FazBrowse GitHub Viewer | Trending |
URL:
| Home
Tools: [Download Repo ZIP]   [Original HTTPS Page]

gh-93671: Avoid exponential backtracking in deeply nested sequence patterns in match statements by pablogsal · Pull Request #93680 · python/cpython · GitHub

/ cpython Public

gh-93671: Avoid exponential backtracking in deeply nested sequence patterns in match statements #93680

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ambv merged 2 commits into from
Jun 10, 2022
Conversation 9 Commits 2 Checks 0 Files changed
Merged

gh-93671: Avoid exponential backtracking in deeply nested sequence patterns in match statements #93680

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e042cbb
gh-93671: Avoid exponential backtracking in deeply nested sequence pa…
pablogsal Jun 10, 2022
9907737
s/patters/patterns/
ambv Jun 10, 2022
File filter

Filter by extension

Filter by extension .c  (1) .gram  (1) .py  (1) .rst  (1) All 4 file types selected
Viewed files
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Unified
Split
Hide whitespace
Diff view
Unified
Split
Hide whitespace
6 changes: 3 additions & 3 deletions Grammar/python.gram
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
Expand Up @@ -471,7 +471,7 @@ or_pattern[pattern_ty]:
| patterns[asdl_pattern_seq*]='|'.closed_pattern+ {
asdl_seq_LEN(patterns) == 1 ? asdl_seq_GET(patterns, 0) : _PyAST_MatchOr(patterns, EXTRA) }

closed_pattern[pattern_ty]:
closed_pattern[pattern_ty] (memo):
| literal_pattern
| capture_pattern
| wildcard_pattern
Expand Down Expand Up @@ -558,7 +558,7 @@ maybe_star_pattern[pattern_ty]:
| star_pattern
| pattern

star_pattern[pattern_ty]:
star_pattern[pattern_ty] (memo):
| '*' target=pattern_capture_target {
_PyAST_MatchStar(target->v.Name.id, EXTRA) }
| '*' wildcard_pattern {
Expand Down Expand Up @@ -1312,4 +1312,4 @@ invalid_kvpair:
| a=expression !(':') {
RAISE_ERROR_KNOWN_LOCATION(p, PyExc_SyntaxError, a->lineno, a->end_col_offset - 1, a->end_lineno, -1, "':' expected after dictionary key") }
| expression ':' a='*' bitwise_or { RAISE_SYNTAX_ERROR_STARTING_FROM(a, "cannot use a starred expression in a dictionary value") }
| expression a=':' {RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "expression expected after dictionary key and ':'") }
| expression a=':' {RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "expression expected after dictionary key and ':'") }
21 changes: 21 additions & 0 deletions Lib/test/test_patma.py
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
Expand Up @@ -3151,6 +3151,27 @@ def f(command): # 0
self.assertListEqual(self._trace(f, "go x"), [1, 2, 3])
self.assertListEqual(self._trace(f, "spam"), [1, 2, 3])

def test_parser_deeply_nested_patterns(self):
# Deeply nested patterns can cause exponential backtracking when parsing.
# See gh-93671 for more information.

levels = 100

patterns = [
"A" + "(" * levels + ")" * levels,
"{1:" * levels + "1" + "}" * levels,
"[" * levels + "1" + "]" * levels,
]

for pattern in patterns:
with self.subTest(pattern):
code = inspect.cleandoc("""
match None:
case {}:
pass
""".format(pattern))
compile(code, "<string>", "exec")


if __name__ == "__main__":
"""
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-06-10-12-03-17.gh-issue-93671.idkQqG.rst
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix some exponential backtrace case happening with deeply nested sequence
patterns in match statements. Patch by Pablo Galindo
10 changes: 10 additions & 0 deletions Parser/parser.c
Show comments
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

Back | FazBrowse Home | New Git URL