And -Wextra. Adds some more useful warnings not enabled by -Wall. Even adding -Wextra doesn't turn on everything, yet more have to be turned on manually, like -

And -Wextra. Adds some more useful warnings not enabled by -Wall. Even adding -Wextra doesn't turn on everything, yet more have to be turned on manually, like -Wzero-as-null-pointer-constant.