From: Eli Zaretskii <eliz@gnu.org>
Date: Wed, 27 Aug 2014 19:40:54 +0000 (+0300)
Subject: Fix bug #18339 with segfault when $ is typed into empty LaTeX buffer.
X-Git-Tag: emacs-25.0.90~2635^2~679^2~419
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=9bac5fd91f5012a682be13e16561671f0f01c941;p=emacs.git

Fix bug #18339 with segfault when $ is typed into empty LaTeX buffer.

 src/syntax.c (scan_lists): Don't examine positions before BEGV.
---

diff --git a/src/ChangeLog b/src/ChangeLog
index 8a32bc27b0b..a7c8cb59a0f 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2014-08-27  Eli Zaretskii  <eliz@gnu.org>
+
+	* syntax.c (scan_lists): Don't examine positions before BEGV.
+	(Bug#18339)
+
 2014-08-27  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Improve robustness of new string-collation code (Bug#18051).
diff --git a/src/syntax.c b/src/syntax.c
index 4166ee211c7..df8800e90be 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2857,10 +2857,13 @@ scan_lists (EMACS_INT from, EMACS_INT count, EMACS_INT depth, bool sexpflag)
 	    case Smath:
 	      if (!sexpflag)
 		break;
-	      temp_pos = dec_bytepos (from_byte);
-	      UPDATE_SYNTAX_TABLE_BACKWARD (from - 1);
-	      if (from != stop && c == FETCH_CHAR_AS_MULTIBYTE (temp_pos))
-		DEC_BOTH (from, from_byte);
+	      if (from > BEGV)
+		{
+		  temp_pos = dec_bytepos (from_byte);
+		  UPDATE_SYNTAX_TABLE_BACKWARD (from - 1);
+		  if (from != stop && c == FETCH_CHAR_AS_MULTIBYTE (temp_pos))
+		    DEC_BOTH (from, from_byte);
+		}
 	      if (mathexit)
 		{
 		  mathexit = 0;