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

[John McCall via cfe-dev]

> 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.

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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