Re: [PATCH v2] app/testpmd: fix lcore ID restriction

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 13 Jun 2024 17:51:14 +0100
Ferruh Yigit <ferruh.yigit@amd.com> wrote:

> > Hi Sivaprasad,
> > 
> > Is this '(lcoreid_t)' cast required? Because of integer promotion I
> > think result will be correct without casting.
> > 
> > (And without integer promotion considered, casting needs to be done on
> > one of the variables, not to the result, because result may be already
> > cast down I think. Anyway this is not required for this case since
> > variables are u16.)
> >  
> 
> Why casing required (for record) is,
> 'nb_txq' -> uint16_t, promoted to 'int'
> 'nb_fwd_ports' -> uint16_t, promoted to 'int'
> (nb_txq * nb_fwd_ports) -> result 'int'
> nb_fwd_lcores  -> 'uint32_t'
> 
> comparison between 'int' & 'uint32_t' gives warning. After some compiler
> version it is smart enough to not give a warning, but casting is
> required for old compilers.
> 
> And back to my comment above, casting one of the parameter to
> 'lcoreid_t' also works, as it forcing promotion to 'unsigned int'
> instead. But logically casting looks odd, so keeping casting result.

Where is the integer promotion happening?
Also would be better to use strtoul() instead of atoi() when parsing the args.
That gives better error handling and handles someone passing negative number correctly.