Re: [rfc, frame] Always check for unsaved PC

[Daniel Jacobowitz <drow@false.org>]

On Thu, Jan 11, 2007 at 05:34:22PM +0100, Andreas Schwab wrote:
> This is broken.  You can't use PC_REGNUM unconditionally without checking
> whether that register actually exists.  The ia64 does not have such a
> register.

I assume it causes trouble there.  Sorry.  Does this help (untested)?

-- 
Daniel Jacobowitz
CodeSourcery

2007-01-11  Daniel Jacobowitz  <dan@codesourcery.com>

	* frame.c (get_prev_frame_1): Check PC_REGNUM before using it.

Index: frame.c
===================================================================
RCS file: /cvs/src/src/gdb/frame.c,v
retrieving revision 1.218
diff -u -p -r1.218 frame.c
--- frame.c	9 Jan 2007 20:19:15 -0000	1.218
+++ frame.c	11 Jan 2007 16:44:40 -0000
@@ -1221,10 +1221,17 @@ get_prev_frame_1 (struct frame_info *thi
      have different frame IDs, the new frame will be bogus; two
      functions can't share a register save slot for the PC.  This can
      happen when the prologue analyzer finds a stack adjustment, but
-     no PC save.  This check does assume that the "PC register" is
-     roughly a traditional PC, even if the gdbarch_unwind_pc method
-     frobs it.  */
+     no PC save.
+
+     This check does assume that the "PC register" is roughly a
+     traditional PC, even if the gdbarch_unwind_pc method adjusts
+     it (we do not rely on the value, only on the unwound PC being
+     dependent on this value).  A potential improvement would be
+     to have the frame prev_pc method and the gdbarch unwind_pc
+     method set the same lval and location information as
+     frame_register_unwind.  */
   if (this_frame->level > 0
+      && PC_REGNUM >= 0
       && get_frame_type (this_frame) == NORMAL_FRAME
       && get_frame_type (this_frame->next) == NORMAL_FRAME)
     {