From 4fbd330fae54a9c45d4a717127aa86d75e9938d5 Mon Sep 17 00:00:00 2001 From: Philipp Stephani Date: Tue, 28 Feb 2017 22:21:37 +0100 Subject: [PATCH] Protect against an infloop in python-mode There appears to be an edge case caused by using `syntax-ppss' in a narrowed buffer during JIT lock inside of Python triple-quote strings. Unfortunately it is impossible to reproduce without manually destroying the syntactic information in the Python buffer, but it has been observed in practice. In that case it can happen that the syntax caches get sufficiently out of whack so that there appear to be overlapping strings in the buffer. As Python has no nested strings, this situation is impossible and leads to an infloop in `python-nav-end-of-statement'. Protect against this by checking whether the search for the end of the current string makes progress. * python.el (python-nav-end-of-statement): Protect against infloop. * progmodes/python-tests.el (python-tests--python-nav-end-of-statement--infloop): Add unit test. --- lisp/progmodes/python.el | 16 +++++++++++++--- test/lisp/progmodes/python-tests.el | 19 +++++++++++++++++++ 2 files changed, 32 insertions(+), 3 deletions(-) diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el index 228a4484616..2697f1a3107 100644 --- a/lisp/progmodes/python.el +++ b/lisp/progmodes/python.el @@ -1491,10 +1491,18 @@ Optional argument NOEND is internal and makes the logic to not jump to the end of line when moving forward searching for the end of the statement." (interactive "^") - (let (string-start bs-pos) + (let (string-start bs-pos (last-string-end 0)) (while (and (or noend (goto-char (line-end-position))) (not (eobp)) (cond ((setq string-start (python-syntax-context 'string)) + ;; The assertion can only fail if syntax table + ;; text properties and the `syntax-ppss' cache + ;; are somehow out of whack. This has been + ;; observed when using `syntax-ppss' during + ;; narrowing. + (cl-assert (> string-start last-string-end) + :show-args + "Overlapping strings detected") (goto-char string-start) (if (python-syntax-context 'paren) ;; Ended up inside a paren, roll again. @@ -1504,8 +1512,10 @@ of the statement." (goto-char (+ (point) (python-syntax-count-quotes (char-after (point)) (point)))) - (or (re-search-forward (rx (syntax string-delimiter)) nil t) - (goto-char (point-max))))) + (setq last-string-end + (or (re-search-forward + (rx (syntax string-delimiter)) nil t) + (goto-char (point-max)))))) ((python-syntax-context 'paren) ;; The statement won't end before we've escaped ;; at least one level of parenthesis. diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el index 1e6b867d30b..2f4c2fb849d 100644 --- a/test/lisp/progmodes/python-tests.el +++ b/test/lisp/progmodes/python-tests.el @@ -5314,6 +5314,25 @@ class SomeClass: (or enabled (hs-minor-mode -1))))) +(ert-deftest python-tests--python-nav-end-of-statement--infloop () + "Checks that `python-nav-end-of-statement' doesn't infloop in a +buffer with overlapping strings." + (python-tests-with-temp-buffer "''' '\n''' ' '\n" + (syntax-propertize (point-max)) + ;; Create a situation where strings nominally overlap. This + ;; shouldn't happen in practice, but apparently it can happen when + ;; a package calls `syntax-ppss' in a narrowed buffer during JIT + ;; lock. + (put-text-property 4 5 'syntax-table (string-to-syntax "|")) + (remove-text-properties 8 9 '(syntax-table nil)) + (goto-char 4) + (setq-local syntax-propertize-function nil) + ;; The next form should not infloop. We have to disable + ;; ‘debug-on-error’ so that ‘cl-assert’ doesn’t call the debugger. + (should-error (let ((debug-on-error nil)) + (python-nav-end-of-statement))) + (should (eolp)))) + (provide 'python-tests) -- 2.39.5