From bb5baf62e80f3ab9470fab2580e478a39eebac01 Mon Sep 17 00:00:00 2001
From: Michael Kerrisk <mtk.manpages@gmail.com>
Date: Wed, 30 Jul 2008 07:16:18 +0000
Subject: [PATCH] NOTES: Summarize the state of glibc support for exceptions
 and errno for error reporting.

---
 man7/math_error.7 | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/man7/math_error.7 b/man7/math_error.7
index 9638fe392..8662768df 100644
--- a/man7/math_error.7
+++ b/man7/math_error.7
@@ -21,7 +21,7 @@
 .\" Formatted or processed versions of this manual, if unaccompanied by
 .\" the source, must acknowledge the copyright and authors of this work.
 .\"
-.TH MATH_ERROR 7 2008-07-21 "Linux" "Linux Programmer's Manual"
+.TH MATH_ERROR 7 2008-07-30 "Linux" "Linux Programmer's Manual"
 .SH NAME
 math_error \- detecting errors from mathematical functions
 .SH SYNOPSIS
@@ -48,18 +48,6 @@ as outlined below)
 described in
 .BR fenv (3).
 
-C99 and POSIX.1-2001 specify a
-.I math_errhandling
-identifier,
-which is supposed to indicate which of these two mechanisms is in use;
-the standards require that at least one be in use,
-but permit both to be available.
-Although glibc does not support this identifier,
-in practice it supports both mechanisms.
-.\" I've tested glibc 2.3.3 and glibc 2.8, and both seem to support
-.\" both mechanisms.  A quick look at the glibc source code suggests
-.\" that support goes back to glibc 2.1 at least.  -- mtk, Jul 08
-
 A portable program that needs to check for an error from a mathematical
 function should set
 .I errno
@@ -196,8 +184,25 @@ or more leading zeros in the significand.
 .SH NOTES
 The
 .I math_errhandling
-identifier specified by C99 and POSIX.1-2001 is not supported.
+identifier specified by C99 and POSIX.1-2001 is not supported by glibc.
 .\" See CONFORMANCE in the glibc 2.8 (and earlier) source.
+This identifer is supposed to indicate which of the two
+error-notification mechanisms
+.RI ( errno ,
+exceptions retrievable via
+.BR fettestexcept (3))
+is in use.
+The standards require that at least one be in use,
+but permit both to be available.
+The current (version 2.8) situation under glibc is messy.
+Most (but not all) functions raise exceptions on errors.
+Some also set
+.IR errno .
+A few functions set
+.IR errno ,
+but don't raise an exception.
+A very few functions do neither.
+See the individual manual pages for details.
 
 To avoid the complexities of using
 .I errno