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Diffstat (limited to 'manual/arith.texi')
| -rw-r--r-- | manual/arith.texi | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/manual/arith.texi b/manual/arith.texi index f9296a362e..41ab577237 100644 --- a/manual/arith.texi +++ b/manual/arith.texi @@ -720,6 +720,20 @@ These macros, defined by TS 18661-1:2014, are constant expressions for signaling NaNs. @end deftypevr +@comment fenv.h +@comment ISO +@deftypevr Macro int FE_SNANS_ALWAYS_SIGNAL +This macro, defined by TS 18661-1:2014, is defined to @code{1} in +@file{fenv.h} to indicate that functions and operations with signaling +NaN inputs and floating-point results always raise the invalid +exception and return a quiet NaN, even in cases (such as @code{fmax}, +@code{hypot} and @code{pow}) where a quiet NaN input can produce a +non-NaN result. Because some compiler optimizations may not handle +signaling NaNs correctly, this macro is only defined if compiler +support for signaling NaNs is enabled. That support can be enabled +with the GCC option @option{-fsignaling-nans}. +@end deftypevr + @w{IEEE 754} also allows for another unusual value: negative zero. This value is produced when you divide a positive number by negative infinity, or when a negative result is smaller than the limits of |