print PTR.all where PTR is an Ada thin pointer

print PTR.all where PTR is an Ada thin pointer

Consider the following declaration:

   type Array_Type is array (Natural range <>) of Integer;
   type Array_Ptr is access all Array_Type;
   for Array_Ptr'Size use 64;
   Three_Ptr : Array_Ptr := new Array_Type'(1 => 1, 2 => 2, 3 => 3);

This creates a pointer to an array where the bounds are stored
in a memory region just before the array itself (aka a "thin pointer").
In DWARF, this is described as a the usual pointer type to an array
whose subrange has dynamic values for its bounds:

    <1><25>: Abbrev Number: 4 (DW_TAG_array_type)
       <26>   DW_AT_name        : foo__array_type
    [...]
    <2><3b>: Abbrev Number: 5 (DW_TAG_subrange_type)
       [...]
       <40>   DW_AT_lower_bound : 5 byte block: 97 38 1c 94 4
              (DW_OP_push_object_address; DW_OP_lit8; DW_OP_minus;
               DW_OP_deref_size: 4)
       <46>   DW_AT_upper_bound : 5 byte block: 97 34 1c 94 4
              (DW_OP_push_object_address; DW_OP_lit4; DW_OP_minus;
               DW_OP_deref_size: 4)

GDB is currently printing the value of the array incorrectly:

    (gdb) p foo.three_ptr.all
    $1 = (26629472 => 1, 2,
    value.c:819: internal-error: value_contents_bits_eq: [...]

The dereferencing (".all" operator) is done by calling ada_value_ind,
which itself calls value_ind. It first produces a new value where
the bounds of the array were correctly resolved to their actual value,
but then calls readjust_indirect_value_type which replaces the resolved
type by the original type.

The problem starts when ada_value_print does not take this situation
into account, and starts using the type of the resulting value, which
has unresolved array bounds, instead of using the value's enclosing
type.

After fixing this issue, the debugger now correctly prints:

    (gdb) p foo.three_ptr.all
    $1 = (1, 2, 3)

gdb/ChangeLog:

        * ada-valprint.c (ada_value_print): Use VAL's enclosing type
        instead of VAL's type.

gdb/testsuite/ChangeLog:

        * gdb.dwarf2/dynarr-ptr.c: New file.
        * gdb.dwarf2/dynarr-ptr.exp: New file.