Re: [dpdk-dev] [PATCH 2/3] crypto: fix pedentic compilation errors

[Nelio Laranjeiro <nelio.laranjeiro@6wind.com>]

Hi Pablo,

On Wed, Nov 22, 2017 at 09:48:47AM +0000, De Lara Guarch, Pablo wrote:
> Hi Nelio,
> 
> > -----Original Message-----
> > From: Nelio Laranjeiro [mailto:nelio.laranjeiro@6wind.com]
> > Sent: Wednesday, November 22, 2017 8:10 AM
> > To: Akhil Goyal <akhil.goyal@nxp.com>; Doherty, Declan
> > <declan.doherty@intel.com>
> > Cc: dev@dpdk.org; De Lara Guarch, Pablo
> > <pablo.de.lara.guarch@intel.com>; stable@dpdk.org
> > Subject: [PATCH 2/3] crypto: fix pedentic compilation errors
> > 
> >  /root/dpdk/x86_64-native-linuxapp-gcc/include/rte_crypto.h:126:28:
> > error: ISO C forbids zero-size array ‘sym’ [-Werror=pedantic]
> >    struct rte_crypto_sym_op sym[0];
> >                             ^~~
> > 
> > Fixes: d2a4223c4c6d ("cryptodev: do not store pointer to op specific
> > params")
> > Cc: pablo.de.lara.guarch@intel.com
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
> > ---
> >  lib/librte_cryptodev/rte_crypto.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/lib/librte_cryptodev/rte_crypto.h
> > b/lib/librte_cryptodev/rte_crypto.h
> > index 3d672fe7d..dc6e91d1d 100644
> > --- a/lib/librte_cryptodev/rte_crypto.h
> > +++ b/lib/librte_cryptodev/rte_crypto.h
> > @@ -123,7 +123,7 @@ struct rte_crypto_op {
> > 
> >  	RTE_STD_C11
> >  	union {
> > -		struct rte_crypto_sym_op sym[0];
> > +		struct rte_crypto_sym_op *sym;
> 
> This would add extra 64 bits that are not necessary,
> as the rte_crypto_sym_op structure is always placed after rte_crypto_op
> (this is just a marker).
> 
> Is there any other way to fix this error?

Indeed it is not the correct solution, the point here is RTE_STD_C11 is
wrongly used because even in C11 arrays with size of 0 are not
allowed.  If it was the last attribute of the structure it could have
been replaced with empty brackets but as it is inside an union, it
cannot.  The correct solution is to replace the RTE_STD_C11 by
__extension__.

> Which compiler are you using?

It occurs with any compiler when you enable the pedantic flag under C11.
All DPDK headers have been fix to avoid such issue [1].

Thanks,

[1] http://dpdk.org/ml/archives/dev/2016-April/037051.html

-- 
Nélio Laranjeiro
6WIND