Warning Discipline and Hardening Flags

The baseline set

• -Wall -Wextra — the standard radar: uninitialized use, sign compare, unused results, missing returns.
• -Werror — warnings become build failures; a warning backlog cannot accumulate.
• -Wpedantic — refuses non-standard constructs, guarding portability claims.
• -Wshadow — a local shadowing an outer name is a read-the-wrong-variable bug waiting.
• -Wconversion — implicit narrowing (int to char, size_t to int) made visible.

Each flag is a class of defect, not a style opinion. This course's own challenges compile under -Wall -Wextra -Wpedantic — the code you write here passes a strict baseline by construction.

Hardening for the runtime

• -D_FORTIFY_SOURCE — the library checks buffer sizes where it can prove them.
• -fstack-protector-strong — canaries before return addresses on frames with arrays.
• Position-independent flags plus ASLR (module 24) make memory-corruption exploits substantially harder.

Hardening flags are not a substitute for correct code; they are the safety net that turns latent corruption into loud aborts during testing.