Re: frame_register_unwind(): "frame != NULL" assertion failure

[Kevin Buettner <kevinb at redhat dot com>]

Here's one possible "fix" for the assertion failure.  I've come to the
conclusion that the real culprit is get_next_frame(), but, unfortunately,
the rest of gdb is not yet ready for it to return the sentinel frame.
(See the comment in the patch for more info.)  So, until it is, I propose
that we use this hack...

	* frame.c (create_sentinel_frame): Make static.  Add forward
	declaration.
	(frame_register_unwind): Add hack for converting NULL frames
	into a sentinel frame.

Index: frame.c
===================================================================
RCS file: /cvs/src/src/gdb/frame.c,v
retrieving revision 1.66
diff -u -p -r1.66 frame.c
--- frame.c	2 Feb 2003 20:31:43 -0000	1.66
+++ frame.c	13 Feb 2003 23:20:22 -0000
@@ -39,6 +39,8 @@
 #include "command.h"
 #include "gdbcmd.h"
 
+static struct frame_info * create_sentinel_frame (struct regcache *regcache);
+
 /* Flag to indicate whether backtraces should stop at main.  */
 
 static int backtrace_below_main;
@@ -180,6 +182,15 @@ frame_register_unwind (struct frame_info
   gdb_assert (realnump != NULL);
   /* gdb_assert (bufferp != NULL); */
 
+  /* Note: kevinb/2003-02-13: This is a hack.  The problem is that
+     get_next_frame() can return NULL when it really ought to be
+     returning the sentinel frame.  So, when we detect frame == NULL,
+     just use the sentinel frame instead.  
+     FIXME: Remove this hack once get_next_frame() has been fixed
+     to never return NULL.  */
+  if (frame == NULL)
+    frame = create_sentinel_frame (current_regcache);
+
   /* NOTE: cagney/2002-11-27: A program trying to unwind a NULL frame
      is broken.  There is always a frame.  If there, for some reason,
      isn't, there is some pretty busted code as it should have
@@ -429,7 +440,7 @@ frame_map_regnum_to_name (int regnum)
 
 /* Create a sentinel frame.  */
 
-struct frame_info *
+static struct frame_info *
 create_sentinel_frame (struct regcache *regcache)
 {
   struct frame_info *frame = FRAME_OBSTACK_ZALLOC (struct frame_info);