[PATCH] Enforce strict overflow checking

[Jeremy Allison]

On Tue, Apr 03, 2018 at 06:10:29PM +0200, Andreas Schneider wrote:
> On Tuesday, 3 April 2018 17:45:25 CEST Jeremy Allison wrote:
> > On Tue, Apr 03, 2018 at 02:02:53PM +0200, Andreas Schneider wrote:
> > > Ah, sorry my bad. I didn't have the tree with the reverted patch. Here we
> > > go:
> > > 
> > > 
> > > ../source3/nmbd/nmbd_incomingrequests.c: In function
> > > ‘process_node_status_request’:
> > > ../source3/nmbd/nmbd_incomingrequests.c:344:8: error: assuming pointer
> > > wraparound does not occur when comparing P +- C1 with P +- C2
> > > [-Werror=strict- overflow]
> > > 
> > >   while (buf < bufend) {
> > >   
> > >         ^
> > > 
> > > cc1: all warnings being treated as errors
> > 
> > Ah, I'm not seeing that. What version of gcc are you using ?
> 
> I'm not seeing them either with gcc 7.3.1 on my machines!
> 
> 
> I was only able to reproduce this on sn-devel (autobuild) which uses:
> 
>   gcc-4.8.real (Ubuntu 4.8.4-2ubuntu1~14.04.4) 4.8.4
> 
> > Are there a lot of these in nmbd ? Is it worth fixing nmbd
> > first, or set to ignore now and work on them later ?
> 
> I don't know. It might be after fixing that one, that it will find more in 
> that file.
> 
> However fixing this one will probably a bit tricky. The optimizer doesn't like 
> the pointer arithmetic. So you need to use array indices to do the overflow 
> calculations. By fixing that we would allow the optimizer to understand the 
> limitations better.
> 
> It is possible that gcc 7 is cleverer than 4.8 in this regard and can deal 
> with the pointer arithmetic here.
> 
> 
> 
> I hope that helps.

Sure does. RB+ and pushed all except the last two patches
that turn on the compiler shitches (or off in the nmbd
case :-).

I would like to get Metze's buy-off before pressing the
final big red button (tm) :-).

Jeremy.