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authorEli Zaretskii <eliz@gnu.org>2020-09-19 19:54:01 +0300
committerEli Zaretskii <eliz@gnu.org>2020-09-19 19:54:01 +0300
commitdf04f3e755f3001ebb9cc428faa7fa46059e636b (patch)
treeacf478dc8aca3749f10ad6f9d5527cc29b05ed4c
parentfd1fe1e1ecb6c68bbdea4bf071166779388174d0 (diff)
downloademacs-df04f3e755f3001ebb9cc428faa7fa46059e636b.tar.gz
Fix a rare segfault in syntax.c
* src/syntax.c (Fforward_comment): Prevent the loop for COUNT < 0 from going outside the valid range of character/byte positions. (Bug#43499) * doc/lispref/syntax.texi (Syntax Class Table): Mention the "comment-fence" and "string-fence" as alternative names of 2 syntax classes.
-rw-r--r--doc/lispref/syntax.texi18
-rw-r--r--src/syntax.c25
2 files changed, 24 insertions, 19 deletions
diff --git a/doc/lispref/syntax.texi b/doc/lispref/syntax.texi
index b3c77665bae..b99b5de0b31 100644
--- a/doc/lispref/syntax.texi
+++ b/doc/lispref/syntax.texi
@@ -256,10 +256,11 @@ look in the standard syntax table to find the syntax of this
character.
@item Generic comment delimiters: @samp{!}
-Characters that start or end a special kind of comment. @emph{Any}
-generic comment delimiter matches @emph{any} generic comment
-delimiter, but they cannot match a comment starter or comment ender;
-generic comment delimiters can only match each other.
+(This syntax class is also known as ``comment-fence''.) Characters
+that start or end a special kind of comment. @emph{Any} generic
+comment delimiter matches @emph{any} generic comment delimiter, but
+they cannot match a comment starter or comment ender; generic comment
+delimiters can only match each other.
This syntax class is primarily meant for use with the
@code{syntax-table} text property (@pxref{Syntax Properties}). You
@@ -268,10 +269,11 @@ first and last characters of the range @code{syntax-table} properties
identifying them as generic comment delimiters.
@item Generic string delimiters: @samp{|}
-Characters that start or end a string. This class differs from the
-string quote class in that @emph{any} generic string delimiter can
-match any other generic string delimiter; but they do not match
-ordinary string quote characters.
+(This syntax class is also known as ``string-fence''.) Characters
+that start or end a string. This class differs from the string quote
+class in that @emph{any} generic string delimiter can match any other
+generic string delimiter; but they do not match ordinary string quote
+characters.
This syntax class is primarily meant for use with the
@code{syntax-table} text property (@pxref{Syntax Properties}). You
diff --git a/src/syntax.c b/src/syntax.c
index a79ab863367..e8b32f5a445 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2545,20 +2545,23 @@ between them, return t; otherwise return nil. */)
bool fence_found = 0;
ptrdiff_t ini = from, ini_byte = from_byte;
- while (1)
+ if (from > stop)
{
- DEC_BOTH (from, from_byte);
- UPDATE_SYNTAX_TABLE_BACKWARD (from);
- c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
- if (SYNTAX (c) == Scomment_fence
- && !char_quoted (from, from_byte))
+ while (1)
{
- fence_found = 1;
- break;
+ DEC_BOTH (from, from_byte);
+ UPDATE_SYNTAX_TABLE_BACKWARD (from);
+ c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
+ if (SYNTAX (c) == Scomment_fence
+ && !char_quoted (from, from_byte))
+ {
+ fence_found = 1;
+ break;
+ }
+ else if (from == stop)
+ break;
+ rarely_quit (++quit_count);
}
- else if (from == stop)
- break;
- rarely_quit (++quit_count);
}
if (fence_found == 0)
{