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

[Richard Smith via llvm-dev]

On 10 April 2017 at 07:33, David Blaikie via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> For the case of a redundant or unneeded std::move, I think Clang already
> has something like that...
>
> Ah, it doesn't quite catch that particular case.
>
> Richard - would it be reasonable to extend the pessimizing move warning
> (well, I guess not - maybe as a separate warning) for cases like this:
>
> void f(const foo&);
> void g(foo x) {
>   f(std::move(x));
> }
>
> Or maybe there's already a clang-tidy check for this sort of redundant
> move?
>

There's already a clang warning for redundant moves (-Wredundant-move). It
doesn't yet catch the above pattern, but it should...


> 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...
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>
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