Re: [dpdk-dev] Build is broken in dpdk-next-net

[Neil Horman <nhorman@tuxdriver.com>]

On Fri, Mar 30, 2018 at 10:47:09PM +0800, Tonghao Zhang wrote:
> I rebuild it on ubuntu 17.10 and cash it. I use the 'RTE_SET_USED' to fix it.
> 
> 
> diff --git a/lib/librte_vhost/fd_man.c b/lib/librte_vhost/fd_man.c
> index 771675718..f11803191 100644
> --- a/lib/librte_vhost/fd_man.c
> +++ b/lib/librte_vhost/fd_man.c
> @@ -279,7 +279,8 @@ fdset_pipe_read_cb(int readfd, void *dat __rte_unused,
>                    int *remove __rte_unused)
>  {
>         char charbuf[16];
> -       read(readfd, charbuf, sizeof(charbuf));
> +       int r = read(readfd, charbuf, sizeof(charbuf));
> +       RTE_SET_USED(r);
>  }
> 
>  void
> @@ -319,5 +320,6 @@ fdset_pipe_init(struct fdset *fdset)
>  void
>  fdset_pipe_notify(struct fdset *fdset)
>  {
> -       write(fdset->u.writefd, "1", 1);
> +       int r = write(fdset->u.writefd, "1", 1);
> +       RTE_SET_USED(r);
>  }
> 

A better option might be to use _Pragma

Something like this perhaps

#define ALLOW_UNUSED(x) \
_Pragma(push) \
_Pragma(diagnostic ignored "-Wunused-result") \
#x;\
_Pragma(pop)

This is of course untested, so it probably needs some tweaking, but this method
avoids the need to declare an additional stack variable, which i don't think can
be eliminated due to the cast.  I believe that this method should also work
accross compilers (the gcc and clang compilers support this, and i think the
intel compiler should as well)

Neil