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

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jan 12, 2023 at 04:20:36PM +0000, Peter Maydell wrote:
> 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...

If the QEMU header files all contain #includes for the
system headers they rely on, then when tools are validating
code in the header, they can stand a better chance of being
able to resolve all the types. Though it'll still fail if
some of the system header pieces only get exposed as a result
of config-host.h macros, but that's relatively few, compared
to today where amost nothing resolves if yuo validate the
headers files in isolation.


> > 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.)

Yeah, its not entirely straightforward, though our CI will catch
that on our most important target platforms.

With regards,
Daniel
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