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PR 13471: Add cycle-detection during lex-abbrev expansion to raise appropriate syntax error.

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Also add test cases for lex-abbrev cycle detection.

original commit: 7146289c34c8256e54bda9157fcdc337047ae043
tokens
Danny Yoo 12 years ago
parent ec6cb60c00
commit c6375182fa
2 changed files with 143 additions and 99 deletions
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29
collects/parser-tools/private-lex/error-tests.rkt
Unescape Escape View File

@ -40,6 +40,35 @@
(let () (let ()
(lexer ((a) 1)))))) (lexer ((a) 1))))))
;; Detecting mutual recursion cycle:
(check-regexp-match #rx"regular-expression"
(catch-syn-error
(let ()
(define-lex-abbrev a b)
(define-lex-abbrev b a)
(let ()
(lexer ((a) 1))))))
(check-regexp-match #rx"regular-expression"
(catch-syn-error
(let ()
(define-lex-abbrev a (repetition 0 1 b))
(define-lex-abbrev b (repetition 0 1 a))
(let ()
(lexer ((a) 1))))))
;; Detecting cycle within same abbreviation:
(check-regexp-match #rx"regular-expression"
(catch-syn-error
(let ()
(define-lex-abbrev balanced
(union (concatenation "(" balanced ")" balanced)
any-char))
(lexer
[balanced (string-append lexeme (balanced input-port))]
[(eof) ""]))))
(check-regexp-match #rx"regular-expression" (catch-syn-error (lexer (1 1)))) (check-regexp-match #rx"regular-expression" (catch-syn-error (lexer (1 1))))
(check-regexp-match #rx"repetition" (catch-syn-error (lexer ((repetition) 1)))) (check-regexp-match #rx"repetition" (catch-syn-error (lexer ((repetition) 1))))
(check-regexp-match #rx"repetition" (catch-syn-error (lexer ((repetition #\1 #\1 "3") 1)))) (check-regexp-match #rx"repetition" (catch-syn-error (lexer ((repetition #\1 #\1 "3") 1))))

45
collects/parser-tools/private-lex/stx.rkt
Unescape Escape View File

@ -1,6 +1,6 @@
(module stx mzscheme (module stx mzscheme
(require syntax/boundmap (require "util.rkt"
"util.rkt") syntax/id-table)
(provide parse) (provide parse)
@ -37,10 +37,18 @@
;; checks for errors and generates the plain s-exp form for s ;; checks for errors and generates the plain s-exp form for s
;; Expands lex-abbrevs and applies lex-trans. ;; Expands lex-abbrevs and applies lex-trans.
(define (parse stx disappeared-uses) (define (parse stx disappeared-uses)
(let ((parse (let loop ([stx stx]
(lambda (s) [disappeared-uses disappeared-uses]
(parse (syntax-rearm s stx) ;; seen-lex-abbrevs: id-table
disappeared-uses)))) [seen-lex-abbrevs (make-immutable-free-id-table)])
(let ([recur (lambda (s)
(loop (syntax-rearm s stx)
disappeared-uses
seen-lex-abbrevs))]
[recur/abbrev (lambda (s id)
(loop (syntax-rearm s stx)
disappeared-uses
(free-id-table-set seen-lex-abbrevs id id)))])
(syntax-case (disarm stx) (repetition union intersection complement concatenation (syntax-case (disarm stx) (repetition union intersection complement concatenation
char-range char-complement) char-range char-complement)
(_ (_
@ -50,8 +58,15 @@
(raise-syntax-error 'regular-expression (raise-syntax-error 'regular-expression
"undefined abbreviation" "undefined abbreviation"
stx)) stx))
;; Check for cycles.
(when (free-id-table-ref seen-lex-abbrevs stx (lambda () #f))
(raise-syntax-error 'regular-expression
"illegal lex-abbrev cycle detected"
stx
#f
(list (free-id-table-ref seen-lex-abbrevs stx))))
(set-box! disappeared-uses (cons stx (unbox disappeared-uses))) (set-box! disappeared-uses (cons stx (unbox disappeared-uses)))
(parse ((lex-abbrev-get-abbrev expansion))))) (recur/abbrev ((lex-abbrev-get-abbrev expansion)) stx)))
(_ (_
(or (char? (syntax-e stx)) (string? (syntax-e stx))) (or (char? (syntax-e stx)) (string? (syntax-e stx)))
(syntax-e stx)) (syntax-e stx))
@ -78,18 +93,18 @@
#f #f
"the first argument is not less than or equal to the second argument" "the first argument is not less than or equal to the second argument"
stx)) stx))
`(repetition ,low ,high ,(parse re))))) `(repetition ,low ,high ,(recur re)))))
((union re ...) ((union re ...)
`(union ,@(map parse (syntax->list (syntax (re ...)))))) `(union ,@(map recur (syntax->list (syntax (re ...))))))
((intersection re ...) ((intersection re ...)
`(intersection ,@(map parse (syntax->list (syntax (re ...)))))) `(intersection ,@(map recur (syntax->list (syntax (re ...))))))
((complement re ...) ((complement re ...)
(let ((re-list (syntax->list (syntax (re ...))))) (let ((re-list (syntax->list (syntax (re ...)))))
(unless (= 1 (length re-list)) (unless (= 1 (length re-list))
(bad-args stx 1)) (bad-args stx 1))
`(complement ,(parse (car re-list))))) `(complement ,(recur (car re-list)))))
((concatenation re ...) ((concatenation re ...)
`(concatenation ,@(map parse (syntax->list (syntax (re ...)))))) `(concatenation ,@(map recur (syntax->list (syntax (re ...))))))
((char-range arg ...) ((char-range arg ...)
(let ((arg-list (syntax->list (syntax (arg ...))))) (let ((arg-list (syntax->list (syntax (arg ...)))))
(unless (= 2 (length arg-list)) (unless (= 2 (length arg-list))
@ -106,7 +121,7 @@
(let ((arg-list (syntax->list (syntax (arg ...))))) (let ((arg-list (syntax->list (syntax (arg ...)))))
(unless (= 1 (length arg-list)) (unless (= 1 (length arg-list))
(bad-args stx 1)) (bad-args stx 1))
(let ((parsed (parse (car arg-list)))) (let ((parsed (recur (car arg-list))))
(unless (char-set? parsed) (unless (char-set? parsed)
(raise-syntax-error #f (raise-syntax-error #f
"not a character set" "not a character set"
@ -120,7 +135,7 @@
(set-box! disappeared-uses (cons o (unbox disappeared-uses))) (set-box! disappeared-uses (cons o (unbox disappeared-uses)))
(cond (cond
((lex-trans? expansion) ((lex-trans? expansion)
(parse ((lex-trans-f expansion) (disarm stx)))) (recur ((lex-trans-f expansion) (disarm stx))))
(expansion (expansion
(raise-syntax-error 'regular-expression (raise-syntax-error 'regular-expression
"not a lex-trans" "not a lex-trans"
@ -133,7 +148,7 @@
(raise-syntax-error (raise-syntax-error
'regular-expression 'regular-expression
"not a char, string, identifier, or (op args ...)" "not a char, string, identifier, or (op args ...)"
stx))))) stx))))))

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