Re: [PATCH] Add __attribute__((malloc) to allocator and remove unused code

[Marc Glisse <marc.glisse@inria.fr>]

On Mon, 14 May 2018, Jonathan Wakely wrote:

> As discussed at https://gcc.gnu.org/ml/libstdc++/2018-01/msg00073.html
> we can simplify the allocator function for valarray memory. I also
> noticed that the _Array(size_t) constructor is never used.
>
> 	* include/bits/valarray_array.h (__valarray_get_memory): Remove.
> 	(__valarray_get_storage): Call operator new directly. Remove ignored
> 	top-level restrict qualifier and add malloc attribute instead.

I am trying to understand the point of adding this attribute. The function 
is just

{ return static_cast<_Tp*>(operator new(__n * sizeof(_Tp))); }

The idea is that it isn't safe (? see PR 23383) to mark operator new with 
the attribute, but it is safe for this particular use?

When optimizing, I certainly hope this trivial function gets inlined, and 
then the attribute is lost (should the inliner add 'restrict' when 
inlining a function with attribute malloc?) and all that matters is 
operator new.

-- 
Marc Glisse