Bug description:
state_reset() in Modules/_sre/sre.c clears the per-match state at the start of each match in a scanner loop, including state->repeat, but not state->save_marks, which is zeroed only in state_init(). A match aborted by a signal returns straight out of SRE(match), so that counter stays above zero for the rest of the iterator and every later match saves and restores marks on backtracking that it would otherwise skip. Only finditer() and pattern.scanner() can observe it, because the findall/sub/split loops abandon the state on error. Results are unchanged, only the cost.
$ cat repro.py
import re, signal, time
class Alarm(Exception): pass
def boom(*args): raise Alarm
signal.signal(signal.SIGALRM, boom)
PAT = r"(z)*" + "(a)" * 200 + r"(?:xy|x)" * 300
SUBJECT = "z" * 400000 + ("a" * 200 + "x" * 300) * 400
def run(interrupt):
it = re.compile(PAT).finditer(SUBJECT)
if interrupt:
signal.setitimer(signal.ITIMER_REAL, 0.02)
try:
next(it)
except Alarm:
pass
signal.setitimer(signal.ITIMER_REAL, 0)
next(it)
t = time.perf_counter()
spans = [m.span() for m in it]
return time.perf_counter() - t, spans
clean, clean_spans = run(False)
dirty, dirty_spans = run(True)
print("clean iterator : %.4fs, %d matches" % (clean, len(clean_spans)))
print("resumed after one abort : %.4fs, %d matches" % (dirty, len(dirty_spans)))
print("same results : %s" % (clean_spans == dirty_spans,))
$ ./python repro.py
clean iterator : 0.0087s, 399 matches
resumed after one abort : 0.0238s, 399 matches
same results : True
Expected: an iterator resumed after an aborted match costs the same as a clean one.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Linked PRs
Bug description:
state_reset()inModules/_sre/sre.cclears the per-match state at the start of each match in a scanner loop, includingstate->repeat, but notstate->save_marks, which is zeroed only instate_init(). A match aborted by a signal returns straight out ofSRE(match), so that counter stays above zero for the rest of the iterator and every later match saves and restores marks on backtracking that it would otherwise skip. Onlyfinditer()andpattern.scanner()can observe it, because thefindall/sub/splitloops abandon the state on error. Results are unchanged, only the cost.Expected: an iterator resumed after an aborted match costs the same as a clean one.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Linked PRs