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.

2 files changed, 18 insertions, 10 deletions

diff --git a/configure b/configure
index 0fb9504cef7..754da60eaea 100755
--- a/configure
+++ b/configure
@@ -10382,7 +10382,6 @@ 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
@@ -10391,7 +10390,9 @@ else
   cat >conftest.$ac_ext <<_ACEOF
 #line $LINENO "configure"
 #include "confdefs.h"
+
 #include <math.h>
+double glob_double;
 
 #ifdef F77_DUMMY_MAIN
 #  ifdef __cplusplus
@@ -10402,7 +10403,7 @@ else
 int
 main ()
 {
-double x = 0.0; int res = isinf(x);
+return isinf(glob_double) ? 0 : 1;
   ;
   return 0;
 }
@@ -10913,7 +10914,10 @@ echo $ECHO_N "checking for finite... $ECHO_C" >&6
 cat >conftest.$ac_ext <<_ACEOF
 #line $LINENO "configure"
 #include "confdefs.h"
+
 #include <math.h>
+double glob_double;
+
 #ifdef F77_DUMMY_MAIN
 #  ifdef __cplusplus
      extern "C"
@@ -10923,7 +10927,7 @@ cat >conftest.$ac_ext <<_ACEOF
 int
 main ()
 {
-int dummy=finite(1.0);
+return finite(glob_double) ? 0 : 1;
   ;
   return 0;
 }
diff --git a/configure.in b/configure.in
index 117243adac4..0f740d4e330 100644
--- a/configure.in
+++ b/configure.in
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $Header: /cvsroot/pgsql/configure.in,v 1.217.2.21 2006/01/05 03:59:19 momjian Exp $
+dnl $Header: /cvsroot/pgsql/configure.in,v 1.217.2.22 2006/01/12 19:24:47 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -823,12 +823,13 @@ AC_CHECK_FUNCS(vsnprintf, [], pgac_need_repl_snprintf=yes)
 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])])
 
@@ -877,8 +878,11 @@ 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, [Set to 1 if you have finite()])
 AC_MSG_RESULT(yes)],
             [AC_MSG_RESULT(no)])