Re: powerpc-apple-darwin8.11.0 ldexpl: cannot handle zero exponents?

[Bruno Haible]

Hi Simon,

> The code reads:
> 
>     x = 1.73205L;
>     y = ldexpl (x, 0); ASSERT (y == x);
> 
> Printing the values yield:
> 
> x 1.732050 y -0.000000

Interesting...

> configure:63967: checking whether ldexpl works
> configure:64002: gcc -std=gnu99 -o conftest -g -O2 -I/opt/local/include  
> conftest.c     >&5
> configure:64006: $? = 0
> configure:64012: ./conftest
> configure:64016: $? = 0
> configure:64034: result: yes

This patch should make the test fail. Committed.

Bruno

--- m4/ldexpl.m4.orig   2008-12-09 12:56:13.000000000 +0100
+++ m4/ldexpl.m4        2008-12-09 12:55:03.000000000 +0100
@@ -1,5 +1,5 @@
-# ldexpl.m4 serial 2
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# ldexpl.m4 serial 3
+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.
@@ -60,7 +60,8 @@
   AC_SUBST([LDEXPL_LIBM])
 ])
 
-dnl Test whether ldexpl() works on finite numbers (this fails on AIX 5.1).
+dnl Test whether ldexpl() works on finite numbers (this fails on AIX 5.1
+dnl and MacOS X 10.4/PowerPC).
 AC_DEFUN([gl_FUNC_LDEXPL_WORKS],
 [
   AC_REQUIRE([AC_PROG_CC])
@@ -72,9 +73,11 @@
 extern long double ldexpl (long double, int);
 int main()
 {
-  volatile long double x = 1.0;
-  volatile long double y = ldexpl (x, -1);
-  return (y != 0.5L);
+  volatile long double x1 = 1.0;
+  volatile long double y1 = ldexpl (x1, -1);
+  volatile long double x2 = 1.73205L;
+  volatile long double y2 = ldexpl (x2, 0);
+  return (y1 != 0.5L) || (y2 != x2);
 }], [gl_cv_func_ldexpl_works=yes], [gl_cv_func_ldexpl_works=no],
       [case "$host_os" in
          aix*) gl_cv_func_ldexpl_works="guessing no";;

2008-12-09  Bruno Haible  <address@hidden>

        * m4/ldexpl.m4 (gl_FUNC_LDEXPL_WORKS): Add another check, that fails on
        MacOS X 10.4/PowerPC.
        Reported by Simon Josefsson.