On 22-05-13 10:59:59, Kewen.Lin wrote:
> on 2022/5/13 04:16, Segher Boessenkool wrote:
> > Hi Piotr,
> > 
> > On Tue, May 03, 2022 at 12:21:12PM +0200, pkubaj@FreeBSD.org wrote:
> >> FreeBSD/powerpc* has feenableexcept() defined in fenv.h header.
> > 
> > Declared, not defined.  These are required to be real functions (on all
> > platforms that have these functions), not macros or inlines or whatever.
> > 
> 
> Piotr's reply "FreeBSD doesn't have this function in libm, it's
> implemented in /usr/include/fenv.h." from [1] made me feel like
> it's a definition instead of declaration.  So I thought the check
> should use AC_LINK_IFELSE instead, since one fenv.h which doesn't
> have the definition can still pass the proposed AC_COMPILE_IFELSE
> check.
> 
> I just did a further search, the powerpc fenv.h [2] does include
> the definition of feenableexcept.  By comparison, the x86 fenv.h [3]
> doesn't.  But I'm not sure if it's the same as what Piotr's
> environments have.  Hope it's similar. :-)
> 
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2022-April/593193.html
> [2] https://github.com/freebsd/freebsd-src/blob/main/lib/msun/powerpc/fenv.h
> [3] https://github.com/freebsd/freebsd-src/blob/main/lib/msun/x86/fenv.h

Yes, it's a definition and thanks for confirming that. As for why it's not in libm, I asked a developer about that:
03:04 <@adalava> It shouldn't be difficulted but I moved to other thing after months looking at FPE in kernel, bugs in context switch and msun test cases failing :-P

As far as I know, there are currently no plans to move it to libm on powerpc. riscv, arm and arm64 are in the same boat.

I will follow with a next patch that will check for feenableexcept() in fenv.h if libm check is unsuccessful.

Thanks,
Piotr Kubaj.

> 
> BR,
> Kewen
>