Hi Stuart,

there has been a new release and he has bumped the fmt library ... and
issued a new release  there just now

:)

Happy to help with the update  of ports

Thanks
Tom Smyth

On Sat, 30 May 2026 at 15:36, Stuart Henderson <stu@spacehopper.org> wrote:

> On 2026/05/21 10:47, Tom Smyth wrote:
> > I was talking to Pavel  (from fastnetmon) and  he responded posively
> asked the following
> > "Can you provide summary what's required from our side? "
>
> so, now that we have switched the system compiler in -current to
> LLVM 22, unfortunately fastnetmon no longer builds.
>
> it gets this far before failing:
>
> fmt/format-inl.h:2515:30: error: call to consteval function
> 'fmt::basic_format_string<char, unsigned int
> &>::basic_format_string<FMT_COMPILE_STRING, 0>' is not a constant expression
>  2515 |         out = format_to(out, FMT_STRING("{:x}"), value);
> ...
> fmt/format-inl.h:2519:28: error: call to consteval function
> 'fmt::basic_format_string<char, unsigned int
> &>::basic_format_string<FMT_COMPILE_STRING, 0>' is not a constant expression
>  2519 |       out = format_to(out, FMT_STRING("{:08x}"), value);
>
> it looks like this maybe due to the workaround that fmt are using
> for an old gcc bug, but in any event, checking the version of fmt ...
>
> | fmt/core.h
> | 18:// The fmt library version in the form major * 10000 + minor * 100 +
> patch.
> | 19:#define FMT_VERSION 80000
>
> this is rather old, so it would probably be best if fastnetmon updates
> to a less ancient version (this is likely to require some code changes
> in fastnetmon to make it work but shouldn't be too hard). I believe
> there may be some other issues on newer LLVM, at least when fmt is
> compiled in C++20 mode (as fastnetmon is requesting).
>
> if Pavel is able to update fmt (or otherwise workaround), I'm happy
> to test again and see if we hit any other issues.
>
>
> there are also non-fatal warnings around nlohmann-json; again,
> fastnetmon has an old version and could do with updating. in this case
> I think it should just be possible to update to a newer version from
> https://github.com/nlohmann/json/tree/develop/single_include/nlohmann
> without other changes.
>
>

-- 
Kindest regards,
Tom Smyth.