Re: GCC optimizes integer overflow: bug or feature?

[Robert Dewar]

Florian Weimer wrote:
> * Paolo Bonzini:
>
> > Interesting read.  I agree with the proposed fix; however, note that
> > GCC does not make the result of overflowing signed left-shifts
> > undefined, exactly because in this case the overflow is relied upon by
> > too many existing programs
>
> Is this documented somewhere?  Without documentation, it could also be
> an oversight (lack of optimization) from a programmer perspective.

It generally seems desirable for me to have a documentation section
which takes every undefined in the standard and says what is done
with it (sort of like Annex M in the documentation for an Ada compiler).