RFC: partially fix empty DW_OP_piece

[Tom Tromey]

>>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:

Jan> OK, that probably means there really must remain a way to convert
Jan> `inferior dependent struct value' into an `inferior independent
Jan> struct value'.

Yeah, at least as far as the bounds are concerned.  IMO.

The current gdb model is sort of mixed.  A struct value is a snapshot of
some bit of state.  But, when printing a value, we might refer to other
state in the target.  For example:

    struct x { char *name; };

If we have a value of that type, gdb will try to dereference the pointer
when printing.  But, we make no attempt to save this memory alongside
the value somewhere.  So, if you have a complicated debug session and
then after many re-runs or whatever do "print $1", you can get weird
answers.

There may be some other odd cases, too.

We could fix this, of course, but it isn't clear that it is worth the
effort.

Tom