On Sun, 5 Oct 2014 09:12:41 -0500 Jeff Epler <jep...@unpythonic.net> wrote:
> I believe that what happens is that gcc analyzes the function
>
> void sincos(double x, double *sx, double *cx)
> {
> *sx = sin(x);
> *cx = cos(x);
> }
>
> and determines that it is equivalent to the call
> sincos(x, sx, cx);
>
> at runtime, this of course becomes a nonterminating recursive call.
Hm, yes. The backtrace looked like a corrupted stack, so this sounds plausible.
> With that in mind, it seems to me that only in sincos.c is it necessary
> to avoid the use of the builtin functions. Consequently, I wonder what
> happens if you *do* fix the export of the sincos symbol, then do
> something like the below patch (untested)
Can test, when I'm back to the machine, later.
> FWIW Alec Ari has been working on what is effectively a fork of RTAI at
> https://github.com/NTULINUX/RTAI -- after some IRC discussion about what
> I think is the same issue, he ended up adding -ffreestanding to
> rtai-config --cflags, which inhibits recognition of *all* built-in
> functions except when used with the __builtin_ prefix.
Sounds like a good idea, because it essentially is freestanding.
Another thing is the sincos configure test we do.
What does it test? Userspace or kernelspace? Or both?
What happens, if I have a userspace with sincos and kernelspace without sincos
(like in my case)? Does it work correctly and compile in the workaround for
kernelspace posemath and leave it out for userspace posemath?
Please CC me in replies, so I can respond faster without reading the list.
--
Michael
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