[Vm-dev] Re: I need help building Cog on 64bit Linux (new Squeak server)

[Nicolas Cellier]

2013/1/28 Ken Causey <ken at kencausey.com>:
>
> Eliot said:
>>
>> Hmmm.  Sorry to put you to this but what happens when you run the r2669,
>> r2672 and r2673 VMs from http://www.mirandabanda.org/files/Cog/VM/? If
>> these don't crash then it might be something to do with gcc 4.4.x.  But
>> I'd
>> have to take a look, and time is tight right now...  But if any of them do
>> work could you use them for the interim?
>
>
> Not a problem and thanks for the reply.
>
> Well I started with 2673 and the tests are still running but it would have
> crashed by now if the same problem exists so it's looking like the gcc
> version is the issue.  I will try earlier gcc versions and report back.
>
> It's a little disheartening that in this day and age we are tickling gcc
> issues when the same version of gcc is used to build the kernel and
> thousands upon thousands of Debian binaries which (by and large anyway) seem
> to be fine.
>
> Ken

And the answer would be: don't rely on UB (Undefined Behavior)
Modern interpretation of the standards is that a compiler has a
license to ignore UB in order to perform optimizations... This is
because no one should rely on UB.
Unfortunately, the underlying C language is full of UB, and the signed
arithmetic model is particularly broken...

I doubt the thousands of packages have been working unchanged...
They work with army of programmers maintaining the code and chasing
the compiler warnings.
As long as we ignore the warnings, we are in danger.
As long as we have several hundreds warnings, there is no easy way to
analyze their dangerosity...

Nicolas