diff options
Diffstat (limited to 'manual')
| -rw-r--r-- | manual/math.texi | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/manual/math.texi b/manual/math.texi index 206021c65d..72f3fda0a3 100644 --- a/manual/math.texi +++ b/manual/math.texi @@ -1313,7 +1313,9 @@ exact value passed as the input. Exceptions are raised appropriately for this value and in accordance with IEEE 754 / ISO C / POSIX semantics, and it is then rounded according to the current rounding direction to the result that is returned to the user. @code{errno} -may also be set (@pxref{Math Error Reporting}). +may also be set (@pxref{Math Error Reporting}). (The ``inexact'' +exception may be raised, or not raised, even if this is inconsistent +with the infinite-precision value.) @item For the IBM @code{long double} format, as used on PowerPC GNU/Linux, @@ -1344,11 +1346,16 @@ subnormal (in each case, with the correct sign), according to the current rounding direction and with the underflow exception raised. @item -Where the mathematical result underflows and is not exactly -representable as a floating-point value, the underflow exception is -raised (so there may be spurious underflow exceptions in cases where -the underflowing result is exact, but not missing underflow exceptions -in cases where it is inexact). +Where the mathematical result underflows (before rounding) and is not +exactly representable as a floating-point value, the function does not +behave as if the computed infinite-precision result is an exact value +in the subnormal range. This means that the underflow exception is +raised other than possibly for cases where the mathematical result is +very close to the underflow threshold and the function behaves as if +it computes an infinite-precision result that does not underflow. (So +there may be spurious underflow exceptions in cases where the +underflowing result is exact, but not missing underflow exceptions in +cases where it is inexact.) @item @Theglibc{} does not aim for functions to satisfy other properties of |