On Fri, May 13, 2022 at 12:34:05PM +0200, Piotr Kubaj wrote: > On 22-05-13 10:59:59, Kewen.Lin wrote: > > on 2022/5/13 04:16, Segher Boessenkool wrote: > > > On Tue, May 03, 2022 at 12:21:12PM +0200, pku...@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.
FreeBSD's own documentation (<https://www.freebsd.org/cgi/man.cgi?query=feenableexcept>) says it is a function, and it suggests it is in the standard library even. This would be as expected, the same holds for the similar C standard functions. This <fenv.h> does not provide an external definition, only a static inline (this is a good thing for a header file of course). You can take the address of a function. You also can interpose a real function normally, but that may not be relevant for FreeBSD, no idea. You can do neither with a static inline. So this should probably be fixed? Thanks for explaining the situation better! Segher
