RFC: selected frame in read_var_value

[Andrew Cagney]

>> For 6.0, scares the peverbial out of me -> got a convincing argument? 
>> :-)  For the mainline, not phased.
> 
> 
> Hey Andrew,
> 
> This is something I dropped the ball on.  Of course, we're a lot closer
> to releasing 6.1 now than we were when I asked you about this in
> September.  How would you feel about doing it now?  If you're
> uncomfortable, I'll try to dig up the specific instances Debian users
> have reported as causing crashes, instead.
> 
> For reference, here's the function:
> 
> struct frame_info *
> deprecated_safe_get_selected_frame (void)
> {
>   if (!target_has_registers || !target_has_stack || !target_has_memory)
>     return NULL;
>   return get_selected_frame ();
> }

Like I said, not phased (MichaelC might be though :-).

Suggest adding a note mentioning that the underlying problem is that 
some code requires both the static (or compile time) scope (identifiable 
by the SAL or a fake static-frame) when there is no dynamic (or runtime) 
scope available.  There's a discussion of this on gdb@ but my link is 
down :-(

Andrew