-# 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])])
+ # Cannot use AX_APPEND_FLAG here, as it assumes no space inside the added flags.
+ # Cannot append flags with AX_APPEND_FLAG one by one, as this would destroy all fortifications
+ # if CPPFLAGS already contain -D_FORTIFY_SOURCE=2.