[PATCH v1] libcamera: controls: Check size of enum

[Kieran Bingham]

Quoting Kieran Bingham (2025-03-17 17:56:43)
> Quoting Barnabás Pőcze (2025-03-10 17:02:54)
> > Only enums whose sizes match that of `int32_t` can be directly
> > supported. Otherwise the expected size and the real size would
> > disagree, leading to an assertion failure in `ControlValue::set()`.
> > 
> > Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
> 
> Has this happened? I assume if we try to make a control from an enum
> where we override the type it would now produce a compile failure (which
> I'm fine with for now).
> 
> I assume we could make similar mappings of other enum sizes if we needed
> to at that point, but I don't see that as a requirement at the moment.
> 
> This looks positively defensive so:
> 
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> We're in a public header, but I don't think this is an API breaking
> change at all is it ? If this changed anything we'd see a compile
> failure already...
> 

gitlab.freedesktop.org is starting to come back online \o/

but alas CI picked something up on this patch...

https://gitlab.freedesktop.org/camera/libcamera/-/jobs/73022971

Could you check please? (it could be false positive still or something
with the CI)

--
Kieran

> 
> > ---
> >  include/libcamera/controls.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> > index 7c7828ae5..4bfe9615c 100644
> > --- a/include/libcamera/controls.h
> > +++ b/include/libcamera/controls.h
> > @@ -125,7 +125,7 @@ struct control_type<Span<T, N>> : public control_type<std::remove_cv_t<T>> {
> >  };
> >  
> >  template<typename T>
> > -struct control_type<T, std::enable_if_t<std::is_enum_v<T>>> : public control_type<int32_t> {
> > +struct control_type<T, std::enable_if_t<std::is_enum_v<T> && sizeof(T) == sizeof(int32_t)>> : public control_type<int32_t> {
> >  };
> >  
> >  } /* namespace details */
> > -- 
> > 2.48.1
> >