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

tglsfdc · tglsfdc · commit db0558c11347 · 2006-01-12T19:23:22.000Z
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
@@ -14202,7 +14202,6 @@ 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
@@ -14214,12 +14213,14 @@ _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;
 }
@@ -15102,11 +15103,14 @@ _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
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.441 2006/01/05 03:01:32 momjian Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.442 2006/01/12 19:23:22 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])])
 
@@ -963,8 +964,11 @@ 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)])

Original file line number	Diff line number	Diff line change
`@@ -14202,7 +14202,6 @@ fi`
`14202`	`14202`
`14203`	`14203`
`14204`	`14204`
`14205`		`-# do this one the hard way in case isinf() is a macro`
`14206`	`14205`	`echo "$as_me:$LINENO: checking for isinf" >&5`
`14207`	`14206`	`echo $ECHO_N "checking for isinf... $ECHO_C" >&6`
`14208`	`14207`	`if test "${ac_cv_func_isinf+set}" = set; then`
`@@ -14214,12 +14213,14 @@ _ACEOF`
`14214`	`14213`	`cat confdefs.h >>conftest.$ac_ext`
`14215`	`14214`	`cat >>conftest.$ac_ext <<_ACEOF`
`14216`	`14215`	`/* end confdefs.h. */`
	`14216`	`+`
`14217`	`14217`	`#include <math.h>`
	`14218`	`+double glob_double;`
`14218`	`14219`
`14219`	`14220`	`int`
`14220`	`14221`	`main ()`
`14221`	`14222`	`{`
`14222`		`-double x = 0.0; int res = isinf(x);`
	`14223`	`+return isinf(glob_double) ? 0 : 1;`
`14223`	`14224`	`;`
`14224`	`14225`	`return 0;`
`14225`	`14226`	`}`
`@@ -15102,11 +15103,14 @@ _ACEOF`
`15102`	`15103`	`cat confdefs.h >>conftest.$ac_ext`
`15103`	`15104`	`cat >>conftest.$ac_ext <<_ACEOF`
`15104`	`15105`	`/* end confdefs.h. */`
	`15106`	`+`
`15105`	`15107`	`#include <math.h>`
	`15108`	`+double glob_double;`
	`15109`	`+`
`15106`	`15110`	`int`
`15107`	`15111`	`main ()`
`15108`	`15112`	`{`
`15109`		`-int dummy=finite(1.0);`
	`15113`	`+return finite(glob_double) ? 0 : 1;`
`15110`	`15114`	`;`
`15111`	`15115`	`return 0;`
`15112`	`15116`	`}`