[libcamera-devel] [PATCH 01/17] meson: Allow partially initializing objects

[Kieran Bingham]

Hi Niklas,

On 29/05/2019 22:13, Kieran Bingham wrote:
> Hi Niklas, Jacopo,
> 
> On 27/05/2019 10:18, Jacopo Mondi wrote:
>> Hi Niklas,
>>
>> On Mon, May 27, 2019 at 02:15:27AM +0200, Niklas Söderlund wrote:
>>> There are valid use-cases where one might wish to partially initialize a
>>> structure when creating it without needing to initialize all members.
>>> This is especially common when working with V4L2.
>>>
>>> struct foo {
>>>     int bar;
>>>     int baz;
>>> };
>>>
>>> struct foo f = {
>>>     .bar = 1;
>>> };
>>>
>>> Without -Wno-missing-field-initializers fails to compile with the error,
>>
>> I asked for the same a few weeks ago, so I welcome this change
>> Acked-by: Jacopo Mondi <jacopo at jmondi.org>
> 
> I was uncertain before, but I can't deny it would be useful to simplify
> code /iff/ you know certain members do not need to be initialised.
> 
> We'll have to watch our reviews more closely on initialising structures :-)
> 
> 
> Acked-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


Errr,,, uhmmm ... sorry - Ack retracted? :-(

This breaks compilation on GCC v5 and GCC v6.

(Raspbian has GCC v6.3, and compilation on the target fails.)


To fix, I had to make the following change for this series.
Other solutions may also exist :-)

> @@ -309,15 +309,15 @@ std::vector<unsigned int> V4L2Subdevice::enumPadCodes(unsigned int pad)
>  {
>  	std::vector<unsigned int> codes;
>  	int ret;
>  
>  	for (unsigned int index = 0;; index++) {
> -		struct v4l2_subdev_mbus_code_enum mbusEnum = {
> -			.pad = pad,
> -			.index = index,
> -			.which = V4L2_SUBDEV_FORMAT_ACTIVE,
> -		};
> +		struct v4l2_subdev_mbus_code_enum mbusEnum;
> +
> +		mbusEnum.pad = pad;
> +		mbusEnum.index = index;
> +		mbusEnum.which = V4L2_SUBDEV_FORMAT_ACTIVE;
>  
>  		ret = ioctl(fd_, VIDIOC_SUBDEV_ENUM_MBUS_CODE, &mbusEnum);
>  		if (ret)
>  			break;
>  
> @@ -340,16 +340,16 @@ std::vector<SizeRange> V4L2Subdevice::enumPadSizes(unsigned int pad,
>  {
>  	std::vector<SizeRange> sizes;
>  	int ret;
>  
>  	for (unsigned int index = 0;; index++) {
> -		struct v4l2_subdev_frame_size_enum sizeEnum = {
> -			.index = index,
> -			.pad = pad,
> -			.code = code,
> -			.which = V4L2_SUBDEV_FORMAT_ACTIVE,
> -		};
> +		struct v4l2_subdev_frame_size_enum sizeEnum;
> +
> +		sizeEnum.index = index;
> +		sizeEnum.pad = pad;
> +		sizeEnum.code = code;
> +		sizeEnum.which = V4L2_SUBDEV_FORMAT_ACTIVE;
>  
>  		ret = ioctl(fd_, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, &sizeEnum);
>  		if (ret)
>  			break;






> 
>>>
>>>     error: missing initializer for member ‘foo::baz’ [-Werror=missing-field-initializers]
>>>
>>> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
>>> ---
>>>  meson.build | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/meson.build b/meson.build
>>> index 4d3e99d3e58f71d5..90ad58328f9a2bd5 100644
>>> --- a/meson.build
>>> +++ b/meson.build
>>> @@ -22,6 +22,7 @@ endif
>>>
>>>  common_arguments = [
>>>      '-Wno-unused-parameter',
>>> +    '-Wno-missing-field-initializers',
>>>      '-include', 'config.h',
>>>  ]
>>>
>>> --
>>> 2.21.0
>>>
>>> _______________________________________________
>>> libcamera-devel mailing list
>>> libcamera-devel at lists.libcamera.org
>>> https://lists.libcamera.org/listinfo/libcamera-devel
>>>
>>> _______________________________________________
>>> libcamera-devel mailing list
>>> libcamera-devel at lists.libcamera.org
>>> https://lists.libcamera.org/listinfo/libcamera-devel
> 

-- 
Regards
--
Kieran