[Mesa-dev] [PATCH 04/24] i965: Make 'dw1' and 'bits' unnamed structures in brw_reg.

[Francisco Jerez]

Matt Turner <mattst88 at gmail.com> writes:

> On Tue, Nov 3, 2015 at 5:48 AM, Francisco Jerez <currojerez at riseup.net> wrote:
>> Matt Turner <mattst88 at gmail.com> writes:
>>
>>> Generated by
>>>
>>>    sed -i -e 's/\.bits\././g' *.c *.h *.cpp
>>>    sed -i -e 's/dw1\.//g' *.c *.h *.cpp
>>>
>>> and then reverting changes to comments in gen7_blorp.cpp and
>>> brw_fs_generator.cpp.
>>>
>>> There wasn't any utility offered by forcing the programmer to list these
>>> to access their fields. Removing them will reduce churn in future
>>> commits.
>>>
>>> This is C11 (and gcc has apparently supported it for sometime
>>> "compatibility with other compilers")
>>>
>>> See https://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html
>>
>> This is also used from C++ source where anonymous structs are not part
>> of any released standard.
>
> That is true. I have built this series with both clang-3.6 and
> gcc-4.4.7. I don't think it's a problem.
>
>> I guess in C++ it would be preferable to
>> define accessor methods instead of relying on a language extension --
>> That would also allow you to introduce checks making sure that the
>> register is of the correct type in order to catch cases in which the
>> wrong field of the union is accessed easily.
>
> Maybe. Since I was changing so much code in this series, I wouldn't
> want to do that here.

Yeah, I agree that there's no need to make that change as part of this
series.  However if we agree that accessors would be a better approach
this patch is unnecessary, since we will get a similar kind of syntactic
sugar without relying on unnamed structures.

> Also, having commits that use the brw_reg fields separately from any
> accessors seems beneficial.
>
> We could also simply mark fields private with using declarations. That
> would get almost all of any potential benefit (of which I'm not sure
> how much there is, really).

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