gdb/
* value.h (value_bytes_available): Declare.
(mark_value_bytes_unavailable): Declare.
* value.c (struct range): New struct.
(range_s): New typedef.
(ranges_overlap): New function.
(range_lessthan): New function.
(ranges_contain_p): New function.
(struct value) <unavailable>: New field.
(value_bytes_available): New function.
(mark_value_bytes_unavailable): New function.
(require_not_optimized_out): Constify parameter.
(require_available): New function.
(value_contents_all, value_contents): Require all bytes be
available.
(value_free): Free `unavailable'.
(value_copy): Copy `unavailable'.
* valprint.h (val_print_unavailable): Declare.
* valprint.c (valprint_check_validity): Rename `offset' parameter
to `embedded_offset'. If printing a scalar, check whether the
value chunk is available.
(val_print_unavailable): New.
(val_print_scalar_formatted): Check whether the value is
available.
* python/py-prettyprint.c (apply_val_pretty_printer): Refuse
pretty-printing unavailable values.