mingw frexp failure

[Eric Blake]

When compiling natively:

checking whether frexp() can be used without linking with libm... yes
checking whether frexp works... no

The failure is with +inf, where frexp mistakenly returns NaN instead of inf.

But when cross-compiling, mingw was omitted from the list of broken platforms.

Installing this:

From: Eric Blake <address@hidden>
Date: Tue, 4 Dec 2007 08:40:17 -0700
Subject: [PATCH] Fix frexp on mingw.

* m4/frexp.m4 (gl_FUNC_FREXP_WORKS): Detect mingw bug when
cross-compiling.
* doc/functions/frexp.texi (frexp): Document the bug.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog                |    5 +++++
 doc/functions/frexp.texi |    2 +-
 m4/frexp.m4              |    3 ++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 54a4b12..5abb766 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2007-12-04  Eric Blake  <address@hidden>
 
+       Fix frexp on mingw.
+       * m4/frexp.m4 (gl_FUNC_FREXP_WORKS): Detect mingw bug when
+       cross-compiling.
+       * doc/functions/frexp.texi (frexp): Document the bug.
+
        Make cygwin fseeko check more reliable.
        * m4/stdio_h.m4 (gl_STDIN_LARGE_OFFSET) [__CYGWIN__]: Use cygwin
        version numbers, rather than unrelated feature check.
diff --git a/doc/functions/frexp.texi b/doc/functions/frexp.texi
index cfe5996..f0a791c 100644
--- a/doc/functions/frexp.texi
+++ b/doc/functions/frexp.texi
@@ -13,7 +13,7 @@ This function does not work on denormalized numbers on some 
platforms:
 NetBSD 3.0.
 @item
 This function does not work on infinite numbers on some platforms:
-IRIX 6.5.
+IRIX 6.5, mingw.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/m4/frexp.m4 b/m4/frexp.m4
index 524f6d5..ca293b4 100644
--- a/m4/frexp.m4
+++ b/m4/frexp.m4
@@ -1,4 +1,4 @@
-# frexp.m4 serial 4
+# frexp.m4 serial 5
 dnl Copyright (C) 2007 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -126,6 +126,7 @@ int main()
 }], [gl_cv_func_frexp_works=yes], [gl_cv_func_frexp_works=no],
       [case "$host_os" in
          netbsd* | irix*) gl_cv_func_frexp_works="guessing no";;
+         mingw*)          gl_cv_func_frexp_works="guessing no";;
          *)               gl_cv_func_frexp_works="guessing yes";;
        esac
       ])
-- 
1.5.3.5