On Aug 15 12:59, J.H. van de Water wrote: > By excluding the denormal-operand exception from FE_ALL_EXCEPT, it will not > be possible anymore to UNmask this exception by means of the API defined by > /usr/include/fenv.h > > Note: terminology has changed since IEEE Std 854-1987; denormalized numbers > are called subnormal numbers nowadays. > > This modification has basically been motivated by the fact that it is also > not possible on Linux to manipulate the denormal-operand exception by means > of the interface as defined by /usr/include/fenv.h. This has been the state > of affairs on Linux since 2001 (Andreas Jaeger). > > The exceptions required by the standard (IEEE Std 754), in case they can be > supported by the implementation, are: > FE_INEXACT, FE_UNDERFLOW, FE_OVERFLOW, FE_DIVBYZERO and FE_INVALID. > > Although it is allowed to define additional exceptions, there is no reason > to support the "denormal-operand exception" in this case (fenv.h), because > the subnormal numbers can be handled almost as fast the normalized numbers > by the hardware of the x86/x86_64 architecture. Said differently, a reason > to trap on the input of subnormal numbers does not exist. At least that is > what William Kahan and others at Intel asserted around 2000. > (that is William Kahan of the K-C-S draft, the precursor to the standard) > > This commit modifies winsup/cygwin/include/fenv.h as follows: > - redefines FE_ALL_EXCEPT from 0x3f to 0x3d > - removes the definition for FE_DENORMAL > - introduces __FE_DENORM (0x2) (enum in Linux also uses __FE_DENORM) > - introduces FE_ALL_EXCEPT_X86 (0x3f), i.e. ALL x86/x86_64 FP exceptions
Shouldn't FE_ALL_EXCEPT_X86 be defined locally in fenv.cc only? I don't see that Linux exports that definition. Thanks, Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
signature.asc
Description: PGP signature
