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Minor corrections and clarifications regarding exceptions.

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This commit is contained in:
David Schultz 2011-10-21 14:23:59 +00:00
parent b39ba076ec
commit 1f52bcdde4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=226618
1 changed files with 23 additions and 12 deletions
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35
lib/msun/man/fenv.3
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@ -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