[PATCH v2 6/6] libcamera: shared_mem_object: Remove is_standard_layout restriction

[Kieran Bingham]

Quoting Laurent Pinchart (2024-05-09 12:16:15)
> On Thu, May 09, 2024 at 11:49:41AM +0200, Jacopo Mondi wrote:
> > On Wed, May 08, 2024 at 09:04:01AM GMT, Naushir Patuck wrote:
> > > The shared_mem_object may be used to construct complex classes, so
> > > remove the standard layout type restriction.
> > >
> > > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > 
> > This looks fine to me, but maybe better check on why this was
> > introduced in first place.
> 
> It was added there because sharing objects containing pointers between
> different processes isn't safe. Naush, what object do you need to store
> in shared memory that has a non-standard layout, but is still safe to
> share ?

Oh, interesting point. I wonder if that's why we've seen people get
segfaults if the RPi IPA runs in isolation (as then these buffers are
shared, and could potentially contain invalid pointers?)

--
Kieran


> 
> > Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > 
> > > ---
> > >  include/libcamera/internal/shared_mem_object.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/include/libcamera/internal/shared_mem_object.h b/include/libcamera/internal/shared_mem_object.h
> > > index 9b1d939302a8..c9c0482062bd 100644
> > > --- a/include/libcamera/internal/shared_mem_object.h
> > > +++ b/include/libcamera/internal/shared_mem_object.h
> > > @@ -56,7 +56,7 @@ private:
> > >     Span<uint8_t> mem_;
> > >  };
> > >
> > > -template<class T, typename = std::enable_if_t<std::is_standard_layout<T>::value>>
> > > +template<class T>
> > >  class SharedMemObject : public SharedMem
> > >  {
> > >  public:
> 
> -- 
> Regards,
> 
> Laurent Pinchart