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Document sNaN argument error handling.

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TS 18661-1 says that "Whether a signaling NaN input causes a domain
error is implementation-defined.".  Considering it a domain error
would (given glibc's math_errhandling definition) mean setting errno
to EDOM.  glibc consistently does not set errno for sNaN inputs
(unless it does so for qNaN as well, i.e. iseqsig), so this patch adds
documentation of the implementation-defined choice not to treat this
case as a domain error.

	* manual/arith.texi (Math Error Reporting): Document that sNaN
	arguments are not considered domain errors.
This commit is contained in:
Joseph Myers 2016-12-16 23:41:00 +00:00
parent ea1bd74def
commit 3fdf17926c
2 changed files with 10 additions and 0 deletions
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@ -1,3 +1,8 @@
2016-12-16 Joseph Myers <joseph@codesourcery.com>
* manual/arith.texi (Math Error Reporting): Document that sNaN
arguments are not considered domain errors.
2016-12-16 Zack Weinberg <zackw@panix.com>
Florian Weimer <fweimer@redhat.com>
Nick Mathewson <nickm@torproject.org>

5
manual/arith.texi
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@ -939,6 +939,11 @@ guaranteed; it is intended that @theglibc{} should set it when the
underflow is to an appropriately signed zero, but not necessarily for
other underflows.
When a math function has an argument that is a signaling NaN,
@theglibc{} does not consider this a domain error, so @code{errno} is
unchanged, but the invalid exception is still raised (except for a few
functions that are specified to handle signaling NaNs differently).
Some of the math functions are defined mathematically to result in a
complex value over parts of their domains. The most familiar example of
this is taking the square root of a negative number. The complex math