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gh-153169: Look through marks in the regex alternation quick check #153170

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gh-153169: Look through marks in the regex alternation quick check #153170

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gh-153169: Look through marks in the regex alternation quick check
serhiy-storchaka Jul 6, 2026
a47c55f
Merge remote-tracking branch 'upstream/main' into sre-branch-peek
serhiy-storchaka Jul 6, 2026
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-07-06-18-00-00.gh-issue-153169.QkChk1.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Speed up matching of regular expression alternations whose alternatives
start with a capturing group or with a repeat with a nonzero minimum:
such alternatives can now be skipped without entering them when their
first character cannot match.
36 changes: 36 additions & 0 deletions Modules/_sre/sre_lib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -875,6 +875,42 @@ SRE(match)(SRE_STATE* state, const SRE_CODE* pattern, int toplevel)
!SRE(charset)(state, pattern + 3,
(SRE_CODE) *ptr)))
continue;
if (pattern[1] == SRE_OP_MARK) {
/* the quick checks above also apply behind group marks
and to a repeat of one item with a nonzero minimum */
const SRE_CODE *alt = pattern + 1;
do {
alt += 2;
} while (alt[0] == SRE_OP_MARK);
if ((alt[0] == SRE_OP_REPEAT_ONE ||
alt[0] == SRE_OP_MIN_REPEAT_ONE ||
alt[0] == SRE_OP_POSSESSIVE_REPEAT_ONE) &&
alt[2] > 0)
alt += 4;
if (alt[0] == SRE_OP_LITERAL &&
(ptr >= end ||
(SRE_CODE) *ptr != alt[1]))
continue;
if (alt[0] == SRE_OP_IN &&
(ptr >= end ||
!SRE(charset)(state, alt + 2,
(SRE_CODE) *ptr)))
continue;
}
else if ((pattern[1] == SRE_OP_REPEAT_ONE ||
pattern[1] == SRE_OP_MIN_REPEAT_ONE ||
pattern[1] == SRE_OP_POSSESSIVE_REPEAT_ONE) &&
pattern[3] > 0) {
if (pattern[5] == SRE_OP_LITERAL &&
(ptr >= end ||
(SRE_CODE) *ptr != pattern[6]))
continue;
if (pattern[5] == SRE_OP_IN &&
(ptr >= end ||
!SRE(charset)(state, pattern + 7,
(SRE_CODE) *ptr)))
continue;
}
state->ptr = ptr;
DO_JUMP(JUMP_BRANCH, jump_branch, pattern+1);
if (ret) {
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