Re: [PATCH 0/3] cmd: setexpr: add fmt format string operation

["Marek Behún" <marek.behun@nic.cz>]

On Wed, 30 Jun 2021 12:17:47 -0400
Sean Anderson <seanga2@gmail.com> wrote:

> On 6/29/21 11:13 AM, Wolfgang Denk wrote:
> > Dear Sean,
> > 
> > In message <19b6eeea-2aad-972b-aeeb-8959aab17d7a@gmail.com> you
> > wrote:  
> >>
> >> The issue with this is twofold. First, there is no portable way to
> >> construct a va_list from C code. So the likely way to do this
> >> would be to set an arbitrary limit, and then just pass the
> >> arguments in. E.g. something like  
> > 
> > We already have an argument list: it's what's being passed to the
> > "setexpr" command, minus the initial arguments.
> >   
> >> 	snprintf(buf, sizeof(buf), argv[3], argc >= 4 ? argv[4] :
> >> NULL, /* etc */);  
> > 
> > Why this test on argc?  If it's less than 4, argv[4] should be NULL
> > anyway.  
> 
> 	snprintf(buf, sizeof(buf), argv[3], argc >= 4 ? argv[4] :
> NULL, argc >= 5 ? argv[5] : NULL, argc >= 6 ? argv[6] : NULL, /* etc
> */);

This is insane. The argv[]s are strings. What if I use "%08x" as format,
and pass "123" as argument?? It would print pointer to the string.

Clearly this needs its own implementation...

Marek