[libcamera-devel] [PATCH v3] cam: file_sink: Fixes following errors with gcc-13

[Khem Raj]

On Tue, Mar 28, 2023 at 10:13 AM Kieran Bingham
<kieran.bingham at ideasonboard.com> wrote:
>
> Hi Eric,
>
> Quoting Eric Curtin (2023-02-20 04:55:24)
> > ../git/src/cam/file_sink.cpp:92:45: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
> >    92 |                 const FrameMetadata::Plane &meta = buffer->metadata().planes()[i];
> >       |                                             ^~~~
> > ../git/src/cam/file_sink.cpp:92:81: note: the temporary was destroyed at the end of the full expression '(& buffer->libcamera::FrameBuffer::metadata())->libcamera::FrameMetadata::planes().libcamera::Span<const libcamera::FrameMetadata::Plane>::operator[](i)'
> >    92 |                 const FrameMetadata::Plane &meta = buffer->metadata().planes()[i];
> >       |                                                                                 ^
> > cc1plus: all warnings being treated as errors
> >
> > Co-developed-by: Khem Raj <raj.khem at gmail.com>
> > Signed-off-by: Eric Curtin <ecurtin at redhat.com>
>
> I'm still hoping that holding off a little on this will ensure it's
> fixed in the compiler before GCC-13 is released - but I think I can also
> already add:
>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>
> And given a fix was added to gcc-13, but it didn't fix /this/ we may be
> getting to the point that we'll simply have to merge this. I guess it
> depends on when gcc-13 is actually released?

In a months time. It perhaps is not going to be fixed by atleast the
first 13.x release. Maybe subsequent point releases
might have it

>
> --
> Kieran
>
>
> > ---
> > Changes in v3:
> >
> > - Added comment explaining change made because of false negative in gcc
> >
> > Changes in v2:
> >
> > - Added const
> > - Made patch mergeable by accounting for new directory structure
> > ---
> >  src/apps/cam/file_sink.cpp | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/apps/cam/file_sink.cpp b/src/apps/cam/file_sink.cpp
> > index b32aad24..01846cdb 100644
> > --- a/src/apps/cam/file_sink.cpp
> > +++ b/src/apps/cam/file_sink.cpp
> > @@ -114,13 +114,17 @@ void FileSink::writeBuffer(const Stream *stream, FrameBuffer *buffer,
> >         }
> >
> >         for (unsigned int i = 0; i < buffer->planes().size(); ++i) {
> > -               const FrameMetadata::Plane &meta = buffer->metadata().planes()[i];
> > -
> > +               /*
> > +                * formerly "const FrameMetadata::Plane &"
> > +                * causing false negative (gcc 13):
> > +                * "possibly dangling reference to a temporary"
> > +                */
> > +               const unsigned int bytesused = buffer->metadata().planes()[i].bytesused;
> >                 Span<uint8_t> data = image->data(i);
> > -               unsigned int length = std::min<unsigned int>(meta.bytesused, data.size());
> > +               const unsigned int length = std::min<unsigned int>(bytesused, data.size());
> >
> > -               if (meta.bytesused > data.size())
> > -                       std::cerr << "payload size " << meta.bytesused
> > +               if (bytesused > data.size())
> > +                       std::cerr << "payload size " << bytesused
> >                                   << " larger than plane size " << data.size()
> >                                   << std::endl;
> >
> > --
> > 2.39.1
> >