[ob] Fix valgrind warnings for amd64

[Daniel Jacobowitz]

If you start GDB with an amd64 binary and set a breakpoint, valgrind
spews out a few pages of errors.  It was not easy to track this down,
since valgrind is not very helpful about conditional moves - it does
not consider them to be a control transfer, so the warning doesn't
appear until much later on.

Anyway, the problem was "if (cache.frameless_p)" in
amd64_skip_prologue.  The other two uses of a cache zalloc it and set
defaults, but that one didn't.  The obvious fix is to use the same
initialization code; memset would not be right since frameless_p
should default to 1.

Tested on amd64-linux, no changes, and committed.

-- 
Daniel Jacobowitz
CodeSourcery

2007-03-27  Daniel Jacobowitz  <dan@codesourcery.com>

	* amd64-tdep.c (amd64_init_frame_cache): New function.
	(amd64_alloc_frame_cache, amd64_skip_prologue): Use it.

--- amd64-tdep.c	(revision 348)
+++ amd64-tdep.c	(local)
@@ -726,16 +726,13 @@ struct amd64_frame_cache
   int frameless_p;
 };
 
-/* Allocate and initialize a frame cache.  */
+/* Initialize a frame cache.  */
 
-static struct amd64_frame_cache *
-amd64_alloc_frame_cache (void)
+static void
+amd64_init_frame_cache (struct amd64_frame_cache *cache)
 {
-  struct amd64_frame_cache *cache;
   int i;
 
-  cache = FRAME_OBSTACK_ZALLOC (struct amd64_frame_cache);
-
   /* Base address.  */
   cache->base = 0;
   cache->sp_offset = -8;
@@ -749,7 +746,17 @@ amd64_alloc_frame_cache (void)
 
   /* Frameless until proven otherwise.  */
   cache->frameless_p = 1;
+}
 
+/* Allocate and initialize a frame cache.  */
+
+static struct amd64_frame_cache *
+amd64_alloc_frame_cache (void)
+{
+  struct amd64_frame_cache *cache;
+
+  cache = FRAME_OBSTACK_ZALLOC (struct amd64_frame_cache);
+  amd64_init_frame_cache (cache);
   return cache;
 }
 
@@ -810,6 +817,7 @@ amd64_skip_prologue (CORE_ADDR start_pc)
   struct amd64_frame_cache cache;
   CORE_ADDR pc;
 
+  amd64_init_frame_cache (&cache);
   pc = amd64_analyze_prologue (start_pc, 0xffffffffffffffffLL, &cache);
   if (cache.frameless_p)
     return start_pc;