[Bug fortran/31282] [gdb/fortran] logical type doesn't match documentation of TYPE_CODE_BOOL

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31282

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom Tromey from comment #1)
> It's also worth considering how hardbool should work.

Ah, interesting, thanks.  I found some explanation here (
https://gcc.gnu.org/onlinedocs/gnat_rm/Hardened-Booleans.html ).

So let's try with this program:
...
with Text_IO; use Text_IO;

procedure hello is
   type HBool is new Boolean;
   for HBool use (0, 1);
   for HBool'Size use 8;
   A : HBool := True;
begin
   Put_Line("Hello world!");
end hello;
...

This dwarf is generated, it's a subrange_type:
...
 <2><168e>: Abbrev Number: 3 (DW_TAG_subrange_type)
    <168f>   DW_AT_lower_bound : 0
    <1690>   DW_AT_upper_bound : 1
    <1691>   DW_AT_name        : hello__hbool
    <1695>   DW_AT_type        : <0x16a7>
 <1><16a7>: Abbrev Number: 5 (DW_TAG_base_type)
    <16a8>   DW_AT_byte_size   : 1
    <16a9>   DW_AT_encoding    : 2      (boolean)
    <16aa>   DW_AT_name        : hello__hboolB
    <16ae>   DW_AT_artificial  : 1
...

Now let's try this change:
...
-   for HBool use (0, 1);
+   for HBool use (0, 2);
...

Also a subrange_type, but with a different basis type.
...
 <2><168a>: Abbrev Number: 3 (DW_TAG_enumeration_type)
    <168b>   DW_AT_name        : hello__hboolB
    <168f>   DW_AT_encoding    : 7      (unsigned)
    <1690>   DW_AT_byte_size   : 1
    <1694>   DW_AT_artificial  : 1
 <3><1698>: Abbrev Number: 4 (DW_TAG_enumerator)
    <1699>   DW_AT_name        : false
    <169d>   DW_AT_const_value : 0
 <3><169e>: Abbrev Number: 4 (DW_TAG_enumerator)
    <169f>   DW_AT_name        : true
    <16a3>   DW_AT_const_value : 2
 <2><16a5>: Abbrev Number: 5 (DW_TAG_subrange_type)
    <16a6>   DW_AT_lower_bound : 0
    <16a7>   DW_AT_upper_bound : 2
    <16a8>   DW_AT_name        : hello__hbool
    <16ac>   DW_AT_type        : <0x168a>
...

Likewise for:
...
-   for HBool use (0, 1);
+   for HBool use (1, 2);
...
which sort of suggests that DW_ATE_boolean means 0/1, but that is contradicted
by the use of DW_ATE_boolean in ifort.

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