warn about newfangled vfork() caveats

p4raw-id: //depot/perl@3147

diff --git a/Configure b/Configure
index 45c4761..52d57b2 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -10156,7 +10156,16 @@ $define)
        false) dflt='n';;
        *) dflt='y';;
        esac
-       rp="Some systems have problems with vfork().  Do you want to use it?"
+       cat <<'EOM'
+ 
+Perl can only use a vfork() that doesn't suffer from strict
+restrictions on calling functions or modifying global data in
+the child.  For example, glibc-2.1 contains such a vfork()
+that is unsuitable.  If your system provides a proper fork()
+call, chances are that you do NOT want perl to use vfork().
+
+EOM
+       rp="Do you still want to use vfork()?"
        . ./myread
        case "$ans" in
        y|Y) ;;