* xterm.c (x_draw_underwave): Check for integer overflow.

This pacifies gcc 4.7.0 -Wunsafe-loop-optimizations on x86-64.

src/ChangeLog

@@ -1,3 +1,8 @@
+2012-06-17  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* xterm.c (x_draw_underwave): Check for integer overflow.
+	This pacifies gcc 4.7.0 -Wunsafe-loop-optimizations on x86-64.
+
 2012-06-17  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* nsterm.m (x_free_frame_resources): Move xfree so freed memory isn't

src/xterm.c

@@ -2710,6 +2710,9 @@ x_draw_underwave (struct glyph_string *s)
   else
     y2 += dy;
 
+  if (INT_MAX - dx < xmax)
+    abort ();
+
   while (x1 <= xmax)
     {
       XDrawLine (s->display, s->window, s->gc, x1, y1, x2, y2);