diff options
| -rw-r--r-- | lib/msun/man/fenv.3 | 35 |
1 files changed, 23 insertions, 12 deletions
diff --git a/lib/msun/man/fenv.3 b/lib/msun/man/fenv.3 index aaea5f5..6fee216 100644 --- a/lib/msun/man/fenv.3 +++ b/lib/msun/man/fenv.3 @@ -91,24 +91,35 @@ The following macros expand to bit flags of type representing the five standard floating-point exceptions. .Bl -tag -width ".Dv FE_DIVBYZERO" .It Dv FE_DIVBYZERO -A divide-by-zero exception occurs when the program attempts to -divide a finite non-zero number by zero. +A divide-by-zero exception occurs when the +.Em exact +result of a computation is infinite (according to the limit definition). +For example, dividing a finite non-zero number by zero or computing +.Fn log 0 +raises a divide-by-zero exception. .It Dv FE_INEXACT -An inexact exception is raised whenever there is a loss of precision +An inexact exception is raised whenever there is a loss of accuracy due to rounding. .It Dv FE_INVALID Invalid operation exceptions occur when a program attempts to perform calculations for which there is no reasonable representable answer. -For instance, subtraction of infinities, division of zero by zero, -ordered comparison involving \*(Nas, and taking the square root of a +For instance, subtraction of like-signed infinities, division of zero by zero, +ordered comparison involving \*(Nas, and taking the real square root of a negative number are all invalid operations. .It Dv FE_OVERFLOW -An overflow exception occurs when the magnitude of the result of a -computation is too large to fit in the destination type. +In contrast with divide-by-zero, +an overflow exception occurs when an infinity is produced because +the magnitude of the exact result is +.Em finite +but too large to fit in the destination type. +For example, computing +.Li DBL_MAX * 2 +raises an overflow exception. .It Dv FE_UNDERFLOW -Underflow occurs when the result of a computation is too close to zero -to be represented as a non-zero value in the destination type. +Underflow occurs when the result of a computation loses precision +because it is too close to zero. +The result is a subnormal number or zero. .El .Pp Additionally, the @@ -183,9 +194,9 @@ as usual, but no .Dv SIGFPE signals will be generated as a result. Non-stop mode is the default, but it may be altered by -non-standard mechanisms. -.\" XXX Mention fe[gs]etmask() here after the interface is finalized -.\" XXX and ready to be officially documented. +.Fn feenableexcept +and +.Fn fedisableexcept . The .Fn feupdateenv function restores a saved environment similarly to |
