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bug#63535: Master branch: Error in forw_comment (syntax.c) handling of e
From: |
Alan Mackenzie |
Subject: |
bug#63535: Master branch: Error in forw_comment (syntax.c) handling of escaped LFs |
Date: |
Tue, 16 May 2023 14:03:18 +0000 |
On Tue, May 16, 2023 at 10:57:40 +0000, Alan Mackenzie wrote:
> Hello, Emacs.
> In the master branch:
> Consider the following C++ Mode buffer:
> // comment \
> comment line 2
> line_3();
> .. The backslash at the end of line 1 extends the comment into line 2.
> Put point at // on L1, and do:
> M-: (setq s (parse-partial-sexp (point) (+ (point) 9)))
> .. s gets the parse state of the inside of the comment.
> Now put point at EOL 1, between the backslash and the LF. Do
> M-: (parse-partial-sexp (point) (point-max) nil nil s 'syntax-table)
> .. This ought to leave point at BOL 2, since the syntax before the LF at
> EOL 1 is that of a C++ comment, otherwise neutral. Instead, it leaves
> point wrongly at BOL 3.
> #########################################################################
> The reason for this bug is at L+42 of forw_comment (in syntax.c). There
> we have
> && !(comment_end_can_be_escaped && char_quoted (from, from_byte))
> .. Checking char_quoted is wrong. Instead the function should check the
> current parse state.
And here is a patch which fixes it. I will apply this patch to master
soon if I don't hear any objection.
diff --git a/src/syntax.c b/src/syntax.c
index e9e04e2d638..76d9f16e4ed 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2344,7 +2344,9 @@ forw_comment (ptrdiff_t from, ptrdiff_t from_byte,
ptrdiff_t stop,
&& SYNTAX_FLAGS_COMMENT_STYLE (syntax, 0) == style
&& (SYNTAX_FLAGS_COMMENT_NESTED (syntax) ?
(nesting > 0 && --nesting == 0) : nesting < 0)
- && !(comment_end_can_be_escaped && char_quoted (from, from_byte)))
+ && !(comment_end_can_be_escaped &&
+ (((prev_syntax & 0xff) == Sescape)
+ || ((prev_syntax & 0xff) == Scharquote))))
/* We have encountered a comment end of the same style
as the comment sequence which began this comment
section. */
--
Alan Mackenzie (Nuremberg, Germany).
bug#63535: Master branch: Error in forw_comment (syntax.c) handling of escaped LFs, Eli Zaretskii, 2023/05/16