[PATCH v2] newlib: fix build with <gcc-5 versions

[Corinna Vinschen]

On Mar 18 09:30, R. Diez via Newlib wrote:
> 
> > > It's not just about old GCC, it's about any C compiler that doesn't have
> > > that builtin.
> > 
> > Well, I guess, GTG then.
> 
> 
> Let's see if I understand the situation:
> 
> You are committing a replacement implementation of __builtin_mul_overflow() for older GCC versions and for any other compiler which does not have it.
> 
> The only significant extra feature about that function is the detection of integer overflow.
> 
> The implementation lives in libc/include/sys/cdefs.h , so it is
> accessible not just by some special malloc code which should never
> overflow because targets wouldn't have that much memory or whatever.
> 
> The replacement implementation is known to be broken and therefore poses a risk on anybody relying on the original, documented behaviour.
> 
> There are no mitigation measures. There is not even a comment next to the replacement implementation that states it is broken.
> 
> And you guys are fine with that.
> 
> Is that correct?

I'm open to a better or followup patch.


Corinna