[perl #133495] perl-5.28.0 fails to build on Solaris 10

On Thu, 17 Jan 2019 07:36:42 -0800, LeonT wrote:
> On Thu, Jan 17, 2019 at 9:26 AM Fabian Groffen via RT
> <perlbug-followup@perl.org> wrote:
> > I think that the GCC compiler is actually doing "too smart" things
> > here when optimisations are enabled.
> >
> > /usr/sfw/bin/gcc -O2 -> 4
> > gcc-6.4.0 -O2 -> 4
> > gcc-7.3.0 -O2 -> 4
> > gcc-8.2.0 -O2 -> 0
> > /usr/sfw/bin/gcc -g -> 4
> > gcc-6.4.0 -g -> 4
> > gcc-7.3.0 -g -> 4
> > gcc-8.2.0 -g -> 4
> >
> > Behaviour seems to be pretty much limited to gcc-8.2 while optimising
> > at the moment.
> 
> Yeah. I guess that means we need a better test that confuses the
> compiler a little bit more. One would expect volatile to take care of
> that but apparently not; The C standard is notoriously fuzzy on
> volatiles (C99 6.7.6).
> 
> What happens if you put the array outside the function?

The results are the same, unfortunately.

> 
> > Yes, including the fact that at the time I compiled 5.26.2, I used
> > GCC-7.3, which produced the correct result for the unaligned check.
> >
> > This makes me wonder what the problem of OP is, though.  His env
> > seems to suggest using GCC-4.9, which I don't have anymore for
> > verification of the results.
> 
> They did use -O3, so I guess that always enabled that optimization.

It seems you're correct about that (code from original test):

/usr/sfw/bin/gcc -O3 -> 4
gcc-6.4.0 -O3 -> 0
gcc-7.3.0 -O3 -> 0
gcc-8.2.0 -O3 -> 0
/usr/sfw/bin/gcc -O2 -> 4
gcc-6.4.0 -O2 -> 4
gcc-7.3.0 -O2 -> 4
gcc-8.2.0 -O2 -> 0
/usr/sfw/bin/gcc -g -> 4
gcc-6.4.0 -g -> 4
gcc-7.3.0 -g -> 4
gcc-8.2.0 -g -> 4

Fabian

---
via perlbug:  queue: perl5 status: open
https://rt.perl.org/Ticket/Display.html?id=133495

• [perl #133495] perl-5.28.0 fails to build on Solaris 10 by Fabian Groffen via RT