bug#12196: 24.1.50; setting cache-long-line-scans to non-nil freezes Emacs

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 17 Sep 2012 21:38:35 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 12196@debbugs.gnu.org
> 
> > From: Christopher Schmidt <christopher@ch.ristopher.com>
> > Cc: Eli Zaretskii <eliz@gnu.org>
> > Date: Mon, 17 Sep 2012 18:17:48 +0100 (BST)
> > 
> >     emacs -q
> >     M-: (setq-default cache-long-line-scans t) RET
> >     M-: (setq gnus-select-method
> >             '(nntp "news.gmane.org"
> >                    (nntp-open-connection-function nntp-open-tls-stream)
> >                    (nntp-port-number "nntps"))) RET
> >     M-x gnus RET
> >     ^
> >     # Move point to "{nntp:news.gmane.org} (opened)"
> >     RET
> >     # Move point to "K  XXXXX: gmane.emacs.bugs"
> >     RET RET
> 
> OK, I succeeded in reproducing this on one of the systems where I can
> debug it, thanks.

Should be fixed in trunk revision 110079, the patch is below for your
convenience.  Please test.

=== modified file 'src/ChangeLog'
--- src/ChangeLog	2012-09-17 07:56:20 +0000
+++ src/ChangeLog	2012-09-17 20:11:34 +0000
@@ -1,5 +1,9 @@
 2012-09-17  Eli Zaretskii  <eliz@gnu.org>
 
+	* search.c (scan_buffer): Use character positions in calls to
+	region_cache_forward and region_cache_backward, not byte
+	positions.  (Bug#12196)
+
 	* w32term.c (w32_read_socket): Set pending_signals to 1, like
 	xterm.c does.  Reported by Daniel Colascione <dancol@dancol.org>.
 

=== modified file 'src/search.c'
--- src/search.c	2012-09-15 07:06:56 +0000
+++ src/search.c	2012-09-17 20:11:34 +0000
@@ -674,7 +674,7 @@ scan_buffer (register int target, ptrdif
            obstacle --- the last character the dumb search loop should
            examine.  */
 	ptrdiff_t ceiling_byte = CHAR_TO_BYTE (end) - 1;
-	ptrdiff_t start_byte = CHAR_TO_BYTE (start);
+	ptrdiff_t start_byte;
 	ptrdiff_t tem;
 
         /* If we're looking for a newline, consult the newline cache
@@ -684,18 +684,22 @@ scan_buffer (register int target, ptrdif
             ptrdiff_t next_change;
             immediate_quit = 0;
             while (region_cache_forward
-                   (current_buffer, newline_cache, start_byte, &next_change))
-              start_byte = next_change;
+                   (current_buffer, newline_cache, start, &next_change))
+              start = next_change;
             immediate_quit = allow_quit;
 
+	    start_byte = CHAR_TO_BYTE (start);
+
             /* START should never be after END.  */
             if (start_byte > ceiling_byte)
               start_byte = ceiling_byte;
 
             /* Now the text after start is an unknown region, and
                next_change is the position of the next known region. */
-            ceiling_byte = min (next_change - 1, ceiling_byte);
+            ceiling_byte = min (CHAR_TO_BYTE (next_change) - 1, ceiling_byte);
           }
+	else
+	  start_byte = CHAR_TO_BYTE (start);
 
         /* The dumb loop can only scan text stored in contiguous
            bytes. BUFFER_CEILING_OF returns the last character
@@ -747,7 +751,7 @@ scan_buffer (register int target, ptrdif
       {
         /* The last character to check before the next obstacle.  */
 	ptrdiff_t ceiling_byte = CHAR_TO_BYTE (end);
-	ptrdiff_t start_byte = CHAR_TO_BYTE (start);
+	ptrdiff_t start_byte;
 	ptrdiff_t tem;
 
         /* Consult the newline cache, if appropriate.  */
@@ -756,18 +760,22 @@ scan_buffer (register int target, ptrdif
             ptrdiff_t next_change;
             immediate_quit = 0;
             while (region_cache_backward
-                   (current_buffer, newline_cache, start_byte, &next_change))
-              start_byte = next_change;
+                   (current_buffer, newline_cache, start, &next_change))
+              start = next_change;
             immediate_quit = allow_quit;
 
+	    start_byte = CHAR_TO_BYTE (start);
+
             /* Start should never be at or before end.  */
             if (start_byte <= ceiling_byte)
               start_byte = ceiling_byte + 1;
 
             /* Now the text before start is an unknown region, and
                next_change is the position of the next known region. */
-            ceiling_byte = max (next_change, ceiling_byte);
+            ceiling_byte = max (CHAR_TO_BYTE (next_change), ceiling_byte);
           }
+	else
+	  start_byte = CHAR_TO_BYTE (start);
 
         /* Stop scanning before the gap.  */
 	tem = BUFFER_FLOOR_OF (start_byte - 1);