On 12/07/2018 11:56 AM, Mauro Carvalho Chehab wrote:
> A common mistake is to assume that initializing a var with:
> struct foo f = { 0 };
>
> Would initialize a zeroed struct. Actually, what this does is
> to initialize the first element of the struct to zero.
>
> According to C99 Standard 6.7.8.21:
>
> "If there are fewer initializers in a brace-enclosed
> list than there are elements or members of an aggregate,
> or fewer characters in a string literal used to initialize
> an array of known size than there are elements in the array,
> the remainder of the aggregate shall be initialized implicitly
> the same as objects that have static storage duration."
>
> So, in practice, it could zero the entire struct, but, if the
> first element is not an integer, it will produce warnings:
>
> drivers/staging/media/sunxi/cedrus/cedrus.c:drivers/staging/media/sunxi/cedrus/cedrus.c:78:49: warning: Using plain integer as NULL pointer
> drivers/staging/media/sunxi/cedrus/cedrus_dec.c:drivers/staging/media/sunxi/cedrus/cedrus_dec.c:29:35: warning: Using plain integer as NULL pointer
>
> A proper way to initialize it with gcc is to use:
>
> struct foo f = { };
>
> But that seems to be a gcc extension. So, I decided to check upstream
No, this is not a gcc extension. It's part of the latest C standard.
It's used all over in the kernel, so please use {} instead of { NULL }.
Personally I think {} is a fantastic invention and I wish C++ had it as
well.
Regards,
Hans
> what's the most commonly pattern. The gcc pattern has about 2000 entries:
>
> $ git grep -E "=\s*\{\s*\}"|wc -l
> 1951
>
> The standard-C compliant pattern has about 2500 entries:
>
> $ git grep -E "=\s*\{\s*NULL\s*\}"|wc -l
> 137
> $ git grep -E "=\s*\{\s*0\s*\}"|wc -l
> 2323
>
> So, let's initialize those structs with:
> = { NULL }
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
> ---
> drivers/staging/media/sunxi/cedrus/cedrus.c | 2 +-
> drivers/staging/media/sunxi/cedrus/cedrus_dec.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
> index b538eb0321d8..44c45c687503 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> @@ -75,7 +75,7 @@ static int cedrus_init_ctrls(struct cedrus_dev *dev, struct cedrus_ctx *ctx)
> memset(ctx->ctrls, 0, ctrl_size);
>
> for (i = 0; i < CEDRUS_CONTROLS_COUNT; i++) {
> - struct v4l2_ctrl_config cfg = { 0 };
> + struct v4l2_ctrl_config cfg = { NULL };
>
> cfg.elem_size = cedrus_controls[i].elem_size;
> cfg.id = cedrus_controls[i].id;
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> index e40180a33951..4099a42dba2d 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_dec.c
> @@ -26,7 +26,7 @@ void cedrus_device_run(void *priv)
> {
> struct cedrus_ctx *ctx = priv;
> struct cedrus_dev *dev = ctx->dev;
> - struct cedrus_run run = { 0 };
> + struct cedrus_run run = { NULL };
> struct media_request *src_req;
> unsigned long flags;
>
>
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