spurious roundl output (was: computing long double NaN on Irix 6.5)

[Eric Blake]

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According to Bruno Haible on 2/27/2009 6:22 AM:
>> (cached) (cached) checking for signbit macro... no
>> checking for signbit compiler built-ins... no
> 
> This comes from the gl_FUNC_FLOORL_LIBS and gl_FUNC_CEILL_LIBS macros, which 
> are
> invoked by gl_FUNC_ROUNDL. Each of them contains an AC_CACHE_VAL invocation 
> that
> is not wrapped in AC_MSG_CHECKING.
> 
>> Ouch.  That double (cached) at the beginning of a line means that we are
>> doing one AC_CACHE_CHECK inside the body of another, and that it is likely
>> that 'configure -C' will get things wrong on a second run.
> 
> 'configure -C' does not mishandle AC_CACHE_VAL just because there is no 
> AC_MSG_*
> around it?

After further thinking, I don't think we have any situation where
configure gets the wrong answers.  However, the spurious output is still
misleading, so what do you think of this patch to clean it up?  I have not
pushed it yet...

A variable with _cv_ in the name is still cached, regardless of whether
you used AC_CACHE_VAL; all AC_CACHE_VAL does is wrap additional logic to
produce output, thus it should not be used in situations where you don't
want the side effect of output.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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From fff1f75d5b86671f9522fc6952081ed786767076 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Fri, 27 Feb 2009 06:37:17 -0700
Subject: [PATCH] roundl: avoid spurious (cached) output in configure

* m4/floorl.m4 (gl_FUNC_FLOORL_LIBS): Avoid output from
AC_CACHE_VAL if cache value is already set.
* m4/ceill.m4 (gl_FUNC_CEILL_LIBS): Likewise.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog    |    5 +++++
 m4/ceill.m4  |    8 ++++----
 m4/floorl.m4 |    8 ++++----
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9946a0c..fd077e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2009-02-27  Eric Blake  <address@hidden>

+       roundl: avoid spurious (cached) output in configure
+       * m4/floorl.m4 (gl_FUNC_FLOORL_LIBS): Avoid output from
+       AC_CACHE_VAL if cache value is already set.
+       * m4/ceill.m4 (gl_FUNC_CEILL_LIBS): Likewise.
+
        doc: mention more functions added in cygwin 1.7.0
        * doc/posix-functions/mbsnrtowcs.texi: Mention recent cygwin 1.7.0
        addition.
diff --git a/m4/ceill.m4 b/m4/ceill.m4
index 676c64b..eee3837 100644
--- a/m4/ceill.m4
+++ b/m4/ceill.m4
@@ -1,5 +1,5 @@
-# ceill.m4 serial 3
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# ceill.m4 serial 4
+dnl Copyright (C) 2007, 2009 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.
@@ -34,7 +34,7 @@ AC_DEFUN([gl_FUNC_CEILL],
 # Sets CEILL_LIBM.
 AC_DEFUN([gl_FUNC_CEILL_LIBS],
 [
-  AC_CACHE_VAL([gl_cv_func_ceill_libm], [
+  if test "x$gl_cv_func_ceill_libm" = x ; then
     gl_cv_func_ceill_libm=?
     AC_TRY_LINK([
        #ifndef __NO_MATH_INLINES
@@ -57,6 +57,6 @@ AC_DEFUN([gl_FUNC_CEILL_LIBS],
         [gl_cv_func_ceill_libm="-lm"])
       LIBS="$save_LIBS"
     fi
-  ])
+  fi
   CEILL_LIBM="$gl_cv_func_ceill_libm"
 ])
diff --git a/m4/floorl.m4 b/m4/floorl.m4
index 6207811..731451f 100644
--- a/m4/floorl.m4
+++ b/m4/floorl.m4
@@ -1,5 +1,5 @@
-# floorl.m4 serial 3
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# floorl.m4 serial 4
+dnl Copyright (C) 2007, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -34,7 +34,7 @@ AC_DEFUN([gl_FUNC_FLOORL],
 # Sets FLOORL_LIBM.
 AC_DEFUN([gl_FUNC_FLOORL_LIBS],
 [
-  AC_CACHE_VAL([gl_cv_func_floorl_libm], [
+  if test "x$gl_cv_func_floorl_libm" = x ; then
     gl_cv_func_floorl_libm=?
     AC_TRY_LINK([
        #ifndef __NO_MATH_INLINES
@@ -57,6 +57,6 @@ AC_DEFUN([gl_FUNC_FLOORL_LIBS],
         [gl_cv_func_floorl_libm="-lm"])
       LIBS="$save_LIBS"
     fi
-  ])
+  fi
   FLOORL_LIBM="$gl_cv_func_floorl_libm"
 ])
-- 
1.6.1.2