Re: What's the newest C++ standard that we can target?

On 8 Jan 2025, at 18:46, Alan Somers <asomers@freebsd.org> wrote:
> 
> On Wed, Jan 8, 2025 at 10:44 AM Dimitry Andric <dim@freebsd.org> wrote:
>> 
>> On 8 Jan 2025, at 18:31, Alan Somers <asomers@freebsd.org> wrote:
>>> 
>>> What is the newest C++ standard that we can target in src, and be
>>> confident that it will compile on all targets?  Can we use C++20?
>> 
>> C++17 is probably the safest one, as C++20 support in libc++ 19 is
>> mostly done, but not entirely complete:
>> 
>> https://libcxx.llvm.org/Status/Cxx20.html
>> 
>> As long as you avoid modules, and the more exotic parts, you should be
>> fine. One glaring remaining issue is that std::jthread support is still
>> gated under -fexperimental-library, at least until libc++ 20 comes out.
>> 
>> That said, older existing releases don't have libc++ 19 yet, and they
>> are missing a few headers too. So it depends on whether you want to
>> target -CURRENT only?
>> 
>> -Dimitry
> 
> I guess I should've mentioned that I would like to MFC to stable/14,
> too.

llvm-19 was already merged to stable/14 and stable/13, so that should be
no problem.


>  I certainly intend to avoid exotic parts.  Is there any better
> way to ensure that may code will build other than "make universe"?

If you are on a recent -CURRENT system, you should be able to build
the program standalone. If you add it to the base system, you should
only have to do special handling if you want to make it part of the
bootstrap tools or cross-tools phase.

-Dimitry