Re: [PATCH] vsprintf.c: Reduce sizeof struct printf_spec from 24 to8 bytes

[Linus Torvalds]

On Sat, 6 Mar 2010, Linus Torvalds wrote:

> the 'pointer()' function has a 200+ byte stack footprint on x86-64. And 
> vsnprintf itself is about 100+ bytes. So that stack depth is way bigger 
> than I would have expected.
> 
> I'm not sure _why_ that stack footprint for 'pointer()' is so big, but I 
> bet it's due to some simple inlining, and gcc (once more) sucking at it 
> and not being able to combine stack frames. It's a damn shame.

Yeah, a few noinline's gets 'pointer()' to just save registers on the 
stack, no need for any extra buffers (which then is ok for your recursion 
case - the other subfunctions it can call have their own buffers, of 
course, but they won't be in the recursive call-path except at the leaf.

vsnprintf() itself seems less obviously fixable. I'm not sure wht gcc 
decides it needs 88 bytes of temp-space there.

		Linus
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