Paul Eggert wrote:
> > How does that sound? (It's a lot of work, I know.)
>
> It sounds nice. You're right that it's a lot of work, though.
> Is it worth the effort? (Depends on the problem you want solved
> but I don't know what that is....)
The problem is that the way to test whether a math function ran into an
exceptional case is platform dependent. For example, after
y = sqrt (x);
some platforms require
if (isnan (y))
on others it's
if (fetestexcept (FE_INVALID))
and on others it's
if (errno == EDOM)
On some platforms, two or all three among these codes work. But none
of these three codes works on all platforms.
> Will the <fenv.h> replacement address the documented FLT_ROUNDS
> incompatibility between C99 and typical GNU platforms?
Yes, by making fegetround() available on all platforms, the problem
is addressed: We will be able to recommend to use the <fenv.h> API
everywhere.
Oh, btw, the FLT_ROUNDS incompatibility was not yet documented. Done
as follows:
2011-11-06 Bruno Haible <br...@clisp.org>
Doc about floating-point and math API.
* doc/posix-headers/float.texi: Mention problem with FLT_ROUNDS.
* doc/posix-headers/math.texi: Mention problem with math_errhandling.
--- doc/posix-headers/float.texi.orig Mon Nov 7 00:21:04 2011
+++ doc/posix-headers/float.texi Mon Nov 7 00:21:00 2011
@@ -25,4 +25,8 @@
Portability problems not fixed by Gnulib:
@itemize
+@item
+The macro @code{FLT_ROUNDS} is a constant expression and does not represent
+the current rounding mode on some platforms:
+glibc 2.11, HP-UX 11, mingw.
@end itemize
--- doc/posix-headers/math.texi.orig Mon Nov 7 00:21:04 2011
+++ doc/posix-headers/math.texi Mon Nov 7 00:12:10 2011
@@ -32,4 +32,7 @@
@item
@code{NAN} is not a compile time constant with some compilers:
OSF/1 with Compaq (ex-DEC) C 6.4.
+@item
+The macro or variable @code{math_errhandling} is not defined on some platforms:
+glibc 2.11, OpenBSD 4.9, NetBSD 5.1, UP-UX 11, IRIX 6.5, OSF/1 5.1, Cygwin
1.7.9, mingw, MSVC 9.
@end itemize
--
In memoriam Louis Philippe d'Orléans
<http://en.wikipedia.org/wiki/Louis_Philippe_II,_Duke_of_Orléans>
