[libcamera-devel] [PATCH] libcamera: v4l2_device: Fix variable-sized object initialization

Jacopo Mondi jacopo at jmondi.org
Fri Jun 28 08:07:48 CEST 2019


Hi Niklas,
   sorry, I didn't test on clang. It should become a standard practice
since it's the default compiler used for building, ie, Cros..

On Wed, Jun 26, 2019 at 07:35:43PM +0200, Nklas Söderlund wrote:
> Compiling with clang renders errors as a variable-sized arrays are not
> allowed to be initialized, solve this by using memset() instead.
>
>     ../../src/libcamera/v4l2_device.cpp:155:37: error: variable-sized object may not be initialized
>         const V4L2ControlInfo *controlInfo[count] = {};
>                                            ^~~~~
>     ../../src/libcamera/v4l2_device.cpp:156:36: error: variable-sized object may not be initialized
> 	    struct v4l2_ext_control v4l2Ctrls[count] = {};
> 					      ^~~~~
>     ../../src/libcamera/v4l2_device.cpp:227:37: error: variable-sized object may not be initialized
> 	    const V4L2ControlInfo *controlInfo[count] = {};
> 					       ^~~~~
>     ../../src/libcamera/v4l2_device.cpp:228:36: error: variable-sized object may not be initialized
> 	    struct v4l2_ext_control v4l2Ctrls[count] = {};
> 					      ^~~~~
> Fixes: eb068f4e67eedacd ("libcamera: v4l2_device: Implement get and set controls")
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  src/libcamera/v4l2_device.cpp | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index 84758a811c271976..d730df78e1ab2478 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -152,8 +152,11 @@ int V4L2Device::getControls(V4L2ControlList *ctrls)
>  	if (count == 0)
>  		return 0;
>
> -	const V4L2ControlInfo *controlInfo[count] = {};
> -	struct v4l2_ext_control v4l2Ctrls[count] = {};
> +	const V4L2ControlInfo *controlInfo[count];

No need to zero this one.

> +	struct v4l2_ext_control v4l2Ctrls[count];

We can initialize each entry as we walk them maybe?

--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -152,8 +152,8 @@ int V4L2Device::getControls(V4L2ControlList *ctrls)
        if (count == 0)
                return 0;

-       const V4L2ControlInfo *controlInfo[count] = {};
-       struct v4l2_ext_control v4l2Ctrls[count] = {};
+       const V4L2ControlInfo *controlInfo[count];
+       struct v4l2_ext_control v4l2Ctrls[count];
        for (unsigned int i = 0; i < count; ++i) {
                const V4L2Control *ctrl = ctrls->getByIndex(i);
                const V4L2ControlInfo *info = getControlInfo(ctrl->id());
@@ -164,6 +164,7 @@ int V4L2Device::getControls(V4L2ControlList *ctrls)
                }

                controlInfo[i] = info;
+               v4l2Ctrls[i] = {};
                v4l2Ctrls[i].id = info->id();
        }
With the same to be done for setControl()?

What do you think?

> +	memset(controlInfo, 0, count * sizeof(controlInfo[0]));
> +	memset(v4l2Ctrls, 0, count * sizeof(v4l2Ctrls[0]));
> +
>  	for (unsigned int i = 0; i < count; ++i) {
>  		const V4L2Control *ctrl = ctrls->getByIndex(i);
>  		const V4L2ControlInfo *info = getControlInfo(ctrl->id());
> @@ -224,8 +227,10 @@ int V4L2Device::setControls(V4L2ControlList *ctrls)
>  	if (count == 0)
>  		return 0;
>
> -	const V4L2ControlInfo *controlInfo[count] = {};
> -	struct v4l2_ext_control v4l2Ctrls[count] = {};
> +	const V4L2ControlInfo *controlInfo[count];
> +	struct v4l2_ext_control v4l2Ctrls[count];
> +	memset(controlInfo, 0, count * sizeof(controlInfo[0]));
> +	memset(v4l2Ctrls, 0, count * sizeof(v4l2Ctrls[0]));
>
>  	for (unsigned int i = 0; i < count; ++i) {
>  		const V4L2Control *ctrl = ctrls->getByIndex(i);
> --
> 2.22.0
>
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> libcamera-devel at lists.libcamera.org
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