Re: AC_C_LONG_DOUBLE is wrong on IRIX 5.3

[Oliver Kiddle]

Paul Eggert wrote:
> 
> Thanks.  I have some further remarks:

I've attached the patch reflecting these remarks.

Hopefully that issue I mentioned with gcc 2.95.2's float.h doesn't
apply to any compiler that lacks long double or has a small long
double. If it does we'll have to think again.

> Reword to 'Define if long double has greater range or precision than double.'
> Then it'll fit on a line.

Not with out reducing the indentation.

> Can you please test and resubmit a patch along those lines?

I've not been able to test this on IRIX 5.3 or any machine lacking a
long double but I will do that in a couple of weeks when I return.

Oliver

--- lib/autoconf/c.m4   Sat Sep 22 16:28:27 2001
+++ lib/autoconf/c.m4   Fri Nov 16 17:07:16 2001
@@ -828,25 +828,26 @@
 # AC_C_LONG_DOUBLE
 # ----------------
 AC_DEFUN([AC_C_LONG_DOUBLE],
-[AC_CACHE_CHECK(for long double, ac_cv_c_long_double,
+[AC_CACHE_CHECK(for long double with greater range or precision than double,
+ac_cv_c_long_double,
 [if test "$GCC" = yes; then
   ac_cv_c_long_double=yes
 else
-AC_TRY_RUN(
-[int
+AC_TRY_COMPILE(
+[#include <float.h>
+int
 main ()
 {
   /* The Stardent Vistra knows sizeof(long double), but does not
      support it.  */
   long double foo = 0.0;
-  /* On Ultrix 4.3 cc, long double is 4 and double is 8.  */
-  exit (sizeof (long double) < sizeof (double));
+  int a[DBL_MAX < LDBL_MAX || LDBL_EPSILON < DBL_EPSILON ? 1 : -1];
 }],
 ac_cv_c_long_double=yes, ac_cv_c_long_double=no)
 fi])
 if test $ac_cv_c_long_double = yes; then
   AC_DEFINE(HAVE_LONG_DOUBLE, 1,
-            [Define if the `long double' type works.])
+    [Define if the long double has greater range or precision than double.])
 fi
 ])# AC_C_LONG_DOUBLE
 
--- doc/autoconf.texi   Fri Nov  2 16:10:56 2001
+++ doc/autoconf.texi   Fri Nov 16 16:52:47 2001
@@ -4775,7 +4775,8 @@
 @defmac AC_C_LONG_DOUBLE
 @acindex C_LONG_DOUBLE
 @cvindex HAVE_LONG_DOUBLE
-If the C compiler supports the @code{long double} type, define
+If the C compiler supports a @code{long double} type with greater
+range or precision than the @code{double} type, define
 @code{HAVE_LONG_DOUBLE}.  Some C compilers that do not define
 @code{__STDC__} do support the @code{long double} type; some compilers
 that define @code{__STDC__} do not support @code{long double}.

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