frexp: test for NetBSD failure on -0.0

* m4/frexp.m4 (gl_FUNC_FREXP_WORKS): Enhance test, since some, but
not all, bugs from NetBSD 3.0 have been fixed.
* doc/posix-functions/frexp.texi (frexp): Document bug.
Reported by Thomas Klausner.

Signed-off-by: Eric Blake <ebb9@byu.net>

diff --git a/ChangeLog b/ChangeLog
index bf7fcc9..414b8e4 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2008-09-12  Eric Blake  <ebb9@byu.net>
 
+       frexp: test for NetBSD failure on -0.0
+       * m4/frexp.m4 (gl_FUNC_FREXP_WORKS): Enhance test, since some, but
+       not all, bugs from NetBSD 3.0 have been fixed.
+       * doc/posix-functions/frexp.texi (frexp): Document bug.
+       Reported by Thomas Klausner.
+
        signbit: work around bug of HP-UX 10.20 cc with -0.0 literal
        * m4/signbit.m4 (gl_SIGNBIT_TEST_PROGRAM): Rewrite test to avoid
        literal -0.0.

diff --git a/doc/posix-functions/frexp.texi b/doc/posix-functions/frexp.texi
index f0a791c..345ce74 100644 (file)
--- a/doc/posix-functions/frexp.texi
+++ b/doc/posix-functions/frexp.texi
@@ -12,6 +12,9 @@ Portability problems fixed by Gnulib:
 This function does not work on denormalized numbers on some platforms:
 NetBSD 3.0.
 @item
+This function does not work on negative zero on some platforms:
+NetBSD 4.99.
+@item
 This function does not work on infinite numbers on some platforms:
 IRIX 6.5, mingw.
 @end itemize

diff --git a/m4/frexp.m4 b/m4/frexp.m4
index ce031e7..11ed059 100644 (file)
--- a/m4/frexp.m4
+++ b/m4/frexp.m4
@@ -1,5 +1,5 @@
-# frexp.m4 serial 5
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# frexp.m4 serial 6
+dnl Copyright (C) 2007, 2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -88,7 +88,8 @@ AC_DEFUN([gl_FUNC_FREXP_NO_LIBM],
 ])
 
 dnl Test whether frexp() works also on denormalized numbers (this fails e.g. on
-dnl NetBSD 3.0) and on infinite numbers (this fails e.g. on IRIX 6.5 and mingw).
+dnl NetBSD 3.0), on infinite numbers (this fails e.g. on IRIX 6.5 and mingw),
+dnl and on negative zero (this fails e.g. on NetBSD 4.99).
 AC_DEFUN([gl_FUNC_FREXP_WORKS],
 [
   AC_REQUIRE([AC_PROG_CC])
@@ -98,10 +99,14 @@ AC_DEFUN([gl_FUNC_FREXP_WORKS],
       AC_TRY_RUN([
 #include <float.h>
 #include <math.h>
+#include <string.h>
 int main()
 {
   int i;
   volatile double x;
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   So we use -zero instead.  */
+  double zero = 0.0;
   /* Test on denormalized numbers.  */
   for (i = 1, x = 1.0; i >= DBL_MIN_EXP; i--, x *= 0.5)
     ;
@@ -122,6 +127,14 @@ int main()
     if (y != x)
       return 1;
   }
+  /* Test on negative zero.  */
+  x = -zero;
+  {
+    int exp;
+    double y = frexp (x, &exp);
+    if (memcmp (&y, &x, sizeof x))
+      return 1;
+  }
   return 0;
 }], [gl_cv_func_frexp_works=yes], [gl_cv_func_frexp_works=no],
       [case "$host_os" in