[cfe-dev] clang::Qualifiers::TQ flags are not in sync with DeclSpec::TQ flags

[Vladimir Voskresensky via cfe-dev]

On 10.08.2017 18:19, John McCall wrote:
>> On Aug 10, 2017, at 7:56 AM, Vladimir Voskresensky <vladimir.voskresensky at oracle.com> wrote:
>> On 10.08.2017 02:31, John McCall wrote:
>>>> On Aug 9, 2017, at 4:51 PM, Vladimir Voskresensky via cfe-dev <cfe-dev at lists.llvm.org> wrote:
>>>> Ping,
>>>>
>>>> Could someone comment, please, if clang::Qualifiers::TQ intentionally reduces number of flags from 5 to 3?
>>> It is not intentional, no.  We do not represent _Atomic as an ordinary qualifier in the AST, so I think this might accidentally be okay there.  Offhand, I don't think we want to support either of those qualifiers as an array index type qualifier unless the C spec absolutely demands it.
>> Ok. Thanks for the information. I was mislead by
>> comment in clang::Qualifiers::TQ
>> // NOTE: These flags must be kept in sync with DeclSpec::TQ.
>> and the test where 5 bits value was written into 3 bits field.
>>
>> Would be great if "note" can be clarified as well.
> If something is just blindly trying to propagate the DeclSpec::TQ around, that seems problematic.
If only 3 flags are really wanted here, then probably this line

ArrayTypeBits.IndexTypeQuals = tq;

should use cleaning mask:
ArrayTypeBits.IndexTypeQuals = tq & Qualifiers::CVRMask;

Vladimir.
>
> I think the comment is more about the flag values than the full set of flags, but yes, that should be clarified.
>
> John.
>
>> Thanks
>> Vladimir.
>>
>>> John.
>>>
>>>> Thanks,
>>>> Vladimir.
>>>>
>>>> On 07.08.2017 16:06, Vladimir Voskresensky via cfe-dev wrote:
>>>>> Hello,
>>>>>
>>>>> clang::Qualifiers::TQ has 3 flags and CVRMask mask. Also it has the note:
>>>>> // NOTE: These flags must be kept in sync with DeclSpec::TQ.
>>>>>
>>>>> But
>>>>> DeclSpec::TQ has 5 flags (so  TQ_unaligned = 8, TQ_atomic = 16 are missed in clang::Qualifiers::TQ)
>>>>>
>>>>> This inconsistency can be found by debugging test llvm/tools/clang/test/Sema/MicrosoftExtensions.c on the last declaration:
>>>>> void test_unaligned2(int x[__unaligned 4]) {}
>>>>>
>>>>> Array type is created incorrectly here, because '__unaligned' is lost in the ArrayType constructor at line:
>>>>> ArrayTypeBits.IndexTypeQuals = tq;
>>>>> tq has value 8 (TQ_unaligned) while IndexTypeQuals is declared to use ":3" bits only, so IndexTypeQuals is zero after assign.
>>>>>
>>>>> Usually TQ fields are 5 bits (see i.e. DeclSpec::TypeQualifiers), so
>>>>> declaration Type::ArrayTypeBitfields::IndexTypeQuals must be fixed as well
>>>>>
>>>>> Hope it helps,
>>>>> Vladimir.
>>>>>
>>>>>
>>>>>
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