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

["Richardson, Bruce" <bruce.richardson@intel.com>]

> -----Original Message-----
> From: Yang, Ziye
> Sent: Wednesday, May 11, 2016 2:39 PM
> To: Richardson, Bruce <bruce.richardson@intel.com>
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] librte_eal: fix wrong args operation in
> eal_parse_args
> 
> Hi Bruce,
> 
> Could you tell me the documentation file name? Then I can conduct the
> following documentation relate d patch.

The behavior is already documented in the doxygen API definitions for rte_eal_init().

* @return$
 *   - On success, the number of parsed arguments, which is greater or$
 *     equal to zero. After the call to rte_eal_init(),$
 *     all arguments argv[x] with x < ret may be modified and should$
 *     not be accessed by the application.$
 *   - On failure, a negative error value.$

However, maybe you want to call it out in a different way to make it clearer for those using the functions. Other than that, perhaps look in the programmers guide document to see if it needs a mention there - or a reference to the API doc.

/Bruce

PS: When replying, please respond below existing emails, rather than top-posting. Thanks.

> 
> -----Original Message-----
> From: Richardson, Bruce
> Sent: Wednesday, May 11, 2016 8:21 PM
> To: Yang, Ziye <ziye.yang@intel.com>
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] librte_eal: fix wrong args operation in
> eal_parse_args
> 
> 
> 
> > -----Original Message-----
> > From: Yang, Ziye
> > Sent: Wednesday, May 11, 2016 12:51 PM
> > To: Richardson, Bruce <bruce.richardson@intel.com>
> > Cc: dev@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@intel.com>
> > Cc: dev@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@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