On Fri, 17 Dec 2021, Abramo Bagnara wrote:

In the specific of your PR: have you considered that if, instead to keep
increasing buf, you increase a buffer offset you would avoid to do ugly tricks
and NULL subtraction?

Well... I took this as a challenge and attempted it.

And it didn't work satisfactorily.

The problem is that the buf pointer accomplishes two roles: it serves as
a buffer offset as well as a memory boundary indicator used for argument
alignment. Going with a buffer base and an explicit offset doesn't allow
for proper alignment without also taking the buffer base into account.
If the buffer base is NULL then you need yet another variable to hold
the misalignment. This complexifies the code, increases register
pressure, makes resulting binary bigger, and doesn't look any better in
the end.

So my efforts resulted in the following PR instead which I hope would be
an acceptable middle ground.

https://github.com/zephyrproject-rtos/zephyr/pull/41321


Nicolas