[PATCH] D17043: Check that the result of a library call w/o side effects is used

[Richard Smith via cfe-commits]

On Wed, Feb 10, 2016 at 5:05 PM, Joerg Sonnenberger via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> On Wed, Feb 10, 2016 at 04:21:02PM +0000, Alexander Kornienko via cfe-commits wrote:
>> alexfh added a comment.
>>
>> Thank you for working on this check!
>>
>> I'd like to note that there is a library-side way to mitigate this
>> issue using the `[[clang::warn_unused_result]]` attribute on
>> `vector::empty()` and similar methods:
>
> I'm not a big fan of this. Those calls are by the very definition
> harmless, so they aggrevate the existing problem of stupid annotation.
> The original intention of this attribute was to flag cases of side
> effects where ignoring the the result is a definite bug. Consider
> calling malloc or realloc and throwing away the result -- that never
> makes sense. Then GNU came along and starting to annotate various libc
> functions including most of the stdio family. Guess what, standard
> streams have a (sticky) error flag, exactly so that you don't have check
> every single call. Congratulation, people are just starting to ignore
> the warnings now. Fast forward and we have this suggestion...

I'm not sure what point you're making here. A call to vector::empty()
that discards the result is always a bug; usually, the intent was to
call vector::clear() instead, and the problem isn't just pointless
code.