Template aliases and attributes
Alexander Monakov
amonakov@ispras.ru
Fri Nov 29 15:44:00 GMT 2019
On Fri, 29 Nov 2019, Martin Reinecke wrote:
> Hi,
>
> g++ is unhappy about the statement:
>
> template<typename T, int len> using vtype = T __attribute__
> ((vector_size (len*sizeof(T))));
>
> and reports:
>
> vectest.cc:1:91: warning: ignoring attributes applied to dependent type
> âTâ without an associated declaration [-Wattributes]
> 1 | using vtype = T __attribute__ ((vector_size (len*sizeof(T))));
> | ^
>
> clang++ on the other hand seems to be OK with this.
>
> Is there some subtlety I'm missing?
> If so, is there analternative way to express what I have in mind?
gcc expects the attribute on the type being declared, not the base type,
so you need to place the attribute on vtype:
template<typename T, int len>
using vtype __attribute__ ((vector_size (len*sizeof(T)))) = T;
This matches how [[attributes]] are meant to be placed in C++11 alias templates.
Alexander
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