[commit] Fix ARM valid PC check

[Daniel Jacobowitz]

Comparing get_frame_func to lowest_pc (usually 0x200, 0x8000, or
thereabouts) means that we were never backtracing past a function
without symbols because an invalid function is represented as
zero.  Generally this does not matter as we will not know how anyway,
but I have a heuristic patch that does OK and this broke it.

Tested extensively on arm-symbianelf, checked in.

-- 
Daniel Jacobowitz
CodeSourcery

2008-05-02  Daniel Jacobowitz  <dan@codesourcery.com>

	* arm-tdep.c (arm_prologue_this_id): Compare pc, not func, to
	lowest_pc.

Index: arm-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.c,v
retrieving revision 1.262
diff -u -p -r1.262 arm-tdep.c
--- arm-tdep.c	2 May 2008 16:00:35 -0000	1.262
+++ arm-tdep.c	2 May 2008 17:23:14 -0000
@@ -981,23 +981,22 @@ arm_prologue_this_id (struct frame_info 
 {
   struct arm_prologue_cache *cache;
   struct frame_id id;
-  CORE_ADDR func;
+  CORE_ADDR pc, func;
 
   if (*this_cache == NULL)
     *this_cache = arm_make_prologue_cache (this_frame);
   cache = *this_cache;
 
-  func = get_frame_func (this_frame);
-
-  /* This is meant to halt the backtrace at "_start".  Make sure we
-     don't halt it at a generic dummy frame. */
-  if (func <= gdbarch_tdep (get_frame_arch (this_frame))->lowest_pc)
+  /* This is meant to halt the backtrace at "_start".  */
+  pc = get_frame_pc (this_frame);
+  if (pc <= gdbarch_tdep (get_frame_arch (this_frame))->lowest_pc)
     return;
 
   /* If we've hit a wall, stop.  */
   if (cache->prev_sp == 0)
     return;
 
+  func = get_frame_func (this_frame);
   id = frame_id_build (cache->prev_sp, func);
   *this_id = id;
 }