Re: [PATCH 2/2] use __builtin_add_overflow() in st_add() with Clang

[Jeff King <peff@peff.net>]

On Fri, May 15, 2026 at 04:36:15PM +0200, René Scharfe wrote:

> > I guess the ideal primitive is probably a wrapper with the same
> > interface as __builtin_add_overflow(), which could then be used
> > everywhere that unsigned_add_overflows() with some minor conversion.
> 
> Junio said the same. :)
> > But it gets awkward to do as a macro, and using an inline function runs
> > into type questions.
> Indeed.  If it was easy then this wouldn't exist as a builtin.  We
> can approximate it somewhat, but will it be robust enough?

I always thought it was a builtin because the most efficient way
involves checking the carry flag, which can't be accessed from C.

But yeah, the type issues are real, too. ;)

I think we should take what you posted for now, and we can iterate on a
more general add-and-check interface later (or never if it's too
tricky).

-Peff