Re: [PATCH v3 1/1] include: Don't include qemu/osdep.h

[Peter Maydell]

On Thu, 12 Jan 2023 at 16:08, Daniel P. Berrangé <berrange@redhat.com> wrote:
> I think the challenge is that osdep.h is too big as it exists
> today. The stuff the needs to come before system headers is
> actually little more than config-host.h and a few #defines
> most of which are specific to windows. If those critical
> #defines went into config-host.h, then we could have a rule
> 'config-host.h' must be included in all .c files as the first
> thing.

This doesn't seem much different to the rules we have today,
except you've renamed osdep.h to config-host.h...

> All the header files could just reference the specific
> system headers they care about instead of making everything
> from osdep.h visible in their namespace.  Still this would be
> quite a lot of work to adapt to at this point.

It certainly does have more in it than strictly necessary,
though we have thinned it out quite a bit from when we
first put in the convention. A lot of the functions at
the tail end of the file could be moved out into their
own headers, for instance -- patches welcome ;-)

> All the header files could just reference the specific
> system headers they care about instead of making everything
> from osdep.h visible in their namespace.

There are some complicated things in there, not always
limited to Windows. Also where there is some header
that needs a platform-specific workaround I prefer that
that header is pulled in by osdep.h. This avoids the
failure mode of "developer working on Linux directly
includes some-system-header.h; works fine on their machine,
but doesn't work on oddball-platform where the header
needs a workaround". (For instance, handling "sys/mman.h
on this system doesn't define MAP_ANONYMOUS", or the
backcompat stuff in glib-compat.h.)

thanks
-- PMM