Re: [Qemu-devel] [PATCH] slirp: Gcc 9 -O3 fix

[Samuel Thibault]

Dr. David Alan Gilbert, le ven. 12 avril 2019 16:49:42 +0100, a ecrit:
> * Samuel Thibault (address@hidden) wrote:
> > Hello,
> > 
> > Dr. David Alan Gilbert, le lun. 08 avril 2019 09:46:53 +0100, a ecrit:
> > > 'soread' has the comment:
> > > 
> > >         /*
> > >          * No need to check if there's enough room to read.
> > >          * soread wouldn't have been called if there weren't
> > >          */
> > >         sopreprbuf(so, iov, &n);
> > > 
> > > the compiler doesn't realise that, and is moaning about the case
> > > where the if (len <=0) return happens and the following 
> > > code tries to use iov.
> > 
> > I see. Perhaps we should make this an assert then? In case this isn't
> > true, i.e. soread() is called even if no room is available, returning 0
> > would probably just let the caller just try again, and we should rather
> > just plainly crash than hang?
> 
> Adding the assert in soread sorts that case out:
>   assert(sopreprbuf(so, iov, &n) != 0);
> 
> however, I also need to fix soreadbuf;  is it legal to call that with
> a 0 size?

It does not really make sense to, so an assert >0 should be fine.

Samuel