Ref:
https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
(2023-11-29)
Enable new warnings:
- replace `-Wno-sign-conversion` with `-Wsign-conversion`.
Fix them in example, tests and wincng. There remain about 360 of these
warnings in `src`. Add a TODO item for those and disable `-Werror` for
this particular warning.
- enable `-Wformat=2` for clang (in both cmake and autotools).
- enable `__attribute__((format))` for `_libssh2_debug()`,
`_libssh2_snprintf()` and in tests for `run_command()`.
`LIBSSH2_PRINTF()` copied from `CURL_TEMP_PRINTF()` in curl.
- enable `-Wimplicit-fallthrough`.
- enable `-Wtrampolines`.
Fix them:
- src: replace obsolete fall-through-comments with
`__attribute__((fallthrough))`.
- wincng: fix `-Wsign-conversion` warnings.
- tests: fix `-Wsign-conversion` warnings.
- example: fix `-Wsign-conversion` warnings.
- src: fix `-Wformat` issues in trace calls.
Also, where necessary fix `int` and `unsigned char` casts to
`unsigned int` and adjust printf format strings. These were not
causing compiler warnings.
Cast large types to `long` to avoid dealing with printf masks for
`size_t` and other C99 types. Existing code often used `int` for this.
I'll update them to `long` in an upcoming commit.
- tests: fix `-Wformat` warning.
- silence `-Wformat-nonliteral` warnings.
- mbedtls: silence `-Wsign-conversion`/`-Warith-conversion`
in external header.
Closes#1257
- os400: delete unused `HAVE_STDINT_H`.
- fuzz: delete redundant `stdint.h` use.
`inttypes.h` is already included via `testinput.h`.
- docs/TODO: adjust type in planned function.
Closes#1212
