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[3.9] bpo-42218: Correctly handle errors in left-recursive rules (GH-23065) (GH-23066)

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Left-recursive rules need to check for errors explicitly, since
even if the rule returns NULL, the parsing might continue and lead
to long-distance failures.

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
(cherry picked from commit 02cdfc93f8)

Automerge-Triggered-By: GH:lysnikolaou
This commit is contained in:
Lysandros Nikolaou 2020-10-31 21:06:03 +02:00 • committed by GitHub
parent dbaa07db67
commit cfcb952e30
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4 changed files with 32 additions and 0 deletions
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8
Lib/test/test_syntax.py
View file

@ -964,6 +964,14 @@ def func2():
"""
self._check_error(code, "invalid syntax")
def test_invalid_line_continuation_left_recursive(self):
# Check bpo-42218: SyntaxErrors following left-recursive rules
# (t_primary_raw in this case) need to be tested explicitly
self._check_error("A.\u018a\\ ",
"unexpected character after line continuation character")
self._check_error("A.\u03bc\\\n",
"unexpected EOF while parsing")
def test_main():
support.run_unittest(SyntaxTestCase)
from test import test_syntax

3
Misc/NEWS.d/next/Core and Builtins/2020-10-31-17-50-23.bpo-42218.Dp_Z3v.rst Normal file
View file

@ -0,0 +1,3 @@
Fixed a bug in the PEG parser that was causing crashes in debug mode. Now errors are checked
in left-recursive rules to avoid cases where such errors do not get handled in time and appear
as long-distance crashes in other places.

18
Parser/pegen/parse.c
View file

@ -3460,6 +3460,8 @@ dotted_name_rule(Parser *p)
}
p->mark = _mark;
void *_raw = dotted_name_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9044,6 +9046,8 @@ bitwise_or_rule(Parser *p)
}
p->mark = _mark;
void *_raw = bitwise_or_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9158,6 +9162,8 @@ bitwise_xor_rule(Parser *p)
}
p->mark = _mark;
void *_raw = bitwise_xor_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9272,6 +9278,8 @@ bitwise_and_rule(Parser *p)
}
p->mark = _mark;
void *_raw = bitwise_and_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9386,6 +9394,8 @@ shift_expr_rule(Parser *p)
}
p->mark = _mark;
void *_raw = shift_expr_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9539,6 +9549,8 @@ sum_rule(Parser *p)
}
p->mark = _mark;
void *_raw = sum_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -9698,6 +9710,8 @@ term_rule(Parser *p)
}
p->mark = _mark;
void *_raw = term_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -10302,6 +10316,8 @@ primary_rule(Parser *p)
}
p->mark = _mark;
void *_raw = primary_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;
@ -13962,6 +13978,8 @@ t_primary_rule(Parser *p)
}
p->mark = _mark;
void *_raw = t_primary_raw(p);
if (p->error_indicator)
return NULL;
if (_raw == NULL || p->mark <= _resmark)
break;
_resmark = p->mark;

3
Tools/peg_generator/pegen/c_generator.py
View file

@ -496,6 +496,9 @@ def _set_up_rule_memoization(self, node: Rule, result_type: str) -> None:
)
self.print("p->mark = _mark;")
self.print(f"void *_raw = {node.name}_raw(p);")
self.print("if (p->error_indicator)")
with self.indent():
self.print("return NULL;")
self.print("if (_raw == NULL || p->mark <= _resmark)")
with self.indent():
self.print("break;")