[Boost-commit] svn:boost r86711 - trunk/boost/math/tools

Subject: [Boost-commit] svn:boost r86711 - trunk/boost/math/tools
From: john_at_[hidden]
Date: 2013-11-15 13:24:31

Author: johnmaddock
Date: 2013-11-15 13:24:31 EST (Fri, 15 Nov 2013)
New Revision: 86711
URL: http://svn.boost.org/trac/boost/changeset/86711

Log:
Add comments and fixes to FPU flags manipulation.

Text files modified: 
   trunk/boost/math/tools/config.hpp |    14 +++++++++++++-                          
   1 files changed, 13 insertions(+), 1 deletions(-)

Modified: trunk/boost/math/tools/config.hpp
==============================================================================
--- trunk/boost/math/tools/config.hpp	Fri Nov 15 12:31:07 2013	(r86710)
+++ trunk/boost/math/tools/config.hpp	2013-11-15 13:24:31 EST (Fri, 15 Nov 2013)	(r86711)
@@ -285,7 +285,19 @@
 
 }} // namespace boost namespace math
 
-#if ((defined(__linux__) && !defined(__UCLIBC__)) || defined(__QNX__) || defined(__IBMCPP__)) && !defined(BOOST_NO_FENV_H)
+#ifdef __GLIBC_PREREQ
+#  if __GLIBC_PREREQ(2,14)
+#     define BOOST_MATH_HAVE_FIXED_GLIBC
+#  endif
+#endif
+
+#if ((defined(__linux__) && !defined(__UCLIBC__) && !defined(BOOST_MATH_HAVE_FIXED_GLIBC)) || defined(__QNX__) || defined(__IBMCPP__)) && !defined(BOOST_NO_FENV_H)
+//
+// This code was introduced in response to this glibc bug: http://sourceware.org/bugzilla/show_bug.cgi?id=2445
+// Basically powl and expl can return garbage when the result is small and certain exception flags are set
+// on entrance to these functions.  This appears to have been fixed in Glibc 2.14 (May 2011).
+// Much more information in this message thread: https://groups.google.com/forum/#!topic/boost-list/ZT99wtIFlb4
+//
 
    #include <boost/detail/fenv.hpp>