Re: [Qemu-devel] [PATCH for-4.0 v7 01/27] qapi: make sure osdep.h is included in type headers

[Marc-André Lureau]

Hi

On Mon, Dec 10, 2018 at 1:52 PM Markus Armbruster <address@hidden> wrote:
>
> Marc-André Lureau <address@hidden> writes:
>
> > Now that the schema can be configured, it is crucial that all types
> > are configured the same. Make sure config-host.h is included, by
> > checking osdep.h inclusion. The build-sys tracks the dependency and
> > rebuilds the types if the configuration changed.
> >
> > Signed-off-by: Marc-André Lureau <address@hidden>
> > ---
> >  scripts/qapi/types.py | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
> > index fd7808103c..3bb9cb6d47 100644
> > --- a/scripts/qapi/types.py
> > +++ b/scripts/qapi/types.py
> > @@ -201,6 +201,9 @@ class 
> > QAPISchemaGenTypeVisitor(QAPISchemaModularCVisitor):
> >  ''',
> >                                        types=types, visit=visit))
> >          self._genh.preamble_add(mcgen('''
> > +#ifndef QEMU_OSDEP_H
> > +#error Please include osdep.h first!
> > +#endif
> >  #include "qapi/qapi-builtin-types.h"
> >  '''))
>
> I understand why you propose this patch.  The QAPI-generated headers use
> #ifdef CONFIG_FOO.  The configuration header "qemu/osdep.h" must be
> consistently included before the generated headers, or else you end up
> with nasty bugs, such as the same enum having different values in
> different .o, or the same struct having a different layout.
>
> But this applies to *all* headers that use #ifdef.  Why check it here,
> but not there?  What makes the QAPI-generated headers special?
>

It's the discussion about #if in headers (and enums in particular)
that started this. We want to make sure all compilation units share
the same data structure/ABI. I proposed to include osdep.h in qapi
headers, but that was rejected.
The warning is a different approach. I agree it could apply to all
headers. Do you think I should update all headers as well?


-- 
Marc-André Lureau