Re: [PATCH] 9p: move limits.h include from 9p.c to 9p.h

[Peter Maydell]

On Wed, 30 Mar 2022 at 22:55, Will Cohen <wwcohen@gmail.com> wrote:
>
> On Wed, Mar 30, 2022 at 5:31 PM Peter Maydell <peter.maydell@linaro.org> 
> wrote:
>> Is it possible to do this with a meson.build check for whatever
>> host property we're relying on here rather than with a
>> "which OS is this?" ifdef ?
>
>
> To confirm -- the game plan in this case would be to do a check for something 
> along the lines of
> config_host_data.set('CONFIG_XATTR_SIZE_MAX', 
> cc.has_header_symbol('linux/limits.h', 'XATTR_SIZE_MAX'))
> and using that in the corresponding ifs, right?
>
> That makes sense -- if there's no objections, I'll go this route for v2, 
> which I can submit tomorrow.

Yeah, something like that.

Looking a bit closer at the code it looks like the handling of
XATTR_SIZE_MAX is kind of odd: on Linux we use this kernel-provided
value, whatever it is, on macos we use a hardcoded 64K, and on
any other host we fail to compile. The comment claims we only
need to impose a limit to avoid doing an overly large malloc,
but if that's the case this shouldn't be OS-specific. I suspect
the problem here is we're trying to impose a non-existent fixed
maximum size for something where the API on the host just doesn't
guarantee one.

But that would be a 7.1 thing to look at improving.

-- PMM