[dpdk-dev] [PATCH] librte_eal: fix wrong args operation in eal_parse_args

[Richardson, Bruce]

> -----Original Message-----
> From: Yang, Ziye
> Sent: Wednesday, May 11, 2016 12:51 PM
> To: Richardson, Bruce <bruce.richardson at intel.com>
> Cc: dev at dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] librte_eal: fix wrong args operation in
> eal_parse_args
> 
> Hi Bruce,
> 
> Could it be fixed later?  If not, it should be documented. I faced this
> issued today, and found that dpdk changed my last arg.  In my mind, dpdk
> should not change the argv[last], which will confuse the users.
> 

We can certainly consider changing it, but I am concerned about stability of existing apps. I think it needs some discussion and consensus on-list before a change like this is made.

For right now, definitely the behavior should be documented. Would you consider submitting a documentation update patch for this issue instead of this code change?

Thanks,
/Bruce

> Best Regards,
> Ziye Yang
> 
> -----Original Message-----
> From: Richardson, Bruce
> Sent: Wednesday, May 11, 2016 7:25 PM
> To: Yang, Ziye <ziye.yang at intel.com>
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] librte_eal: fix wrong args operation in
> eal_parse_args
> 
> On Wed, May 11, 2016 at 01:28:21PM +0800, Ziye Yang wrote:
> > This patch is used to fix wrong operation on user input args.
> > eal_parse_args function should not operate the args passed by the
> > user. If the element in argv is generated by malloc function, changing
> > it  will cause memory issues when free the args.
> >
> > Signed-off-by: Ziye Yang <ziye.yang at intel.com>
> > ---
> >  lib/librte_eal/bsdapp/eal/eal.c   | 2 --
> >  lib/librte_eal/linuxapp/eal/eal.c | 2 --
> >  2 files changed, 4 deletions(-)
> >
> > diff --git a/lib/librte_eal/bsdapp/eal/eal.c
> > b/lib/librte_eal/bsdapp/eal/eal.c index 06bfd4e..0eef92d 100644
> > --- a/lib/librte_eal/bsdapp/eal/eal.c
> > +++ b/lib/librte_eal/bsdapp/eal/eal.c
> > @@ -420,8 +420,6 @@ eal_parse_args(int argc, char **argv)
> >  		goto out;
> >  	}
> >
> > -	if (optind >= 0)
> > -		argv[optind-1] = prgname;
> >  	ret = optind-1;
> >
> >  out:
> > diff --git a/lib/librte_eal/linuxapp/eal/eal.c
> > b/lib/librte_eal/linuxapp/eal/eal.c
> > index 8aafd51..ba9d1ac 100644
> > --- a/lib/librte_eal/linuxapp/eal/eal.c
> > +++ b/lib/librte_eal/linuxapp/eal/eal.c
> > @@ -658,8 +658,6 @@ eal_parse_args(int argc, char **argv)
> >  		goto out;
> >  	}
> >
> > -	if (optind >= 0)
> > -		argv[optind-1] = prgname;
> >  	ret = optind-1;
> >
> >  out:
> This is a behaviour change in DPDK. The behaviour has always been that
> after calling eal init, you can update your argv/argc values by the number
> of args parsed and then parse your app args as normal, since argv[0] will
> still point to your program name. While I agree that having the current
> behaviour may cause some problems, changing this behaviour may break
> applications that have been written to use the existing behaviour.
> 
> Since it is only the last EAL parameter arg that is modified, I think it
> would be acceptable to have the behaviour well documented and then expect
> any app to store a second copy of the pointer to be modified if it is
> needed for a subsequent free call, for example.
> 
> /Bruce