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Pegen improperly memoizes loop rules #102416

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abel1502 opened this issue Mar 4, 2023 · 3 comments
Closed

Pegen improperly memoizes loop rules #102416

abel1502 opened this issue Mar 4, 2023 · 3 comments
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interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@abel1502
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abel1502 commented Mar 4, 2023

Bug report

In the following part of pegen, the memoized result is only used if self._should_memoize(node) is true. Since loop rules are autogenerated, they are not marked with (memo), so this is always false. Despite that, in the end the result is memoized based on the different condition if node.name. Because of that, in the generated parser loop rules' results are always stored in the cache, but never accessed later.

def _handle_loop_rule_body(self, node: Rule, rhs: Rhs) -> None:
memoize = self._should_memoize(node)
is_repeat1 = node.name.startswith("_loop1")
with self.indent():
self.add_level()
self._check_for_errors()
self.print("void *_res = NULL;")
if memoize:
self.print(f"if (_PyPegen_is_memoized(p, {node.name}_type, &_res)) {{")
with self.indent():
self.add_return("_res")
self.print("}")
self.print("int _mark = p->mark;")
self.print("int _start_mark = p->mark;")
self.print("void **_children = PyMem_Malloc(sizeof(void *));")
self.out_of_memory_return(f"!_children")
self.print("Py_ssize_t _children_capacity = 1;")
self.print("Py_ssize_t _n = 0;")
if any(alt.action and "EXTRA" in alt.action for alt in rhs.alts):
self._set_up_token_start_metadata_extraction()
self.visit(
rhs,
is_loop=True,
is_gather=node.is_gather(),
rulename=node.name,
)
if is_repeat1:
self.print("if (_n == 0 || p->error_indicator) {")
with self.indent():
self.print("PyMem_Free(_children);")
self.add_return("NULL")
self.print("}")
self.print("asdl_seq *_seq = (asdl_seq*)_Py_asdl_generic_seq_new(_n, p->arena);")
self.out_of_memory_return(f"!_seq", cleanup_code="PyMem_Free(_children);")
self.print("for (int i = 0; i < _n; i++) asdl_seq_SET_UNTYPED(_seq, i, _children[i]);")
self.print("PyMem_Free(_children);")
if node.name:
self.print(f"_PyPegen_insert_memo(p, _start_mark, {node.name}_type, _seq);")
self.add_return("_seq")

Your environment

Does not matter - discovered through manual code analysis

Linked PRs

@abel1502 abel1502 added the type-bug An unexpected behavior, bug, or error label Mar 4, 2023
@sobolevn sobolevn added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Mar 4, 2023
@sobolevn
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sobolevn commented Mar 4, 2023

cc @pablogsal

@pablogsal
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Thanks for the report @abel1502 and @sobolevn for the ping!

@pablogsal
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Opened #102467

pablogsal added a commit to pablogsal/cpython that referenced this issue Mar 6, 2023
…parser (pythonGH-102467).

(cherry picked from commit f533f21)

Co-authored-by: Pablo Galindo Salgado <[email protected]>
pablogsal added a commit to pablogsal/cpython that referenced this issue Mar 6, 2023
…parser (pythonGH-102467).

(cherry picked from commit f533f21)

Co-authored-by: Pablo Galindo Salgado <[email protected]>
carljm added a commit to carljm/cpython that referenced this issue Mar 6, 2023
* main: (21 commits)
  pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives in sub interpreters module (python#102472)
  pythongh-95672: Fix versionadded indentation of get_pagesize in test.rst (pythongh-102455)
  pythongh-102416: Do not memoize incorrectly loop rules in the parser (python#102467)
  pythonGH-101362: Optimise PurePath(PurePath(...)) (pythonGH-101667)
  pythonGH-101362: Check pathlib.Path flavour compatibility at import time (pythonGH-101664)
  pythonGH-101362: Call join() only when >1 argument supplied to pathlib.PurePath() (python#101665)
  pythongh-102444: Fix minor bugs in `test_typing` highlighted by pyflakes (python#102445)
  pythonGH-102341: Improve the test function for pow (python#102342)
  Fix unused classes in a typing test (pythonGH-102437)
  pythongh-101979: argparse: fix a bug where parentheses in metavar argument of add_argument() were dropped (python#102318)
  pythongh-102356: Add thrashcan macros to filter object dealloc (python#102426)
  Move around example in to_bytes() to avoid confusion (python#101595)
  pythonGH-97546: fix flaky asyncio `test_wait_for_race_condition` test (python#102421)
  pythongh-96821: Add config option `--with-strict-overflow` (python#96823)
  pythongh-101992: update pstlib module documentation (python#102133)
  pythongh-63301: Set exit code when tabnanny CLI exits on error (python#7699)
  pythongh-101863: Fix wrong comments in EUC-KR codec (pythongh-102417)
  pythongh-102302 Micro-optimize `inspect.Parameter.__hash__` (python#102303)
  pythongh-102179: Fix `os.dup2` error reporting for negative fds (python#102180)
  pythongh-101892: Fix `SystemError` when a callable iterator call exhausts the iterator (python#101896)
  ...
carljm added a commit to carljm/cpython that referenced this issue Mar 7, 2023
* main: (37 commits)
  pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives in sub interpreters module (python#102472)
  pythongh-95672: Fix versionadded indentation of get_pagesize in test.rst (pythongh-102455)
  pythongh-102416: Do not memoize incorrectly loop rules in the parser (python#102467)
  pythonGH-101362: Optimise PurePath(PurePath(...)) (pythonGH-101667)
  pythonGH-101362: Check pathlib.Path flavour compatibility at import time (pythonGH-101664)
  pythonGH-101362: Call join() only when >1 argument supplied to pathlib.PurePath() (python#101665)
  pythongh-102444: Fix minor bugs in `test_typing` highlighted by pyflakes (python#102445)
  pythonGH-102341: Improve the test function for pow (python#102342)
  Fix unused classes in a typing test (pythonGH-102437)
  pythongh-101979: argparse: fix a bug where parentheses in metavar argument of add_argument() were dropped (python#102318)
  pythongh-102356: Add thrashcan macros to filter object dealloc (python#102426)
  Move around example in to_bytes() to avoid confusion (python#101595)
  pythonGH-97546: fix flaky asyncio `test_wait_for_race_condition` test (python#102421)
  pythongh-96821: Add config option `--with-strict-overflow` (python#96823)
  pythongh-101992: update pstlib module documentation (python#102133)
  pythongh-63301: Set exit code when tabnanny CLI exits on error (python#7699)
  pythongh-101863: Fix wrong comments in EUC-KR codec (pythongh-102417)
  pythongh-102302 Micro-optimize `inspect.Parameter.__hash__` (python#102303)
  pythongh-102179: Fix `os.dup2` error reporting for negative fds (python#102180)
  pythongh-101892: Fix `SystemError` when a callable iterator call exhausts the iterator (python#101896)
  ...
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