From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bruce Richardson <bruce.richardson@intel.com>
Subject: Re: [PATCH v3 2/4] ethdev: move error checking macros to
	header
Date: Wed, 4 Nov 2015 14:10:50 +0000
Message-ID: <20151104141050.GA19636@bricha3-MOBL3>
References: <1441811374-28984-1-git-send-email-bruce.richardson@intel.com>
 <1446552059-5446-1-git-send-email-bruce.richardson@intel.com>
 <1446552059-5446-3-git-send-email-bruce.richardson@intel.com>
 <4698587.GS9blBozDC@xps13> <20151104102418.GN3518@6wind.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
To: Thomas Monjalon <thomas.monjalon@6wind.com>, dev@dpdk.org
Return-path: <dev-bounces@dpdk.org>
Received: from mga03.intel.com (mga03.intel.com [134.134.136.65])
 by dpdk.org (Postfix) with ESMTP id 846788E91
 for <dev@dpdk.org>; Wed,  4 Nov 2015 15:10:55 +0100 (CET)
Content-Disposition: inline
In-Reply-To: <20151104102418.GN3518@6wind.com>
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

On Wed, Nov 04, 2015 at 11:24:18AM +0100, Adrien Mazarguil wrote:
> On Wed, Nov 04, 2015 at 02:19:36AM +0100, Thomas Monjalon wrote:
> > 2015-11-03 12:00, Bruce Richardson:
> > > Move the function ptr and port id checking macros to the header file, so
> > > that they can be used in the static inline functions there. In doxygen
> > > comments, mark them as for internal use only.
> > [...]
> > > +/**
> > > + * @internal
> > > + *  Macro to print a message if in debugging mode
> > > + */
> > > +#ifdef RTE_LIBRTE_ETHDEV_DEBUG
> > > +#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> > > +		RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args)
> > > +#else
> > > +#define RTE_PMD_DEBUG_TRACE(fmt, args...)
> > > +#endif
> > 
> > It does not compile because Mellanox drivers are pedantic:
> > 
> > In file included from /home/thomas/projects/dpdk/dpdk/drivers/net/mlx4/mlx4.c:78:0:
> > /home/thomas/projects/dpdk/dpdk/x86_64-native-linuxapp-gcc-shared-next/include/rte_ethdev.h: At top level:
> > /home/thomas/projects/dpdk/dpdk/x86_64-native-linuxapp-gcc-shared-next/include/rte_ethdev.h:933:38: error: ISO C does not permit named variadic macros [-Werror=variadic-macros]
> >  #define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> 
> I suggest something like the following definitions as a pedantic-proof and
> standard compliant method (one drawback being that it cannot be done with a
> single macro), see PMD_DRV_LOG() in drivers/net/mlx5/mlx5_utils.h which also
> automatically appends a line feed:
> 
>  #ifdef RTE_LIBRTE_ETHDEV_DEBUG
> 
>  #define STRIP(a, b) a
>  #define OPAREN (
>  #define CPAREN )
>  #define COMMA ,
> 
>  #define RTE_PMD_DEBUG_TRACE(...) \
>          RTE_PMD_DEBUG_TRACE_(__VA_ARGS__ STRIP OPAREN, CPAREN)
> 
>  #define RTE_PMD_DEBUG_TRACE_(fmt, ...) \
>          RTE_PMD_DEBUG_TRACE__(fmt COMMA __func__, __VA_ARGS__)
> 
>  #define RTE_PMD_DEBUG_TRACE__(...) \
>          RTE_LOG(ERR, PMD, "%s: " __VA_ARGS__)
> 
>  #else /* RTE_LIBRTE_ETHDEV_DEBUG */
> 
>  #define RTE_PMD_DEBUG_TRACE(...)
> 
>  #endif /* RTE_LIBRTE_ETHDEV_DEBUG */
> 
> STRIP() and other helper macros are used to manage the dangling comma issue
> when __VA_ARGS__ is empty as in the first call below:
> 
>  RTE_PMD_DEBUG_TRACE("foo\n");
>  RTE_PMD_DEBUG_TRACE("foo %u\n", 42);
> 
> -- 
> Adrien Mazarguil
> 6WIND

Is this really the best way around this? It looks like a lot more complicated
than the original solution. Do we really need to support the -pedantic flag
in our header files?

/Bruce