: add -D_FORTIFY_SOURCE if feasible and not already there
case "$gccversion" in
-[4567].*) case "$optimize$ccflags" in
+[456789].*) case "$optimize$ccflags" in
*-O*) case "$ccflags$cppsymbols" in
*_FORTIFY_SOURCE=*) # Don't add it again.
echo "You seem to have -D_FORTIFY_SOURCE already, not adding it." >&4