https://bugs.gentoo.org/898410
https://savannah.gnu.org/bugs/?63679

Avoid calling the undeclared exit function and future failures
with compilers which do not support implicit function declarations.

--- a/configure.ac
+++ b/configure.ac
@@ -449,7 +449,7 @@ int main (void)
    inf = exp(1.0e10);
    nan = inf / inf ;
    status = (nan == nan);
-   exit (status);
+   return status;
 }]])],[ac_cv_c_ieee_comparisons="yes"],[ac_cv_c_ieee_comparisons="no"],[ac_cv_c_ieee_comparisons="yes"])
 ])
 
@@ -469,7 +469,7 @@ int main (void)
    for (i = 0; i < 5; i++) { z = z / 10.0 ; };        
    for (i = 0; i < 5; i++) { z = z * 10.0 ; };
    status = (z == 0.0);
-   exit (status);
+   return status;
 }]])],[ac_cv_c_ieee_denormals="yes"],[ac_cv_c_ieee_denormals="no"],[ac_cv_c_ieee_denormals="yes"])
 ])