[llvm-dev] Spurious cast warning for C++?

[mats petersson via llvm-dev]

What does "have no effect" mean in this case? In my mind, there are many
casts that have no effect - other than allowing the code to compile, which
is quite an important effect in itself (e.g. casting a 32-bit unsigned to a
pointer on your typical 32-bit system).

Are you seeking to warn for:

   int a;
   int b;

   a = (int) b;

and similar things?

--
Mats

On 9 April 2017 at 20:35, Craig Topper via llvm-dev <llvm-dev at lists.llvm.org
> wrote:

> This is question is probably better on the clang  cfe-dev list.
>
> On Sun, Apr 9, 2017 at 12:01 PM Brennan Vincent via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> How difficult would it be to add a warning to Clang when the programmer
>> performs a cast that provably has no effect?
>>
>> A particular case I have in mind is someone getting confused and calling
>> std::move on an argument to a copy-constructor for a class that doesn't
>> implement move semantics.
>>
>> I would be grateful if someone either (1) told me why this is
>> difficult/impossible, or (2) gave me some pointers to where I could
>> start trying to implement it...
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> --
> ~Craig
>
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