Use a more bulletproof test for whether finite() and isinf() are present.

It seems that recent gcc versions can optimize away calls to these functions
even when the functions do not exist on the platform, resulting in a bogus
positive result.  Avoid this by using a non-constant argument and ensuring
that the function result is not simply discarded.  Per report from
François Laupretre.

diff --git a/configure b/configure
index 60270b638d234a259e2126c2079b199020742c8c..52a1605cffed7626508a00dee17210bbae491832 100755 (executable)
--- a/configure
+++ b/configure
@@ -14241,7 +14241,6 @@ fi
 
 
 
-# do this one the hard way in case isinf() is a macro
 echo "$as_me:$LINENO: checking for isinf" >&5
 echo $ECHO_N "checking for isinf... $ECHO_C" >&6
 if test "${ac_cv_func_isinf+set}" = set; then
@@ -14253,12 +14252,14 @@ _ACEOF
 cat confdefs.h >>conftest.$ac_ext
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
+
 #include <math.h>
+double glob_double;
 
 int
 main ()
 {
-double x = 0.0; int res = isinf(x);
+return isinf(glob_double) ? 0 : 1;
   ;
   return 0;
 }
@@ -15138,11 +15139,14 @@ _ACEOF
 cat confdefs.h >>conftest.$ac_ext
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
+
 #include <math.h>
+double glob_double;
+
 int
 main ()
 {
-int dummy=finite(1.0);
+return finite(glob_double) ? 0 : 1;
   ;
   return 0;
 }

diff --git a/configure.in b/configure.in
index c57e93282adb308d0aae8593c46d8cf86f1566b4..572f9d2265d90e13722141558a2c6dc13ebd25e5 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.431.2.5 2006/01/05 04:02:23 momjian Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.431.2.6 2006/01/12 19:23:41 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -892,12 +892,13 @@ fi
 AC_CHECK_DECLS([snprintf, vsnprintf])
 
 
-# do this one the hard way in case isinf() is a macro
+dnl Cannot use AC_CHECK_FUNC because isinf may be a macro
 AC_CACHE_CHECK([for isinf], ac_cv_func_isinf,
-[AC_TRY_LINK(
-[#include <math.h>
+[AC_TRY_LINK([
+#include <math.h>
+double glob_double;
 ],
-[double x = 0.0; int res = isinf(x);],
+[return isinf(glob_double) ? 0 : 1;],
 [ac_cv_func_isinf=yes],
 [ac_cv_func_isinf=no])])
 
@@ -960,8 +961,11 @@ fi
 
 dnl Cannot use AC_CHECK_FUNC because finite may be a macro
 AC_MSG_CHECKING(for finite)
-AC_TRY_LINK([#include <math.h>],
-            [int dummy=finite(1.0);],
+AC_TRY_LINK([
+#include <math.h>
+double glob_double;
+],
+            [return finite(glob_double) ? 0 : 1;],
             [AC_DEFINE(HAVE_FINITE, 1, [Define to 1 if you have finite().])
 AC_MSG_RESULT(yes)],
             [AC_MSG_RESULT(no)])