Fix #1966. Try to convince clever compilers not to optimize away the sincos() test...

diff --git a/configure.ac b/configure.ac
index b23df76ff9d99905d9a249d30afee5612072ac6f..07b09c17732e10320f1acd6085d18bc31266c3dd 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -2898,6 +2898,8 @@ AM_CONDITIONAL(WITH_IPSEPCOLA, [test "x$use_ipsepcola" = "xYes"])
 # -----------------------------------
 # Special checks
 
+save_LIBS=$LIBS
+LIBS="$LIBS $MATH_LIBS"
 AC_MSG_CHECKING(if have working sincos())
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
        #include <stdio.h>
@@ -2906,11 +2908,13 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
        extern void sincos(double x, double *s, double *c);
        int main () {
                double sinx=0.0, cosx=1.0;
-               sincos(PI/2.0,&sinx,&cosx);
-               assert(sinx>0.9999999);
-               assert(sinx<1.0000001);
-               assert(cosx<0.0000001);
-               assert(cosx>(-0.0000001));
+                int i;
+                /* try to convince clever compilers not to optize this away! */
+                for (i=2; i<4; i++) {sincos(PI/(double)i,&sinx,&cosx);}
+               assert(sinx>0.8660253);
+               assert(sinx<0.8660255);
+               assert(cosx<0.5000001);
+               assert(cosx>0.4999999);
                return 0;
        }
        ]])],[AC_MSG_RESULT(yes)
@@ -2918,6 +2922,7 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
        ],[AC_MSG_RESULT(no)
        ],[AC_MSG_RESULT(no - assumed because cross-compiling)
        ])
+LIBS=$save_LIBS
 
 # -----------------------------------
 AC_MSG_CHECKING(if FILE struct contains _cnt)