suzanne.soy/compatibility
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Disallow greedy quantifiers from having empty operands in order to stave off

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infinite loops.

original commit: d9c96724bdb2425e802a3360ceaa7ba4f02ab679
This commit is contained in:
Dorai Sitaram 2005-04-25 15:52:34 +00:00
parent 4836b4c50e
commit 372146cde9
1 changed files with 17 additions and 2 deletions
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19
collects/mzlib/pregexp.ss
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@ -520,10 +520,20 @@
(let* ((maximal? (not (cadr re))) (let* ((maximal? (not (cadr re)))
(p (caddr re)) (p (caddr re))
(q (cadddr re)) (q (cadddr re))
(could-loop-infinitely? (and maximal? (not q)))
(re (car (cddddr re)))) (re (car (cddddr re))))
(let loup-p ((k 0) (i i)) (let loup-p ((k 0) (i i))
(if (< k p) (if (< k p)
(sub re i (lambda (i1) (loup-p (+ k 1) i1)) fk) (sub
re
i
(lambda (i1)
(if (and could-loop-infinitely? (= i1 i))
(error
'pregexp-match-positions-aux
'greedy-quantifier-operand-could-be-empty))
(loup-p (+ k 1) i1))
fk)
(let ((q (and q (- q p)))) (let ((q (and q (- q p))))
(let loup-q ((k 0) (i i)) (let loup-q ((k 0) (i i))
(let ((fk (lambda () (sk i)))) (let ((fk (lambda () (sk i))))
@ -533,7 +543,12 @@
(sub (sub
re re
i i
(lambda (i1) (or (loup-q (+ k 1) i1) (fk))) (lambda (i1)
(if (and could-loop-infinitely? (= i1 i))
(error
'pregexp-match-positions-aux
'greedy-quantifier-operand-could-be-empty))
(or (loup-q (+ k 1) i1) (fk)))
fk) fk)
(or (fk) (or (fk)
(sub (sub