Fix minor problems found by static checking.

* buffer.c (Fdelete_all_overlays): Return nil.
* doc.c (Fsubstitute_command_keys):
* regex.c (WEAK_ALIAS):
* xdisp.c (redisplay_internal):
Move initialization down, to pacify GCC 4.7.1 -Wjump-misses-init.

src/ChangeLog

+2012-09-03  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix minor problems found by static checking.
+	* buffer.c (Fdelete_all_overlays): Return nil.
+	* doc.c (Fsubstitute_command_keys):
+	* regex.c (WEAK_ALIAS):
+	* xdisp.c (redisplay_internal):
+	Move initialization down, to pacify GCC 4.7.1 -Wjump-misses-init.
+
 2012-09-03  Martin Rudalics  <rudalics@gmx.at>
 
 	* buffer.c (Fdelete_all_overlays): New function.

src/buffer.c

@@ -4091,6 +4091,7 @@ buffer.  */)
     }
 
   delete_all_overlays (buf);
+  return Qnil;
 }
 
 /* Overlay dissection functions.  */

src/doc.c

@@ -848,9 +848,10 @@ Otherwise, return a new string, without any text properties.  */)
 	  struct buffer *oldbuf;
 	  ptrdiff_t start_idx;
 	  /* This is for computing the SHADOWS arg for describe_map_tree.  */
-	  Lisp_Object active_maps = Fcurrent_active_maps (Qnil, Qnil);
+	  Lisp_Object active_maps;
 	  Lisp_Object earlier_maps;
 
+	  active_maps = Fcurrent_active_maps (Qnil, Qnil);
 	  changed = 1;
 	  strp += 2;		/* skip \{ or \< */
 	  start = strp;

src/regex.c

@@ -5160,11 +5160,13 @@ re_match_2_internal (struct re_pattern_buffer *bufp, const re_char *string1,
 	    {
 	      /* 1 if this match ends in the same string (string1 or string2)
 		 as the best previous match.  */
-	      boolean same_str_p = (FIRST_STRING_P (match_end)
-				    == FIRST_STRING_P (d));
+	      boolean same_str_p;
 	      /* 1 if this match is the best seen so far.  */
 	      boolean best_match_p;
 
+	      same_str_p = (FIRST_STRING_P (match_end)
+			    == FIRST_STRING_P (d));
+
 	      /* AIX compiler got confused when this was combined
 		 with the previous declaration.  */
 	      if (same_str_p)

src/xdisp.c

@@ -13511,9 +13511,10 @@ redisplay_internal (void)
     }
   else if (FRAME_VISIBLE_P (sf) && !FRAME_OBSCURED_P (sf))
     {
-      Lisp_Object mini_window = FRAME_MINIBUF_WINDOW (sf);
+      Lisp_Object mini_window;
       struct frame *mini_frame;
 
+      mini_window = FRAME_MINIBUF_WINDOW (sf);
       displayed_buffer = XBUFFER (XWINDOW (selected_window)->buffer);
       /* Use list_of_error, not Qerror, so that
 	 we catch only errors and don't run the debugger.  */