Avoid calling the undeclared exit function.  Instead return
from main.  Implicit function declarations were removed from C99,
and future compilers are likely to reject them.

diff --git a/acinclude.m4 b/acinclude.m4
index 7e60b706304f461d..240af3ff04086d74 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -14,7 +14,7 @@ int main (void)
    nan = inf / inf;
    /* nan = 0.0 / 0.0; */
    status = (nan == nan);
-   exit (status);
+   return status;
 }]])],
 [ac_cv_c_ieee_comparisons="yes"],
 [ac_cv_c_ieee_comparisons="no"],
@@ -43,7 +43,7 @@ int main (void)
    double x = 0.0;
    double inf = 1.0 / x;
    int status = (inf < DBL_MAX/2.);
-   exit (status);
+   return status;
 }]])],
 [ac_cv_c_divide_by_zero="yes"],
 [ac_cv_c_divide_by_zero="no"],
diff --git a/configure b/configure
index 08d0feb3b47ddcb8..5f2e4843b26d63ea 100755
--- a/configure
+++ b/configure
@@ -18209,7 +18209,7 @@ int main (void)
    nan = inf / inf;
    /* nan = 0.0 / 0.0; */
    status = (nan == nan);
-   exit (status);
+   return status;
 }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"
@@ -18254,7 +18254,7 @@ int main (void)
    double x = 0.0;
    double inf = 1.0 / x;
    int status = (inf < DBL_MAX/2.);
-   exit (status);
+   return status;
 }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"