[SCM] GNU Autoconf source repository branch, master, updated. v2.63-7-gf91f917

[Eric Blake]

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- Log -----------------------------------------------------------------
commit f91f917602dad6057f335481174a8c5e28ae2252
Author: Eric Blake <address@hidden>
Date:   Sat Sep 20 16:19:40 2008 -0600

    Fix sample isinf definition.
    
    * doc/autoconf.texi (Function Portability) <isinf>: Filter out NaN
    first.
    * THANKS: Update.
    Reported by David Cournapeau.
    
    Signed-off-by: Eric Blake <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog         |    8 ++++++++
 THANKS            |    1 +
 doc/autoconf.texi |   17 +++++++++++------
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index f0feca6..c277148 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2008-09-20  Eric Blake  <address@hidden>
+
+       Fix sample isinf definition.
+       * doc/autoconf.texi (Function Portability) <isinf>: Filter out NaN
+       first.
+       * THANKS: Update.
+       Reported by David Cournapeau.
+
 2008-09-16  Eric Blake  <address@hidden>
 
        Fix Erlang regression, introduced 2006-11-17.
diff --git a/THANKS b/THANKS
index f39e949..366bf62 100644
--- a/THANKS
+++ b/THANKS
@@ -81,6 +81,7 @@ Dave Erickson               address@hidden
 Dave Love                   address@hidden
 David Byron                 address@hidden
 David Carter                address@hidden
+David Cournapeau            address@hidden
 David Fang                  address@hidden
 David J. MacKenzie          address@hidden
 David M. Lloyd              address@hidden
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 2b1d165..fa9b6ef 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -4318,7 +4318,9 @@ typically assume @code{double} arguments.  On such a 
system,
 @code{isinf} incorrectly returns true for a finite @code{long double}
 argument that is outside the range of @code{double}.
 
-To work around this porting mess, you can use code like the following.
+The best workaround for these issues is to use gnulib modules
address@hidden and @code{isnan} (@pxref{Gnulib}).  But a lighter weight
+solution involves code like the following.
 
 @smallexample
 #include <math.h>
@@ -4338,17 +4340,20 @@ static inline int isnan_ld (long double x) @{ return x 
!= x; @}
     (sizeof (x) == sizeof (long double) ? isinf_ld (x) \
      : sizeof (x) == sizeof (double) ? isinf_d (x) \
      : isinf_f (x))
-static inline int isinf_f  (float       x) @{ return isnan (x - x); @}
-static inline int isinf_d  (double      x) @{ return isnan (x - x); @}
-static inline int isinf_ld (long double x) @{ return isnan (x - x); @}
+static inline int isinf_f  (float       x)
address@hidden return !isnan (x) && isnan (x - x); @}
+static inline int isinf_d  (double      x)
address@hidden return !isnan (x) && isnan (x - x); @}
+static inline int isinf_ld (long double x)
address@hidden return !isnan (x) && isnan (x - x); @}
 #endif
 @end smallexample
 
 Use @code{AC_C_INLINE} (@pxref{C Compiler}) so that this code works on
 compilers that lack the @code{inline} keyword.  Some optimizing
 compilers mishandle these definitions, but systems with that bug
-typically have missing or broken @code{isnan} functions anyway, so it's
-probably not worth worrying about.
+typically have many other floating point corner-case compliance problems
+anyway, so it's probably not worth worrying about.
 
 @item @code{malloc}
 @c @fuindex malloc


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