[PATCH] Disable specific MSVC warnings so that W4 warnings can be enabled.

[Aaron Ballman]

On Tue, Mar 24, 2015 at 3:38 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Tue, Mar 24, 2015 at 12:36 PM, Aaron Ballman <aaron at aaronballman.com>
> wrote:
>>
>> On Tue, Mar 24, 2015 at 2:42 PM, David Blaikie <dblaikie at gmail.com> wrote:
>> >
>> >
>> > On Tue, Mar 24, 2015 at 11:29 AM, Andy Kaylor <andrew.kaylor at intel.com>
>> > wrote:
>> >>
>> >> REPOSITORY
>> >>   rL LLVM
>> >>
>> >> ================
>> >> Comment at: cmake/modules/HandleLLVMOptions.cmake:286
>> >> @@ +285,3 @@
>> >> +    -wd4706 # Suppress 'assignment within conditional expression'
>> >> +    -wd4310 # Suppress 'cast truncates constant value'
>> >> +    -wd4701 # Suppress 'potentially uninitialized local variable'
>> >> ----------------
>> >> dblaikie wrote:
>> >> > You mentioned this one fired ~200 times - this might actually be
>> >> > worth
>> >> > doing a small sample check to see what it's firing on. Perhaps these
>> >> > are
>> >> > things we should fix - unless they appear in dependent expressions in
>> >> > templates, in which case they're probably false positives.
>> >> >
>> >> > The rest of these disables I'm totally fine with - if you want,
>> >> > please
>> >> > commit them separately/ahead of the rest of the review.
>> >> These look pretty harmless.  All of the ones I looked at were something
>> >> like these:
>> >>
>> >> ```
>> >> uint8_t(~0U)
>> >> (char)0xFF
>> >> (uint16_t)-1U
>> >
>> >
>> > Yeah, those all look like they do exactly what the user intended... I
>> > wonder
>> > if MSVC expects those to be written some other way? *shrug*
>>
>> MSVC is very picky about the way you write unsigned values like that.
>> ~0U is about the only way to get it to not complain (aside from
>> spelling out the full bit pattern). We do run into this fairly
>> frequently in practice.
>
>
> Sounds like it warned on "uint8_t(~0U)" too, though?

Ah, yeah, because of the cast trunctating (sorry, I thought it was
whining about signed vs unsigned for things like -1U, which it will
warn on, but that's a different warning). Sorry for the confusion!

~Aaron