Re: [lwip-devel] [bug #27445] PCB hangs in Fast Retransmit due to unchanging cwnd

[Alain Mouette]

Bill Auerbach escreveu:
> Follow-up Comment #4, bug #27445 (project lwip):
>
> if ((u16_t)(pcb->cwnd + pcb->mss) > pcb->cwnd) { ... }
>
> > From a coding standpoint, the 2 variables are u16_t and the cast has no
> effect.  From a runtime standpoint, is the cast always correct?  
>
> If the addition could overflow, the test fails.  You should then cast to
> u32_t.  But I don't think those values can ever cause an overflow.
>
> Maybe I'm picky - when I see a cast I think "we're changing what the compiler
> will normally do".  In this case we're not and at worse, could fail on an
> overflow.

I allways cast to signed:
 if (( (int16_t)((pcb->cwnd + pcb->mss) - pcb->cwnd) ) >0) { ... }
allways with lots of parentesis just to make sure that no optimyser gets 
in the way

This should allways work without using 32bits un-nessessarily

Alain