bug#8512: possibly uninitialized variable in x_produce_glyphs

[Paul Eggert <eggert@cs.ucla.edu>]

In the Emacs trunk, GCC 3.4.3 on Solaris 10 warns about a possibly uninitialized
variable in x_produce_glyphs, and it's not clear to me that this diagnostic is
wrong.  The function assumes that cmp->glyph_len > 0, but a quick look through the
rest of Emacs suggests that it's possible that it's zero.  To play it safe
until someone with more expertise about glyphs can look at the problem, I plan
to install this patch:

--- src/xdisp.c	2011-04-16 01:54:37 +0000
+++ src/xdisp.c	2011-04-16 19:24:11 +0000
@@ -22712,7 +22712,7 @@ x_produce_glyphs (struct it *it)
 	  int lbearing, rbearing;
 	  int i, width, ascent, descent;
 	  int left_padded = 0, right_padded = 0;
-	  int c;
+	  int c = 0; /* FIXME: Is 0 right here, when cmp->glyph_len == 0?  */
 	  XChar2b char2b;
 	  struct font_metrics *pcm;
 	  int font_not_found_p;