lkml.org 
[lkml]   [2022]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/1] linux/container_of.h: Warn about loss of constness
    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

    \
     
     \ /
      Last update: 2022-10-24 10:45    [W:2.865 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site