Messages in this thread | | | Date | Mon, 24 Oct 2022 10:43:52 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 1/1] linux/container_of.h: Warn about loss of constness |
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On Mon, Oct 24, 2022 at 11:26:10AM +0300, Sakari Ailus wrote: > container_of() casts the original type to another which leads to the loss > of the const qualifier if it is not specified in the caller-provided type. > This easily leads to container_of() returning a non-const pointer to a > const struct which the C compiler does not warn about. > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> > --- > include/linux/container_of.h | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/include/linux/container_of.h b/include/linux/container_of.h > index 2f4944b791b81..c7c21d0f41a87 100644 > --- a/include/linux/container_of.h > +++ b/include/linux/container_of.h > @@ -13,6 +13,10 @@ > * @type: the type of the container struct this is embedded in. > * @member: the name of the member within the struct. > * > + * WARNING: as container_of() casts the given struct to another, also the
No need for "also" here (sorry for the grammar nit.)
> + * possible const qualifier of @ptr is lost unless it is also specified in > + * @type. This is not a problem if the containing object is not const. Use with > + * care.
I do not think these last two sentences you added here are needed either.
> */ > #define container_of(ptr, type, member) ({ \ > void *__mptr = (void *)(ptr); \ > @@ -27,6 +31,11 @@ > * @type: the type of the container struct this is embedded in. > * @member: the name of the member within the struct. > * > + * WARNING: as container_of() casts the given struct to another, also the > + * possible const qualifier of @ptr is lost unless it is also specified in > + * @type. This is not a problem if the containing object is not const. Use with > + * care.
Same comments here.
thanks,
greg k-h
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