+# Only set _FORTIFY_SOURCE when optimizations are enabled. If optimizations
+# are disabled, _FORTIFY_SOURCE doesn't do anything, and causes tons of
+# warnings during compiling on some distributions (at least Fedora).
+AS_CASE([" $CFLAGS "], [*" -O0 "*], [], [AX_APPEND_FLAG(["-D_FORTIFY_SOURCE=2"], [CPPFLAGS])])
+