[libcamera-devel] [PATCH] android: Rework request completion notification

[Niklas Söderlund]

Hi Jacopo,

On 2021-05-06 10:53:02 +0200, Jacopo Mondi wrote:

<snip>

> > >
> > > -	resultMetadata = getResultMetadata(descriptor);
> > > +	/*
> > > +	 * Generate the metadata associated with the captured buffers.
> > > +	 *
> > > +	 * Notify if the metadata generation has failed, but continue processing
> > > +	 * buffers and return an empty metadata pack.
> > > +	 */
> > > +	std::unique_ptr<CameraMetadata> resultMetadata = getResultMetadata(descriptor);
> > > +	if (!resultMetadata)
> > > +		notifyError(descriptor.frameNumber_, descriptor.buffers_[0].stream,
> > > +			    CAMERA3_MSG_ERROR_RESULT);
> > > +	captureResult.result = resultMetadata->get();
> >
> > Hum if !resultMetadata will not resultMetadata->get() give us a nullptr
> > exception here?
> >
> 
> According to the std::unique_ptr<>::get() documentation:
> 
> "Returns a pointer to the managed object or nullptr if no object is owned."
> 
> as getResultMetadata() returns nullptr on error, and the function
> signature is
>         std::unique_ptr<CameraMetadata> CameraDevice::getResultMetadata()
> 
> my understanding is that the returned unique_ptr<> will own no object,
> hence get() should return nullptr. Or have I missed something about
> the "no object is owned" vs "a unique_ptr<> that owns nullptr" ?

I share your understanding of std::unique_ptr<>::get() but that would be 

    resultMetadata.get()

and not

    resultMetadata->get()

The later calls CameraMetadata::get() which returns camera_metadata_t * 
which is the correct datatype for the captureResult.result right? So I 
think the code calls the correct get(), only the manual protection for 
the nullptr is missing.

-- 
Regards,
Niklas Söderlund