>> from peak.util.assembler import CO_OPTIMIZED |
>>> from peak.util.assembler import CO_OPTIMIZED |
>>> c = Code() |
>>> c = Code() |
>>> c.co_cellvars = ('y',) |
>>> c.co_cellvars = ('y',) |
>>> c.co_freevars = ('z',) |
>>> c.co_freevars = ('z',) |
>>> c( Local('x'), Local('y'), Local('z') ) |
>>> c( Local('x'), Local('y'), Local('z') ) |
|
>>> c( LocalAssign('x'), LocalAssign('y'), LocalAssign('z') ) |
>>> dis(c.code()) |
>>> dis(c.code()) |
0 0 LOAD_NAME 0 (x) |
0 0 LOAD_NAME 0 (x) |
3 LOAD_DEREF 0 (y) |
3 LOAD_DEREF 0 (y) |
6 LOAD_DEREF 1 (z) |
6 LOAD_DEREF 1 (z) |
|
9 STORE_NAME 0 (x) |
|
12 STORE_DEREF 0 (y) |
|
15 STORE_DEREF 1 (z) |
|
|
|
|
|
Obtaining Attributes |
|
-------------------- |
|
|
|
The ``Getattr`` node type takes an expression and an attribute name. The |
|
attribute name can be a constant string, in which case a ``LOAD_ATTR`` opcode |
|
is used, and constant folding is done if possible:: |
|
|
|
>>> from peak.util.assembler import Getattr |
|
|
|
>>> c = Code() |
|
>>> c(Getattr(Local('x'), '__class__')) |
|
>>> dis(c.code()) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_ATTR 0 (__class__) |
|
|
|
|
|
>>> Getattr(Const(object), '__class__') # const expression, const result |
|
Const(<type 'type'>) |
|
|
|
Or the attribute name can be an expression, in which case a ``getattr()`` call |
|
is compiled instead:: |
|
|
|
>>> c = Code() |
|
>>> c(Getattr(Local('x'), Local('y'))) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (<built-in function getattr>) |
|
3 LOAD_FAST 0 (x) |
|
6 LOAD_FAST 1 (y) |
|
9 CALL_FUNCTION 2 |
|
|
|
|
Calling Functions and Methods |
Calling Functions and Methods |
3 RETURN_VALUE |
3 RETURN_VALUE |
|
|
|
|
|
``If`` Conditions |
|
----------------- |
|
|
|
The ``If()`` node type generates conditional code, roughly equivalent to a |
|
Python if/else statement:: |
|
|
|
>>> from peak.util.assembler import If |
|
>>> c = Code() |
|
>>> c( If(Local('a'), Return(42), Return(55)) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (a) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_CONST 1 (42) |
|
RETURN_VALUE |
|
L1: POP_TOP |
|
LOAD_CONST 2 (55) |
|
RETURN_VALUE |
|
|
|
However, it can also be used like a Python 2.5+ conditional expression |
|
(regardless of the targeted Python version):: |
|
|
|
>>> c = Code() |
|
>>> c( Return(If(Local('a'), 42, 55)) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (a) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_CONST 1 (42) |
|
JUMP_FORWARD L2 |
|
L1: POP_TOP |
|
LOAD_CONST 2 (55) |
|
L2: RETURN_VALUE |
|
|
|
|
|
Note that ``If()`` does *not* do constant-folding on its condition; even if the |
|
condition is a constant, it will be tested at runtime. This avoids issues with |
|
using mutable constants, e.g.:: |
|
|
|
>>> c = Code() |
|
>>> c(If(Const([]), 42, 55)) |
|
>>> dump(c.code()) |
|
LOAD_CONST 1 ([]) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_CONST 2 (42) |
|
JUMP_FORWARD L2 |
|
L1: POP_TOP |
|
LOAD_CONST 3 (55) |
|
|
|
|
Labels and Jump Targets |
Labels and Jump Targets |
----------------------- |
----------------------- |
|
|
>>> c.LOAD_CONST(99) |
>>> c.LOAD_CONST(99) |
>>> forward = c.JUMP_IF_FALSE() |
>>> forward = c.JUMP_IF_FALSE() |
>>> c( 1, Code.POP_TOP, forward, Return(3) ) |
>>> c( 1, Code.POP_TOP, forward, Return(3) ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (99) |
LOAD_CONST 1 (99) |
3 JUMP_IF_FALSE 4 (to 10) |
JUMP_IF_FALSE L1 |
6 LOAD_CONST 2 (1) |
LOAD_CONST 2 (1) |
9 POP_TOP |
POP_TOP |
>> 10 LOAD_CONST 3 (3) |
L1: LOAD_CONST 3 (3) |
13 RETURN_VALUE |
RETURN_VALUE |
|
|
However, there's an easier way to do the same thing, using ``Label`` objects:: |
However, there's an easier way to do the same thing, using ``Label`` objects:: |
|
|
>>> skip = Label() |
>>> skip = Label() |
|
|
>>> c(99, skip.JUMP_IF_FALSE, 1, Code.POP_TOP, skip, Return(3)) |
>>> c(99, skip.JUMP_IF_FALSE, 1, Code.POP_TOP, skip, Return(3)) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (99) |
LOAD_CONST 1 (99) |
3 JUMP_IF_FALSE 4 (to 10) |
JUMP_IF_FALSE L1 |
6 LOAD_CONST 2 (1) |
LOAD_CONST 2 (1) |
9 POP_TOP |
POP_TOP |
>> 10 LOAD_CONST 3 (3) |
L1: LOAD_CONST 3 (3) |
13 RETURN_VALUE |
RETURN_VALUE |
|
|
This approach has the advantage of being easy to use in complex trees. |
This approach has the advantage of being easy to use in complex trees. |
``Label`` objects have attributes corresponding to every opcode that uses a |
``Label`` objects have attributes corresponding to every opcode that uses a |
|
|
>>> c = Code() |
>>> c = Code() |
>>> c.return_(Compare(Local('a'), [('<', Local('b')), ('<', Local('c'))])) |
>>> c.return_(Compare(Local('a'), [('<', Local('b')), ('<', Local('c'))])) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_FAST 0 (a) |
LOAD_FAST 0 (a) |
3 LOAD_FAST 1 (b) |
LOAD_FAST 1 (b) |
6 DUP_TOP |
DUP_TOP |
7 ROT_THREE |
ROT_THREE |
8 COMPARE_OP 0 (<) |
COMPARE_OP 0 (<) |
11 JUMP_IF_FALSE 10 (to 24) |
JUMP_IF_FALSE L1 |
14 POP_TOP |
POP_TOP |
15 LOAD_FAST 2 (c) |
LOAD_FAST 2 (c) |
18 COMPARE_OP 0 (<) |
COMPARE_OP 0 (<) |
21 JUMP_FORWARD 2 (to 26) |
JUMP_FORWARD L2 |
>> 24 ROT_TWO |
L1: ROT_TWO |
25 POP_TOP |
POP_TOP |
>> 26 RETURN_VALUE |
L2: RETURN_VALUE |
|
|
And a four-way (``a<b>c!=d``):: |
And a four-way (``a<b>c!=d``):: |
|
|
... ('<', Local('b')), ('>', Local('c')), ('!=', Local('d')) |
... ('<', Local('b')), ('>', Local('c')), ('!=', Local('d')) |
... ]) |
... ]) |
... ) |
... ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_FAST 0 (a) |
LOAD_FAST 0 (a) |
3 LOAD_FAST 1 (b) |
LOAD_FAST 1 (b) |
6 DUP_TOP |
DUP_TOP |
7 ROT_THREE |
ROT_THREE |
8 COMPARE_OP 0 (<) |
COMPARE_OP 0 (<) |
11 JUMP_IF_FALSE 22 (to 36) |
JUMP_IF_FALSE L1 |
14 POP_TOP |
POP_TOP |
15 LOAD_FAST 2 (c) |
LOAD_FAST 2 (c) |
18 DUP_TOP |
DUP_TOP |
19 ROT_THREE |
ROT_THREE |
20 COMPARE_OP 4 (>) |
COMPARE_OP 4 (>) |
23 JUMP_IF_FALSE 10 (to 36) |
JUMP_IF_FALSE L1 |
26 POP_TOP |
POP_TOP |
27 LOAD_FAST 3 (d) |
LOAD_FAST 3 (d) |
30 COMPARE_OP 3 (!=) |
COMPARE_OP 3 (!=) |
33 JUMP_FORWARD 2 (to 38) |
JUMP_FORWARD L2 |
>> 36 ROT_TWO |
L1: ROT_TWO |
37 POP_TOP |
POP_TOP |
>> 38 RETURN_VALUE |
L2: RETURN_VALUE |
|
|
|
|
|
Sequence Unpacking |
|
------------------ |
|
|
|
The ``UnpackSequence`` node type takes a sequence of code generation targets, |
|
and generates an ``UNPACK_SEQUENCE`` of the correct length, followed by the |
|
targets:: |
|
|
|
>>> from peak.util.assembler import UnpackSequence |
|
>>> c = Code() |
|
>>> c((1,2), UnpackSequence([LocalAssign('x'), LocalAssign('y')])) |
|
>>> dis(c.code()) # x, y = 1, 2 |
|
0 0 LOAD_CONST 1 (1) |
|
3 LOAD_CONST 2 (2) |
|
6 BUILD_TUPLE 2 |
|
9 UNPACK_SEQUENCE 2 |
|
12 STORE_FAST 0 (x) |
|
15 STORE_FAST 1 (y) |
|
|
|
|
|
Yield Statements |
|
---------------- |
|
|
|
The ``YieldStmt`` node type generates the necessary opcode(s) for a ``yield`` |
|
statement, based on the target Python version. (In Python 2.5+, a ``POP_TOP`` |
|
must be generated after a ``YIELD_VALUE`` in order to create a yield statement, |
|
as opposed to a yield expression.) It also sets the code flags needed to make |
|
the resulting code object a generator:: |
|
|
|
>>> from peak.util.assembler import YieldStmt |
|
>>> c = Code() |
|
>>> c(YieldStmt(1), YieldStmt(2), Return(None)) |
|
>>> list(eval(c.code())) |
|
[1, 2] |
|
|
|
|
|
|
Constant Detection and Folding |
Constant Detection and Folding |
``globals()``, in other words. |
``globals()``, in other words. |
|
|
|
|
|
Logical And/Or |
|
-------------- |
|
|
|
You can evaluate logical and/or expressions using the ``And`` and ``Or`` node |
|
types:: |
|
|
|
>>> from peak.util.assembler import And, Or |
|
|
|
>>> c = Code() |
|
>>> c.return_( And([Local('x'), Local('y')]) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (x) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_FAST 1 (y) |
|
L1: RETURN_VALUE |
|
|
|
>>> c = Code() |
|
>>> c.return_( Or([Local('x'), Local('y')]) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (x) |
|
JUMP_IF_TRUE L1 |
|
POP_TOP |
|
LOAD_FAST 1 (y) |
|
L1: RETURN_VALUE |
|
|
|
|
|
True or false constants are folded automatically, avoiding code generation |
|
for intermediate values that will never be used in the result:: |
|
|
|
>>> c = Code() |
|
>>> c.return_( And([1, 2, Local('y')]) ) |
|
>>> dis(c.code()) |
|
0 0 LOAD_FAST 0 (y) |
|
3 RETURN_VALUE |
|
|
|
>>> c = Code() |
|
>>> c.return_( And([1, 2, Local('y'), 0]) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (y) |
|
JUMP_IF_FALSE L1 |
|
POP_TOP |
|
LOAD_CONST 1 (0) |
|
L1: RETURN_VALUE |
|
|
|
>>> c = Code() |
|
>>> c.return_( Or([1, 2, Local('y')]) ) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (1) |
|
3 RETURN_VALUE |
|
|
|
>>> c = Code() |
|
>>> c.return_( Or([False, Local('y'), 3]) ) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (y) |
|
JUMP_IF_TRUE L1 |
|
POP_TOP |
|
LOAD_CONST 1 (3) |
|
L1: RETURN_VALUE |
|
|
|
|
Custom Code Generation |
Custom Code Generation |
====================== |
====================== |
|
|
|
|
>>> c = Code() |
>>> c = Code() |
>>> c( TryFinally(ExprStmt(1), ExprStmt(2)) ) |
>>> c( TryFinally(ExprStmt(1), ExprStmt(2)) ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_FINALLY 8 (to 11) |
SETUP_FINALLY L1 |
3 LOAD_CONST 1 (1) |
LOAD_CONST 1 (1) |
6 POP_TOP |
POP_TOP |
7 POP_BLOCK |
POP_BLOCK |
8 LOAD_CONST 0 (None) |
LOAD_CONST 0 (None) |
>> 11 LOAD_CONST 2 (2) |
L1: LOAD_CONST 2 (2) |
14 POP_TOP |
POP_TOP |
15 END_FINALLY |
END_FINALLY |
|
|
The ``nodetype()`` decorator is virtually identical to the ``struct()`` |
The ``nodetype()`` decorator is virtually identical to the ``struct()`` |
decorator in the DecoratorTools package, except that it does not support |
decorator in the DecoratorTools package, except that it does not support |
|
|
If you want to incorporate constant-folding into your AST nodes, you can do |
If you want to incorporate constant-folding into your AST nodes, you can do |
so by checking for constant values and folding them at either construction |
so by checking for constant values and folding them at either construction |
or code generation time. For example, this ``And`` node type folds constants |
or code generation time. For example, this ``And`` node type (a simpler |
during code generation, by not generating unnecessary branches when it can |
version of the one included in ``peak.util.assembler``) folds constants during |
|
code generation, by not generating unnecessary branches when it can |
prove which way a branch will go:: |
prove which way a branch will go:: |
|
|
>>> from peak.util.assembler import NotAConstant |
>>> from peak.util.assembler import NotAConstant |
|
|
>>> c = Code() |
>>> c = Code() |
>>> c.return_( And([Local('x'), False, 27]) ) |
>>> c.return_( And([Local('x'), False, 27]) ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_FAST 0 (x) |
LOAD_FAST 0 (x) |
3 JUMP_IF_FALSE 4 (to 10) |
JUMP_IF_FALSE L1 |
6 POP_TOP |
POP_TOP |
7 LOAD_CONST 1 (False) |
LOAD_CONST 1 (False) |
>> 10 RETURN_VALUE |
L1: RETURN_VALUE |
|
|
The above example only folds constants at code generation time, however. You |
The above example only folds constants at code generation time, however. You |
can also do constant folding at AST construction time, using the |
can also do constant folding at AST construction time, using the |
implements its ``fold`` argument and the suppression of folding when |
implements its ``fold`` argument and the suppression of folding when |
the call has no arguments. |
the call has no arguments. |
|
|
|
(By the way, this same ``Getattr`` node type is also available |
|
|
|
|
Setting the Code's Calling Signature |
Setting the Code's Calling Signature |
==================================== |
==================================== |
|
|
>>> import inspect |
>>> import inspect |
|
|
>>> inspect.getargspec(f1) |
>>> tuple(inspect.getargspec(f1)) |
(['a', 'b'], 'c', 'd', None) |
(['a', 'b'], 'c', 'd', None) |
|
|
>>> inspect.getargspec(f2) |
>>> tuple(inspect.getargspec(f2)) |
(['a', 'b'], 'c', 'd', None) |
(['a', 'b'], 'c', 'd', None) |
|
|
Note that these constructors do not copy any actual *code* from the code |
Note that these constructors do not copy any actual *code* from the code |
>>> c1 = Code.from_function(f1, copy_lineno=True) |
>>> c1 = Code.from_function(f1, copy_lineno=True) |
>>> c1.co_firstlineno |
>>> c1.co_firstlineno |
1 |
1 |
|
>>> c1.co_filename is f1.func_code.co_filename |
|
True |
|
|
If you create a ``Code`` instance from a function that has nested positional |
If you create a ``Code`` instance from a function that has nested positional |
arguments, the returned code object will include a prologue to unpack the |
arguments, the returned code object will include a prologue to unpack the |
unpacking process, and is designed so that the ``inspect`` module will |
unpacking process, and is designed so that the ``inspect`` module will |
recognize it as an argument unpacking prologue:: |
recognize it as an argument unpacking prologue:: |
|
|
>>> inspect.getargspec(f3) |
>>> tuple(inspect.getargspec(f3)) |
(['a', ['b', 'c'], ['d', ['e', 'f']]], None, None, None) |
(['a', ['b', 'c'], ['d', ['e', 'f']]], None, None, None) |
|
|
>>> inspect.getargspec(f4) |
>>> tuple(inspect.getargspec(f4)) |
(['a', ['b', 'c'], ['d', ['e', 'f']]], None, None, None) |
(['a', ['b', 'c'], ['d', ['e', 'f']]], None, None, None) |
|
|
|
You can also use the ``from_spec(name='<lambda>', args=(), var=None, kw=None)`` |
|
classmethod to explicitly set a name and argument spec for a new code object:: |
|
|
|
>>> c = Code.from_spec('a', ('b', ('c','d'), 'e'), 'f', 'g') |
|
>>> c.co_name |
|
'a' |
|
|
|
>>> c.co_varnames |
|
['b', '.1', 'e', 'f', 'g', 'c', 'd'] |
|
|
|
>>> c.co_argcount |
|
3 |
|
|
|
>>> tuple(inspect.getargs(c.code())) |
|
(['b', ['c', 'd'], 'e'], 'f', 'g') |
|
|
|
|
Code Attributes |
Code Attributes |
=============== |
=============== |
42 |
42 |
|
|
>>> import inspect |
>>> import inspect |
>>> inspect.getargspec(f) |
>>> tuple(inspect.getargspec(f)) |
(['a', 'b', 'c'], None, None, None) |
(['a', 'b', 'c'], None, None, None) |
|
|
Although Python code objects want ``co_varnames`` to be a tuple, ``Code`` |
Although Python code objects want ``co_varnames`` to be a tuple, ``Code`` |
code that might be unreachable. For example, consider this ``If`` |
code that might be unreachable. For example, consider this ``If`` |
implementation:: |
implementation:: |
|
|
>>> from peak.util.assembler import Pass |
|
>>> def If(cond, then, else_=Pass, code=None): |
>>> def If(cond, then, else_=Pass, code=None): |
... if code is None: |
... if code is None: |
... return cond, then, else_ |
... return cond, then, else_ |
It works okay if there's no dead code:: |
It works okay if there's no dead code:: |
|
|
>>> c = Code() |
>>> c = Code() |
>>> c( If(23, 42, 55) ) |
>>> c( If(Local('a'), 42, 55) ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (23) |
LOAD_FAST 0 (a) |
3 JUMP_IF_FALSE 7 (to 13) |
JUMP_IF_FALSE L1 |
6 POP_TOP |
POP_TOP |
7 LOAD_CONST 2 (42) |
LOAD_CONST 1 (42) |
10 JUMP_FORWARD 4 (to 17) |
JUMP_FORWARD L2 |
>> 13 POP_TOP |
L1: POP_TOP |
14 LOAD_CONST 3 (55) |
LOAD_CONST 2 (55) |
|
|
But it breaks if you end the "then" block with a return:: |
But it breaks if you end the "then" block with a return:: |
|
|
As you can see, the dead code is now eliminated:: |
As you can see, the dead code is now eliminated:: |
|
|
>>> c = Code() |
>>> c = Code() |
>>> c( If(23, Return(42), 55) ) |
>>> c( If(Local('a'), Return(42), 55) ) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (23) |
LOAD_FAST 0 (a) |
3 JUMP_IF_FALSE 5 (to 11) |
JUMP_IF_FALSE L1 |
6 POP_TOP |
POP_TOP |
7 LOAD_CONST 2 (42) |
LOAD_CONST 1 (42) |
10 RETURN_VALUE |
RETURN_VALUE |
>> 11 POP_TOP |
L1: POP_TOP |
12 LOAD_CONST 3 (55) |
LOAD_CONST 2 (55) |
|
|
|
|
Blocks, Loops, and Exception Handling |
Blocks, Loops, and Exception Handling |
>>> c.POP_TOP() |
>>> c.POP_TOP() |
>>> else_() |
>>> else_() |
>>> c.return_() |
>>> c.return_() |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_EXCEPT 4 (to 7) |
SETUP_EXCEPT L1 |
3 POP_BLOCK |
POP_BLOCK |
4 JUMP_FORWARD 3 (to 10) |
JUMP_FORWARD L2 |
>> 7 POP_TOP |
L1: POP_TOP |
8 POP_TOP |
POP_TOP |
9 POP_TOP |
POP_TOP |
>> 10 LOAD_CONST 0 (None) |
L2: LOAD_CONST 0 (None) |
13 RETURN_VALUE |
RETURN_VALUE |
|
|
In the example above, an empty block executes with an exception handler that |
In the example above, an empty block executes with an exception handler that |
begins at offset 7. When the block is done, it jumps forward to the end of |
begins at offset 7. When the block is done, it jumps forward to the end of |
... Return() |
... Return() |
... ) |
... ) |
|
|
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_EXCEPT 4 (to 7) |
SETUP_EXCEPT L1 |
3 POP_BLOCK |
POP_BLOCK |
4 JUMP_FORWARD 3 (to 10) |
JUMP_FORWARD L2 |
>> 7 POP_TOP |
L1: POP_TOP |
8 POP_TOP |
POP_TOP |
9 POP_TOP |
POP_TOP |
>> 10 LOAD_CONST 0 (None) |
L2: LOAD_CONST 0 (None) |
13 RETURN_VALUE |
RETURN_VALUE |
|
|
|
(Labels have a ``POP_BLOCK`` attribute that you can pass in when generating |
|
code.) |
|
|
|
And, for generating typical try/except blocks, you can use the ``TryExcept`` |
|
node type, which takes a body, a sequence of exception-type/handler pairs, |
|
and an optional "else" clause:: |
|
|
|
>>> from peak.util.assembler import TryExcept |
|
>>> c = Code() |
|
>>> c.return_( |
|
... TryExcept( |
|
... Return(1), # body |
|
... [(Const(KeyError),2), (Const(TypeError),3)], # handlers |
|
... Return(4) # else clause |
|
... ) |
|
... ) |
|
|
Labels have a ``POP_BLOCK`` attribute that you can pass in when generating |
>>> dump(c.code()) |
code. |
SETUP_EXCEPT L1 |
|
LOAD_CONST 1 (1) |
|
RETURN_VALUE |
|
POP_BLOCK |
|
JUMP_FORWARD L4 |
|
L1: DUP_TOP |
|
LOAD_CONST 2 (<...exceptions.KeyError...>) |
|
COMPARE_OP 10 (exception match) |
|
JUMP_IF_FALSE L2 |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
LOAD_CONST 3 (2) |
|
JUMP_FORWARD L5 |
|
L2: POP_TOP |
|
DUP_TOP |
|
LOAD_CONST 4 (<...exceptions.TypeError...>) |
|
COMPARE_OP 10 (exception match) |
|
JUMP_IF_FALSE L3 |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
LOAD_CONST 5 (3) |
|
JUMP_FORWARD L5 |
|
L3: POP_TOP |
|
END_FINALLY |
|
L4: LOAD_CONST 6 (4) |
|
RETURN_VALUE |
|
L5: RETURN_VALUE |
|
|
|
|
Try/Finally Blocks |
Try/Finally Blocks |
|
|
And it produces code that looks like this:: |
And it produces code that looks like this:: |
|
|
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_FINALLY 4 (to 7) |
SETUP_FINALLY L1 |
3 POP_BLOCK |
POP_BLOCK |
4 LOAD_CONST 0 (None) |
LOAD_CONST 0 (None) |
>> 7 END_FINALLY |
L1: END_FINALLY |
|
|
The ``END_FINALLY`` opcode will remove 1, 2, or 3 values from the stack at |
The ``END_FINALLY`` opcode will remove 1, 2, or 3 values from the stack at |
runtime, depending on how the "try" block was exited. In the case of simply |
runtime, depending on how the "try" block was exited. In the case of simply |
adjusts the maximum expected stack size to accomodate up to three values being |
adjusts the maximum expected stack size to accomodate up to three values being |
put on the stack by the Python interpreter for exception handling. |
put on the stack by the Python interpreter for exception handling. |
|
|
|
For your convenience, the ``TryFinally`` node type can also be used to generate |
|
try/finally blocks:: |
|
|
|
>>> from peak.util.assembler import TryFinally |
|
>>> c = Code() |
|
>>> c( TryFinally(ExprStmt(1), ExprStmt(2)) ) |
|
>>> dump(c.code()) |
|
SETUP_FINALLY L1 |
|
LOAD_CONST 1 (1) |
|
POP_TOP |
|
POP_BLOCK |
|
LOAD_CONST 0 (None) |
|
L1: LOAD_CONST 2 (2) |
|
POP_TOP |
|
END_FINALLY |
|
|
|
|
Loops |
Loops |
----- |
----- |
... Return() |
... Return() |
... ) |
... ) |
|
|
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_LOOP 19 (to 22) |
SETUP_LOOP L3 |
3 LOAD_CONST 1 (5) |
LOAD_CONST 1 (5) |
>> 6 JUMP_IF_FALSE 7 (to 16) |
L1: JUMP_IF_FALSE L2 |
9 LOAD_CONST 2 (1) |
LOAD_CONST 2 (1) |
12 BINARY_SUBTRACT |
BINARY_SUBTRACT |
13 JUMP_ABSOLUTE 6 |
JUMP_ABSOLUTE L1 |
>> 16 POP_TOP |
L2: POP_TOP |
17 POP_BLOCK |
POP_BLOCK |
18 LOAD_CONST 3 (42) |
LOAD_CONST 3 (42) |
21 RETURN_VALUE |
RETURN_VALUE |
>> 22 LOAD_CONST 0 (None) |
L3: LOAD_CONST 0 (None) |
25 RETURN_VALUE |
RETURN_VALUE |
|
|
>>> eval(c.code()) |
>>> eval(c.code()) |
42 |
42 |
>>> fwd() |
>>> fwd() |
>>> c.BREAK_LOOP() |
>>> c.BREAK_LOOP() |
>>> c.POP_BLOCK()() |
>>> c.POP_BLOCK()() |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (57) |
LOAD_CONST 1 (57) |
3 SETUP_LOOP 8 (to 14) |
SETUP_LOOP L3 |
6 JUMP_IF_TRUE 3 (to 12) |
JUMP_IF_TRUE L2 |
>> 9 JUMP_ABSOLUTE 9 |
L1: JUMP_ABSOLUTE L1 |
>> 12 BREAK_LOOP |
L2: BREAK_LOOP |
13 POP_BLOCK |
POP_BLOCK |
|
|
In other words, ``CONTINUE_LOOP`` only really emits a ``CONTINUE_LOOP`` opcode |
In other words, ``CONTINUE_LOOP`` only really emits a ``CONTINUE_LOOP`` opcode |
if it's inside some other kind of block within the loop, e.g. a "try" clause:: |
if it's inside some other kind of block within the loop, e.g. a "try" clause:: |
>>> c.POP_BLOCK() |
>>> c.POP_BLOCK() |
>>> c.END_FINALLY() |
>>> c.END_FINALLY() |
>>> c.POP_BLOCK()() |
>>> c.POP_BLOCK()() |
|
>>> dump(c.code()) |
|
LOAD_CONST 1 (57) |
|
SETUP_LOOP L4 |
|
L1: SETUP_FINALLY L3 |
|
JUMP_IF_TRUE L2 |
|
CONTINUE_LOOP L1 |
|
L2: POP_BLOCK |
|
LOAD_CONST 0 (None) |
|
L3: END_FINALLY |
|
POP_BLOCK |
|
|
|
``for`` Loops |
|
------------- |
|
|
|
There is a ``For()`` node type available for generating simple loops (without |
|
break/continue support). It takes an iterable expression, an assignment |
|
clause, and a loop body:: |
|
|
|
>>> from peak.util.assembler import For |
|
>>> y = Call(Const(range), (3,)) |
|
>>> x = LocalAssign('x') |
|
>>> body = Suite([Local('x'), Code.PRINT_EXPR]) |
|
|
|
>>> c = Code() |
|
>>> c(For(y, x, body)) # for x in range(3): print x |
|
>>> c.return_() |
|
>>> dump(c.code()) |
|
LOAD_CONST 1 ([0, 1, 2]) |
|
GET_ITER |
|
L1: FOR_ITER L2 |
|
STORE_FAST 0 (x) |
|
LOAD_FAST 0 (x) |
|
PRINT_EXPR |
|
JUMP_ABSOLUTE L1 |
|
L2: LOAD_CONST 0 (None) |
|
RETURN_VALUE |
|
|
|
The arguments are given in execution order: first the "in" value of the loop, |
|
then the assignment to a loop variable, and finally the body of the loop. The |
|
distinction between the assignment and body, however, is only for clarity and |
|
convenience (to avoid needing to glue the assignment to the body with a |
|
``Suite``). If you already have a suite or only need one node for the entire |
|
loop body, you can do the same thing with only two arguments:: |
|
|
|
>>> c = Code() |
|
>>> c(For(y, Code.PRINT_EXPR)) |
|
>>> c.return_() |
|
>>> dump(c.code()) |
|
LOAD_CONST 1 ([0, 1, 2]) |
|
GET_ITER |
|
L1: FOR_ITER L2 |
|
PRINT_EXPR |
|
JUMP_ABSOLUTE L1 |
|
L2: LOAD_CONST 0 (None) |
|
RETURN_VALUE |
|
|
|
Notice, by the way, that ``For()`` does NOT set up a loop block for you, so if |
|
you want to be able to use break and continue, you'll need to wrap the loop in |
|
a labelled SETUP_LOOP/POP_BLOCK pair, as described in the preceding sections. |
|
|
|
|
|
List Comprehensions |
|
------------------- |
|
|
|
In order to generate correct list comprehension code for the target Python |
|
version, you must use the ``ListComp()`` and ``LCAppend()`` node types. This |
|
is because Python versions 2.4 and up store the list being built in a temporary |
|
variable, and use a special ``LIST_APPEND`` opcode to append values, while 2.3 |
|
stores the list's ``append()`` method in the temporary variable, and calls it |
|
to append values. |
|
|
|
The ``ListComp()`` node wraps a code body (usually a ``For()`` loop) and |
|
manages the creation and destruction of a temporary variable (e.g. ``_[1]``, |
|
``_[2]``, etc.). The ``LCAppend()`` node type wraps a value or expression to |
|
be appended to the innermost active ``ListComp()`` in progress:: |
|
|
|
>>> from peak.util.assembler import ListComp, LCAppend |
|
>>> c = Code() |
|
>>> simple = ListComp(For(y, x, LCAppend(Local('x')))) |
|
>>> c.return_(simple) |
|
>>> eval(c.code()) |
|
[0, 1, 2] |
|
|
|
>>> c = Code() |
|
>>> c.return_(ListComp(For(y, x, LCAppend(simple)))) |
|
>>> eval(c.code()) |
|
[[0, 1, 2], [0, 1, 2], [0, 1, 2]] |
|
|
|
|
|
Closures and Nested Functions |
|
============================= |
|
|
|
Free and Cell Variables |
|
----------------------- |
|
|
|
To implement closures and nested scopes, your code objects must use "free" or |
|
"cell" variables in place of regular "fast locals". A "free" variable is one |
|
that is defined in an outer scope, and a "cell" variable is one that's defined |
|
in the current scope, but will also be used by nested functions. |
|
|
|
The simplest way to set up free or cell variables is to use a code object's |
|
``makefree(names)`` and ``makecells(names)`` methods:: |
|
|
|
>>> c = Code() |
|
>>> c.co_cellvars |
|
() |
|
>>> c.co_freevars |
|
() |
|
|
|
>>> c.makefree(['x', 'y']) |
|
>>> c.makecells(['z']) |
|
|
|
>>> c.co_cellvars |
|
('z',) |
|
>>> c.co_freevars |
|
('x', 'y') |
|
|
|
When a name has been defined as a free or cell variable, the ``_DEREF`` opcode |
|
variants are used to generate ``Local()`` and ``LocalAssign()`` nodes:: |
|
|
|
>>> c((Local('x'), Local('y')), LocalAssign('z')) |
|
>>> dis(c.code()) |
|
0 0 LOAD_DEREF 1 (x) |
|
3 LOAD_DEREF 2 (y) |
|
6 BUILD_TUPLE 2 |
|
9 STORE_DEREF 0 (z) |
|
|
|
If you have already written code in a code object that operates on the relevant |
|
locals, the code is retroactively patched to use the ``_DEREF`` opcodes:: |
|
|
|
>>> c = Code() |
|
>>> c((Local('x'), Local('y')), LocalAssign('z')) |
|
>>> dis(c.code()) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_FAST 1 (y) |
|
6 BUILD_TUPLE 2 |
|
9 STORE_FAST 2 (z) |
|
|
|
>>> c.makefree(['x', 'y']) |
|
>>> c.makecells(['z']) |
|
|
|
>>> dis(c.code()) |
|
0 0 LOAD_DEREF 1 (x) |
|
3 LOAD_DEREF 2 (y) |
|
6 BUILD_TUPLE 2 |
|
9 STORE_DEREF 0 (z) |
|
|
|
This means that you can defer the decision of which locals are free/cell |
|
variables until the code is ready to be generated. In fact, by passing in |
|
a "parent" code object to the ``.code()`` method, you can get BytecodeAssembler |
|
to automatically call ``makefree()`` and ``makecells()`` for the correct |
|
variable names in the child and parent code objects, as we'll see in the next |
|
section. |
|
|
|
|
|
Nested Code Objects |
|
------------------- |
|
|
|
To create a code object for use in a nested scope, you can use the parent code |
|
object's ``nested()`` method. It works just like the ``from_spec()`` |
|
classmethod, except that the ``co_filename`` of the parent is copied to the |
|
child:: |
|
|
|
>>> p = Code() |
|
>>> p.co_filename = 'testname' |
|
|
|
>>> c = p.nested('sub', ['a','b'], 'c', 'd') |
|
|
|
>>> c.co_name |
|
'sub' |
|
|
|
>>> c.co_filename |
|
'testname' |
|
|
|
>>> tuple(inspect.getargs(c.code(p))) |
|
(['a', 'b'], 'c', 'd') |
|
|
|
Notice that you must pass the parent code object to the child's ``.code()`` |
|
method to ensure that free/cell variables are properly set up. When the |
|
``code()`` method is given another code object as a parameter, it automatically |
|
converts any locally-read (but not written) to "free" variables in the child |
|
code, and ensures that those same variables become "cell" variables in the |
|
supplied parent code object:: |
|
|
|
>>> p.LOAD_CONST(42) |
|
>>> p(LocalAssign('a')) |
|
>>> dis(p.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 0 (a) |
|
|
|
>>> c = p.nested() |
|
>>> c(Local('a')) |
|
|
|
>>> dis(c.code(p)) |
|
0 0 LOAD_DEREF 0 (a) |
|
|
|
>>> dis(p.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 0 (a) |
|
|
|
Notice that the ``STORE_FAST`` in the parent code object was automatically |
|
patched to a ``STORE_DEREF``, with an updated offset if applicable. Any |
|
future use of ``Local('a')`` or ``LocalAssign('a')`` in the parent or child |
|
code objects will now refer to the free/cell variable, rather than the "local" |
|
variable:: |
|
|
|
>>> p(Local('a')) |
|
>>> dis(p.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 0 (a) |
|
6 LOAD_DEREF 0 (a) |
|
|
|
>>> c(LocalAssign('a')) |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_DEREF 0 (a) |
|
3 STORE_DEREF 0 (a) |
|
|
|
|
|
``Function()`` |
|
-------------- |
|
|
|
The ``Function(body, name='<lambda>', args=(), var=None, kw=None, defaults=())`` |
|
node type creates a function object from the specified body and the optional |
|
name, argument specs, and defaults. The ``Function()`` node generates code to |
|
create the function object with the appropriate defaults and closure (if |
|
applicable), and any needed free/cell variables are automatically set up in the |
|
parent and child code objects. The newly generated function will be on top of |
|
the stack at the end of the generated code:: |
|
|
|
>>> from peak.util.assembler import Function |
|
>>> c = Code() |
|
>>> c.co_filename = '<string>' |
|
>>> c.return_(Function(Return(Local('a')), 'f', ['a'], defaults=[42])) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 LOAD_CONST 2 (<... f ..., file "<string>", line -1>) |
|
6 MAKE_FUNCTION 1 |
|
9 RETURN_VALUE |
|
|
|
Now that we've generated the code for a function returning a function, let's |
|
run it, to get the function we defined:: |
|
|
|
>>> f = eval(c.code()) |
|
>>> f |
|
<function f at ...> |
|
|
|
>>> tuple(inspect.getargspec(f)) |
|
(['a'], None, None, (42,)) |
|
|
|
>>> f() |
|
42 |
|
|
|
>>> f(99) |
|
99 |
|
|
|
Now let's create a doubly nested function, with some extras:: |
|
|
|
>>> c = Code() |
|
>>> c.co_filename = '<string>' |
|
>>> c.return_( |
|
... Function(Return(Function(Return(Local('a')))), |
|
... 'f', ['a', 'b'], 'c', 'd', [99, 66]) |
|
... ) |
>>> dis(c.code()) |
>>> dis(c.code()) |
0 0 LOAD_CONST 1 (57) |
0 0 LOAD_CONST 1 (99) |
3 SETUP_LOOP 15 (to 21) |
3 LOAD_CONST 2 (66) |
>> 6 SETUP_FINALLY 10 (to 19) |
6 LOAD_CONST 3 (<... f ..., file "<string>", line -1>) |
9 JUMP_IF_TRUE 3 (to 15) |
9 MAKE_FUNCTION 2 |
12 CONTINUE_LOOP 6 |
12 RETURN_VALUE |
>> 15 POP_BLOCK |
|
16 LOAD_CONST 0 (None) |
>>> f = eval(c.code()) |
>> 19 END_FINALLY |
>>> f |
20 POP_BLOCK |
<function f at ...> |
|
|
|
>>> tuple(inspect.getargspec(f)) |
|
(['a', 'b'], 'c', 'd', (99, 66)) |
|
|
|
>>> dis(f) |
|
0 0 LOAD_CLOSURE 0 (a) |
|
... LOAD_CONST 1 (<... <lambda> ..., file "<string>", line -1>) |
|
... MAKE_CLOSURE 0 |
|
... RETURN_VALUE |
|
|
|
>>> dis(f()) |
|
0 0 LOAD_DEREF 0 (a) |
|
3 RETURN_VALUE |
|
|
|
>>> f(42)() |
|
42 |
|
|
|
>>> f()() |
|
99 |
|
|
|
As you can see, ``Function()`` not only takes care of setting up free/cell |
|
variables in all the relevant scopes, it also chooses whether to use |
|
``MAKE_FUNCTION`` or ``MAKE_CLOSURE``, and generates code for the defaults. |
|
|
|
(Note, by the way, that the `defaults` argument should be a sequence of |
|
generatable expressions; in the examples here, we used numbers, but they could |
|
have been arbitrary expression nodes.) |
|
|
|
|
---------------------- |
---------------------- |
>>> simple_code(1,1).co_stacksize |
>>> simple_code(1,1).co_stacksize |
1 |
1 |
|
|
>>> dis(simple_code(13,414)) # FAILURE EXPECTED IN PYTHON 2.3 |
>>> dis(simple_code(13,414)) |
13 0 LOAD_CONST 0 (None) |
13 0 LOAD_CONST 0 (None) |
414 3 RETURN_VALUE |
414 3 RETURN_VALUE |
|
|
>>> simple_code(13,14,100).co_stacksize |
>>> simple_code(13,14,100).co_stacksize |
100 |
100 |
|
|
>>> dis(simple_code(13,572,120)) # FAILURE EXPECTED IN Python 2.3 |
>>> dis(simple_code(13,572,120)) |
13 0 LOAD_CONST 0 (None) |
13 0 LOAD_CONST 0 (None) |
3 LOAD_CONST 0 (None) |
3 LOAD_CONST 0 (None) |
... |
... |
3 LOAD_ATTR 1 (bar) |
3 LOAD_ATTR 1 (bar) |
6 DELETE_FAST 0 (baz) |
6 DELETE_FAST 0 (baz) |
|
|
|
Code iteration:: |
|
|
|
>>> c.DUP_TOP() |
|
>>> c.return_(Code.POP_TOP) |
|
>>> list(c) == [ |
|
... (0, op.LOAD_GLOBAL, 0), |
|
... (3, op.LOAD_ATTR, 1), |
|
... (6, op.DELETE_FAST, 0), |
|
... (9, op.DUP_TOP, None), |
|
... (10, op.POP_TOP, None), |
|
... (11, op.RETURN_VALUE, None) |
|
... ] |
|
True |
|
|
|
Code patching:: |
|
|
|
>>> c = Code() |
|
>>> c.LOAD_CONST(42) |
|
>>> c.STORE_FAST('x') |
|
>>> c.LOAD_FAST('x') |
|
>>> c.DELETE_FAST('x') |
|
>>> c.RETURN_VALUE() |
|
|
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 0 (x) |
|
6 LOAD_FAST 0 (x) |
|
9 DELETE_FAST 0 (x) |
|
12 RETURN_VALUE |
|
|
|
|
|
>>> c.co_varnames |
|
['x'] |
|
>>> c.co_varnames.append('y') |
|
|
|
>>> c._patch( |
|
... {op.LOAD_FAST: op.LOAD_FAST, |
|
... op.STORE_FAST: op.STORE_FAST, |
|
... op.DELETE_FAST: op.DELETE_FAST}, |
|
... {0: 1} |
|
... ) |
|
|
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 1 (y) |
|
6 LOAD_FAST 1 (y) |
|
9 DELETE_FAST 1 (y) |
|
12 RETURN_VALUE |
|
|
|
>>> c._patch({op.RETURN_VALUE: op.POP_TOP}) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 1 (y) |
|
6 LOAD_FAST 1 (y) |
|
9 DELETE_FAST 1 (y) |
|
12 POP_TOP |
|
|
|
Converting locals to free/cell vars:: |
|
|
|
>>> c = Code() |
|
>>> c.LOAD_CONST(42) |
|
>>> c.STORE_FAST('x') |
|
>>> c.LOAD_FAST('x') |
|
|
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_FAST 0 (x) |
|
6 LOAD_FAST 0 (x) |
|
|
|
>>> c.co_freevars = 'y', 'x' |
|
>>> c.co_cellvars = 'z', |
|
|
|
>>> c._locals_to_cells() |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 2 (x) |
|
6 LOAD_DEREF 2 (x) |
|
|
|
>>> c.DELETE_FAST('x') |
|
>>> c._locals_to_cells() |
|
Traceback (most recent call last): |
|
... |
|
AssertionError: Can't delete local 'x' used in nested scope |
|
|
|
>>> c = Code() |
|
>>> c.LOAD_CONST(42) |
|
>>> c.STORE_FAST('x') |
|
>>> c.LOAD_FAST('x') |
|
|
|
>>> c.co_freevars |
|
() |
|
>>> c.makefree(['x']) |
|
>>> c.co_freevars |
|
('x',) |
|
|
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 0 (x) |
|
6 LOAD_DEREF 0 (x) |
|
|
|
>>> c = Code() |
|
>>> c.LOAD_CONST(42) |
|
>>> c.STORE_FAST('x') |
|
>>> c.LOAD_FAST('x') |
|
>>> c.makecells(['x']) |
|
>>> c.co_freevars |
|
() |
|
>>> c.co_cellvars |
|
('x',) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 0 (x) |
|
6 LOAD_DEREF 0 (x) |
|
|
|
>>> c = Code() |
|
>>> c.LOAD_CONST(42) |
|
>>> c.STORE_FAST('x') |
|
>>> c.LOAD_FAST('x') |
|
>>> c.makefree('x') |
|
>>> c.makecells(['y']) |
|
>>> c.co_freevars |
|
('x',) |
|
>>> c.co_cellvars |
|
('y',) |
|
>>> dis(c.code()) |
|
0 0 LOAD_CONST 1 (42) |
|
3 STORE_DEREF 1 (x) |
|
6 LOAD_DEREF 1 (x) |
|
|
|
>>> c = Code() |
|
>>> c.co_flags &= ~op.CO_OPTIMIZED |
|
>>> c.makecells(['q']) |
|
Traceback (most recent call last): |
|
... |
|
AssertionError: Can't use cellvars in unoptimized scope |
|
|
|
|
|
|
|
Auto-free promotion with code parent: |
|
|
|
>>> p = Code() |
|
>>> c = Code() |
|
>>> c.LOAD_FAST('x') |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_DEREF 0 (x) |
|
>>> p.co_cellvars |
|
('x',) |
|
|
|
>>> p = Code() |
|
>>> c = Code.from_function(lambda x,y,z=2: None) |
|
>>> c.LOAD_FAST('x') |
|
>>> c.LOAD_FAST('y') |
|
>>> c.LOAD_FAST('z') |
|
|
|
>>> dis(c.code(p)) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_FAST 1 (y) |
|
6 LOAD_FAST 2 (z) |
|
>>> p.co_cellvars |
|
() |
|
|
|
>>> c.LOAD_FAST('q') |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_FAST 1 (y) |
|
6 LOAD_FAST 2 (z) |
|
9 LOAD_DEREF 0 (q) |
|
>>> p.co_cellvars |
|
('q',) |
|
|
|
>>> p = Code() |
|
>>> c = Code.from_function(lambda x,*y,**z: None) |
|
>>> c.LOAD_FAST('q') |
|
>>> c.LOAD_FAST('x') |
|
>>> c.LOAD_FAST('y') |
|
>>> c.LOAD_FAST('z') |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_DEREF 0 (q) |
|
3 LOAD_FAST 0 (x) |
|
6 LOAD_FAST 1 (y) |
|
9 LOAD_FAST 2 (z) |
|
>>> p.co_cellvars |
|
('q',) |
|
|
|
>>> p = Code() |
|
>>> c = Code.from_function(lambda x,*y: None) |
|
>>> c.LOAD_FAST('x') |
|
>>> c.LOAD_FAST('y') |
|
>>> c.LOAD_FAST('z') |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_FAST 1 (y) |
|
6 LOAD_DEREF 0 (z) |
|
>>> p.co_cellvars |
|
('z',) |
|
|
|
>>> p = Code() |
|
>>> c = Code.from_function(lambda x,**y: None) |
|
>>> c.LOAD_FAST('x') |
|
>>> c.LOAD_FAST('y') |
|
>>> c.LOAD_FAST('z') |
|
>>> dis(c.code(p)) |
|
0 0 LOAD_FAST 0 (x) |
|
3 LOAD_FAST 1 (y) |
|
6 LOAD_DEREF 0 (z) |
|
>>> p.co_cellvars |
|
('z',) |
|
|
|
|
Stack tracking on jumps:: |
Stack tracking on jumps:: |
|
|
>>> end = Label() |
>>> end = Label() |
>>> c(99, else_.JUMP_IF_TRUE, Code.POP_TOP, end.JUMP_FORWARD) |
>>> c(99, else_.JUMP_IF_TRUE, Code.POP_TOP, end.JUMP_FORWARD) |
>>> c(else_, Code.POP_TOP, end) |
>>> c(else_, Code.POP_TOP, end) |
>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 LOAD_CONST 1 (99) |
LOAD_CONST 1 (99) |
3 JUMP_IF_TRUE 4 (to 10) |
JUMP_IF_TRUE L1 |
6 POP_TOP |
POP_TOP |
7 JUMP_FORWARD 1 (to 11) |
JUMP_FORWARD L2 |
>> 10 POP_TOP |
L1: POP_TOP |
|
|
>>> c.stack_size |
>>> c.stack_size |
0 |
0 |
>>> c.stack_history |
>>> if sys.version>='2.7': |
[0, 1, 1, 1, 1, 1, 1, 0, None, None, 1] |
... print c.stack_history == [0, 1, 1, 1, 2, 1, 1, 1, 0, None, None, 1] |
|
... else: |
|
... print c.stack_history == [0, 1, 1, 1, 1, 1, 1, 0, None, None, 1] |
|
True |
|
|
|
|
>>> c = Code() |
>>> c = Code() |
>>> fwd = c.JUMP_FORWARD() |
>>> fwd = c.JUMP_FORWARD() |
... |
... |
AssertionError: Stack level mismatch: actual=1 expected=0 |
AssertionError: Stack level mismatch: actual=1 expected=0 |
|
|
|
>>> from peak.util.assembler import For |
|
>>> c = Code() |
|
>>> c(For((), Code.POP_TOP, Pass)) |
|
>>> c.return_() |
|
>>> dump(c.code()) |
|
BUILD_TUPLE 0 |
|
GET_ITER |
|
L1: FOR_ITER L2 |
|
POP_TOP |
|
JUMP_ABSOLUTE L1 |
|
L2: LOAD_CONST 0 (None) |
|
RETURN_VALUE |
|
|
|
>>> c.stack_history |
|
[0, 1, 1, 1, 1, 2, 2, 2, 1, None, None, 0, 1, 1, 1] |
|
|
|
|
|
Yield value:: |
|
|
|
>>> import sys |
|
>>> from peak.util.assembler import CO_GENERATOR |
|
>>> c = Code() |
|
>>> c.co_flags & CO_GENERATOR |
|
0 |
|
>>> c(42, Code.YIELD_VALUE) |
|
>>> c.stack_size == int(sys.version>='2.5') |
|
True |
|
>>> (c.co_flags & CO_GENERATOR) == CO_GENERATOR |
|
True |
|
|
|
|
|
|
... |
... |
AssertionError: Stack underflow |
AssertionError: Stack underflow |
|
|
>>> c.LOAD_CONST(1) |
>>> c = Code() |
>>> c.LOAD_CONST(2) # simulate being a function |
>>> c.LOAD_CONST(1) # closure |
>>> c.MAKE_CLOSURE(1, 0) |
>>> if sys.version>='2.5': c.BUILD_TUPLE(1) |
|
>>> c.LOAD_CONST(2) # default |
|
>>> c.LOAD_CONST(3) # simulate being a function |
|
>>> c.MAKE_CLOSURE(1, 1) |
>>> c.stack_size |
>>> c.stack_size |
1 |
1 |
|
|
>>> c = Code() |
>>> c = Code() |
>>> c.LOAD_CONST(1) |
>>> c.LOAD_CONST(1) |
>>> c.LOAD_CONST(2) |
>>> c.LOAD_CONST(2) |
|
>>> if sys.version>='2.5': c.BUILD_TUPLE(2) |
>>> c.LOAD_CONST(3) # simulate being a function |
>>> c.LOAD_CONST(3) # simulate being a function |
>>> c.MAKE_CLOSURE(1, 1) |
>>> c.MAKE_CLOSURE(0, 2) |
>>> c.stack_size |
>>> c.stack_size |
1 |
1 |
|
|
|
|
|
|
Labels and backpatching forward references:: |
Labels and backpatching forward references:: |
|
|
>>> c = Code() |
>>> c = Code() |
>>> where = c.here() |
>>> where = c.here() |
>>> c.LOAD_CONST(1) |
>>> c.LOAD_CONST(1) |
>>> c.JUMP_IF_TRUE(where) |
>>> c.JUMP_FORWARD(where) |
Traceback (most recent call last): |
Traceback (most recent call last): |
... |
... |
AssertionError: Relative jumps can't go backwards |
AssertionError: Relative jumps can't go backwards |
0 0 LOAD_CONST 1 ({'x': 1}) |
0 0 LOAD_CONST 1 ({'x': 1}) |
3 RETURN_VALUE |
3 RETURN_VALUE |
|
|
|
Try/Except stack level tracking:: |
|
|
|
>>> def class_or_type_of(expr): |
|
... return Suite([expr, TryExcept( |
|
... Suite([Getattr(Code.DUP_TOP, '__class__'), Code.ROT_TWO]), |
|
... [(Const(AttributeError), Call(Const(type), (Code.ROT_TWO,)))] |
|
... )]) |
|
|
|
>>> def type_or_class(x): pass |
|
>>> c = Code.from_function(type_or_class) |
|
>>> c.return_(class_or_type_of(Local('x'))) |
|
>>> dump(c.code()) |
|
LOAD_FAST 0 (x) |
|
SETUP_EXCEPT L1 |
|
DUP_TOP |
|
LOAD_ATTR 0 (__class__) |
|
ROT_TWO |
|
POP_BLOCK |
|
JUMP_FORWARD L3 |
|
L1: DUP_TOP |
|
LOAD_CONST 1 (<...exceptions.AttributeError...>) |
|
COMPARE_OP 10 (exception match) |
|
JUMP_IF_FALSE L2 |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
POP_TOP |
|
LOAD_CONST 2 (<type 'type'>) |
|
ROT_TWO |
|
CALL_FUNCTION 1 |
|
JUMP_FORWARD L3 |
|
L2: POP_TOP |
|
END_FINALLY |
|
L3: RETURN_VALUE |
|
|
|
>>> type_or_class.func_code = c.code() |
|
>>> type_or_class(23) |
|
<type 'int'> |
|
|
|
|
|
|
|
|
|
|
Demo: "Computed Goto"/"Switch Statement" |
Demo: "Computed Goto"/"Switch Statement" |
======================================== |
======================================== |
|
|
>>> from peak.util.assembler import LOAD_CONST, POP_BLOCK |
>>> from peak.util.assembler import LOAD_CONST, POP_BLOCK |
|
|
>>> def Pass(code=None): |
|
... if code is None: |
|
... return Pass |
|
|
|
>>> import sys |
>>> import sys |
>>> WHY_CONTINUE = {'2.3':5, '2.4':32, '2.5':32}[sys.version[:3]] |
>>> WHY_CONTINUE = {'2.3':5}.get(sys.version[:3], 32) |
|
|
>>> def Switch(expr, cases, default=Pass, code=None): |
>>> def Switch(expr, cases, default=Pass, code=None): |
... if code is None: |
... if code is None: |
>>> f(3) |
>>> f(3) |
27 |
27 |
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>>> dis(c.code()) |
>>> dump(c.code()) |
0 0 SETUP_LOOP 30 (to 33) |
SETUP_LOOP L2 |
3 LOAD_CONST 1 (<...method get of dict...>) |
LOAD_CONST 1 (<...method get of dict...>) |
6 LOAD_FAST 0 (x) |
LOAD_FAST 0 (x) |
9 CALL_FUNCTION 1 |
CALL_FUNCTION 1 |
12 JUMP_IF_FALSE 12 (to 27) |
JUMP_IF_FALSE L1 |
15 LOAD_CONST 2 (...) |
LOAD_CONST 2 (...) |
18 END_FINALLY |
END_FINALLY |
19 LOAD_CONST 3 (42) |
LOAD_CONST 3 (42) |
22 RETURN_VALUE |
RETURN_VALUE |
23 LOAD_CONST 4 ('foo') |
LOAD_CONST 4 ('foo') |
26 RETURN_VALUE |
RETURN_VALUE |
>> 27 POP_TOP |
L1: POP_TOP |
28 LOAD_CONST 5 (27) |
LOAD_CONST 5 (27) |
31 RETURN_VALUE |
RETURN_VALUE |
32 POP_BLOCK |
POP_BLOCK |
>> 33 LOAD_CONST 0 (None) |
L2: LOAD_CONST 0 (None) |
36 RETURN_VALUE |
RETURN_VALUE |
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TODO |
TODO |
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* Exhaustive tests of all opcodes' stack history effects |
* Exhaustive tests of all opcodes' stack history effects |
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* YIELD_EXPR should set CO_GENERATOR; stack effects depend on Python version |
* Test wide jumps and wide argument generation in general |
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