Re: RFA: Prologue cache fix

[Andrew Cagney <ac131313 at cygnus dot com>]

Fernando Nasser wrote:
> 
> This patch fixes a problem that happens when gdb reconnects to a
> target.  Targets that have a prologue cache must invalidate its contents
> or they can assume wrong things based on stale data.

I'm wondering when exactly this prologue_cache provides real benefit?

If the prologue_cache is purged at the same time as the frame obstack
then the two have the same lifetime.  If that is the case then I think
that the prologue analysis might as well be left in the frame object in
``struct frame_extra_info''.

The only other possibility I can think of is is something like an
inferior function call where GDB comes back to that exact same address. 
For a recursive call, the register info would be wrong.

So anyone enlighten me as to when exactly this thing kicks in? :-)

> 2000-02-23  Fernando Nasser  <fnasser@totem.to.cygnus.com>
> 
>         * gdbint.texinfo: Add entry for target dependent macro
>         FLUSH_PROLOGUE_CACHE.

> *** blockframe.c        1999/12/22 21:45:03     1.1.1.11
> --- blockframe.c        2000/02/23 00:17:15
> *************** flush_cached_frames ()
> *** 269,274 ****
> --- 269,277 ----
> 
>     current_frame = NULL;               /* Invalidate cache */
>     select_frame (NULL, -1);
> + #ifdef FLUSH_PROLOGUE_CACHE
> +   FLUSH_PROLOGUE_CACHE ();
> + #endif
>     annotate_frames_invalid ();
>   }
>

As an asside, this won't work well with multi-arch.

	enjoy,
		Andrew