Re: C++20 and gcc12/10

[Jonathan Perkin <jperkin%pkgsrc.org@localhost>]

* On 2025-04-04 at 02:17 BST, David Holland wrote:

> Is it reasonable to commit
>
>  -USE_CXX_FEATURES=      c++20
>  +# gcc10's C++20 support seems to be adequate and since an explicit
>  +# requirement of C++20 requires building gcc12 on 10.x and elsewhere,
>  +# hold off on the stricter constraint for now.
>  +#USE_CXX_FEATURES=     c++20
>  +GCC_REQD+=             10
>
> in packages where it works? It's easy enough to put back the stronger
> constraint if the build stops working.

No, this belongs in infrastructure.  A package should only have to 
declare what it needs in terms of compiler support, not have OS-specific 
hacks spread across them.  Since adding support for *_FEATURES there 
shouldn't be any GCC_REQD in packages.

> (Or would it be better to add a new CXX_FEATURE for this, like
> c++20-gcc10 or something? I am not at all clear on how any of this
> interacts with clang.)

What needs to happen is these NetBSD-specific hacks need to move to 
mk/platform/NetBSD.mk.  gcc.mk should contain what is correct for gcc, 
and then if there are hacky workarounds required to try and avoid those 
requirements to retain the ability to use the system compiler then they 
are overridden there, without affecting anyone else.

Also, if only specific parts of c++20 are required and they would be 
satisfied by GCC 10.x then they should be newly added to 
USE_CXX_FEATURES and handled appropriately.

--
Jonathan Perkin                    pkgsrc.smartos.org
Open Source Complete Cloud   www.tritondatacenter.com