Re: [PATCH v1 1/2] overflow: Allow to sum a few arguments at once

[Johannes Berg]

On Wed, 2026-06-17 at 13:12 +0200, Andy Shevchenko wrote:
> Convert size_add() to take variadic argument, so we can simplify users
> with using a macro only once.

> +#define __size_add3(addend1, addend2, addend3, addend4, ...)			\
> +	__size_add(__size_add2(addend1,  addend2, addend3), addend4)
> +#define __size_add4(addend1, addend2, addend3, addend4, addend5, ...)		\
> +	__size_add(__size_add3(addend1,  addend2, addend3, addend4), addend5)

I guess it's not going to really matter, but it would generate fewer
calls to have something more like

#define __size_add3(a1, a2, a3, a4) \
	size_add(size_add(a1, a2), size_add(a3, a4))
#define __size_add4(a1, a2, a3, a4, a5) \
	size_add(size_add(a1, a2), size_add(a3, a4, a5))

as a binary tree, rather than only cutting one off every time. Not sure
that results in hugely different code though - maybe fewer overflow
checks?

Although your version make it really completely equivalent to the
nl80211.c code, clearly it doesn't matter if all the values are "good",
and I believe the overflow behaviour means it doesn't matter for the
overflow case either?

johannes