cmake: enable `-pedantic-errors` for clang when `CURL_WERROR=ON`

clang doesn't have the issues of GCC and old CMake versions.

Note: This introduces asymmetry with autotools, which o

cmake: enable `-pedantic-errors` for clang when `CURL_WERROR=ON`

clang doesn't have the issues of GCC and old CMake versions.

Note: This introduces asymmetry with autotools, which only enables
this for GCC.

Reviewed-by: Daniel Stenberg
Closes #13286

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cmake: fix `CURL_WERROR=ON` for old CMake and use it in GHA/linux-old

- cmake: fix `-pedantic-errors` for old CMake with `CURL_WERROR=ON` set.

`-pedantic-errors` option throws a w

cmake: fix `CURL_WERROR=ON` for old CMake and use it in GHA/linux-old

- cmake: fix `-pedantic-errors` for old CMake with `CURL_WERROR=ON` set.

`-pedantic-errors` option throws a warning with GCC (all versions) and
makes `check_symbol_exists()` fail in CMake versions older than
v3.23.0 (2022-03-29), when CMake introduced a workaround:

https://gitlab.kitware.com/cmake/cmake/-/issues/13208
https://gitlab.kitware.com/cmake/cmake/-/commit/eeb45401163d831b8c841ef6eba81466b4067b68
https://gitlab.kitware.com/cmake/cmake/-/commit/1ab7c3cd28b27ca162c4559e1026e5cad1898ade

Follow-up to 3829759bd042c03225ae862062560f568ba1a231 #12489

- set `CURL_WERROR=ON` for the `linux-old` job in CI.

Closes #13282

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build: fix some `-Wsign-conversion`/`-Warith-conversion` warnings

- enable `-Wsign-conversion` warnings, but also setting them to not
raise errors.
- fix `-Warith-conversion` warni

build: fix some `-Wsign-conversion`/`-Warith-conversion` warnings

- enable `-Wsign-conversion` warnings, but also setting them to not
raise errors.
- fix `-Warith-conversion` warnings seen in CI.
These are triggered by `-Wsign-converion` and causing errors unless
explicitly silenced. It makes more sense to fix them, there just a few
of them.
- fix some `-Wsign-conversion` warnings.
- hide `-Wsign-conversion` warnings with a `#pragma`.
- add macro `CURL_WARN_SIGN_CONVERSION` to unhide them on a per-build
basis.
- update a CI job to unhide them with the above macro:
https://github.com/curl/curl/actions/workflows/linux.yml -> OpenSSL -O3

Closes #12492

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build: enable missing OpenSSF-recommended warnings, with fixes

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
as of 2023-11-29 [1]

build: enable missing OpenSSF-recommended warnings, with fixes

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
as of 2023-11-29 [1].

Enable new recommended warnings (except `-Wsign-conversion`):

- enable `-Wformat=2` for clang (in both cmake and autotools).
- add `CURL_PRINTF()` internal attribute and mark functions accepting
printf arguments with it. This is a copy of existing
`CURL_TEMP_PRINTF()` but using `__printf__` to make it compatible
with redefinting the `printf` symbol:
https://gcc.gnu.org/onlinedocs/gcc-3.0.4/gcc_5.html#SEC94
- fix `CURL_PRINTF()` and existing `CURL_TEMP_PRINTF()` for
mingw-w64 and enable it on this platform.
- enable `-Wimplicit-fallthrough`.
- enable `-Wtrampolines`.
- add `-Wsign-conversion` commented with a FIXME.
- cmake: enable `-pedantic-errors` the way we do it with autotools.
Follow-up to d5c0351055d5709da8f3e16c91348092fdb481aa #2747
- lib/curl_trc.h: use `CURL_FORMAT()`, this also fixes it to enable format
checks. Previously it was always disabled due to the internal `printf`
macro.

Fix them:

- fix bug where an `set_ipv6_v6only()` call was missed in builds with
`--disable-verbose` / `CURL_DISABLE_VERBOSE_STRINGS=ON`.
- add internal `FALLTHROUGH()` macro.
- replace obsolete fall-through comments with `FALLTHROUGH()`.
- fix fallthrough markups: Delete redundant ones (showing up as
warnings in most cases). Add missing ones. Fix indentation.
- silence `-Wformat-nonliteral` warnings with llvm/clang.
- fix one `-Wformat-nonliteral` warning.
- fix new `-Wformat` and `-Wformat-security` warnings.
- fix `CURL_FORMAT_SOCKET_T` value for mingw-w64. Also move its
definition to `lib/curl_setup.h` allowing use in `tests/server`.
- lib: fix two wrongly passed string arguments in log outputs.
Co-authored-by: Jay Satiro
- fix new `-Wformat` warnings on mingw-w64.

[1] https://github.com/ossf/wg-best-practices-os-developers/blob/56c0fde3895bfc55c8a973ef49a2572c507b2ae1/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C%2B%2B.md

Closes #12489

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build: add more picky warnings and fix them

Enable more picky compiler warnings. I've found these options in the
nghttp3 project when implementing the CMake quick picky warning
funct

build: add more picky warnings and fix them

Enable more picky compiler warnings. I've found these options in the
nghttp3 project when implementing the CMake quick picky warning
functionality for it [1].

`-Wunused-macros` was too noisy to keep around, but fixed a few issues
it revealed while testing.

- autotools: reflect the more precisely-versioned clang warnings.
Follow-up to 033f8e2a08eb1d3102f08c4d8c8e85470f8b460e #12324
- autotools: sync between clang and gcc the way we set `no-multichar`.
- autotools: avoid setting `-Wstrict-aliasing=3` twice.
- autotools: disable `-Wmissing-noreturn` for MSYS gcc targets [2].
It triggers in libtool-generated stub code.

- lib/timeval: delete a redundant `!MSDOS` guard from a `WIN32` branch.

- lib/curl_setup.h: delete duplicate declaration for `fileno`.
Added in initial commit ae1912cb0d494b48d514d937826c9fe83ec96c4d
(1999-12-29). This suggests this may not be needed anymore, but if
it does, we may restore this for those specific (non-Windows) systems.
- lib: delete unused macro `FTP_BUFFER_ALLOCSIZE` since
c1d6fe2aaa5a26e49a69a4f2495b3cc7a24d9394.
- lib: delete unused macro `isxdigit_ascii` since
f65f750742068f579f4ee6d8539ed9d5f0afcb85.
- lib/mqtt: delete unused macro `MQTT_HEADER_LEN`.
- lib/multi: delete unused macro `SH_READ`/`SH_WRITE`.
- lib/hostip: add `noreturn` function attribute via new `CURL_NORETURN`
macro.
- lib/mprintf: delete duplicate declaration for `Curl_dyn_vprintf`.
- lib/rand: fix `-Wunreachable-code` and related fallouts [3].
- lib/setopt: fix `-Wunreachable-code-break`.
- lib/system_win32 and lib/timeval: fix double declarations for
`Curl_freq` and `Curl_isVistaOrGreater` in CMake UNITY mode [4].
- lib/warnless: fix double declarations in CMake UNITY mode [5].
This was due to force-disabling the header guard of `warnless.h` to
to reapply it to source code coming after `warnless.c` in UNITY
builds. This reapplied declarations too, causing the warnings.
Solved by adding a header guard for the lines that actually need
to be reapplied.
- lib/vauth/digest: fix `-Wunreachable-code-break` [6].
- lib/vssh/libssh2: fix `-Wunreachable-code-break` and delete redundant
block.
- lib/vtls/sectransp: fix `-Wunreachable-code-break` [7].
- lib/vtls/sectransp: suppress `-Wunreachable-code`.
Detected in `else` branches of dynamic feature checks, with results
known at compile-time, e.g.
```c
if(SecCertificateCopySubjectSummary) /* -> true */
```
Likely fixable as a separate micro-project, but given SecureTransport
is deprecated anyway, let's just silence these locally.
- src/tool_help: delete duplicate declaration for `helptext`.
- src/tool_xattr: fix `-Wunreachable-code`.
- tests: delete duplicate declaration for `unitfail` [8].
- tests: delete duplicate declaration for `strncasecompare`.
- tests/libtest: delete duplicate declaration for `gethostname`.
Originally added in 687df5c8c39c370a59999b9afc0917d808d978b7
(2010-08-02).
Got complicated later: c49e9683b85ba9d12cbb6eebc4ab2c8dba68fbdc
If there are still systems around with warnings, we may restore the
prototype, but limited for those systems.
- tests/lib2305: delete duplicate declaration for
`libtest_debug_config`.
- tests/h2-download: fix `-Wunreachable-code-break`.

[1] https://github.com/ngtcp2/nghttp3/blob/a70edb08e954d690e8fb2c1df999b5a056f8bf9f/cmake/PickyWarningsC.cmake
[2] https://ci.appveyor.com/project/curlorg/curl/builds/48553586/job/3qkgjauiqla5fj45?fullLog=true#L1675
[3] https://github.com/curl/curl/actions/runs/6880886309/job/18716044703?pr=12331#step:7:72
https://github.com/curl/curl/actions/runs/6883016087/job/18722707368?pr=12331#step:7:109
[4] https://ci.appveyor.com/project/curlorg/curl/builds/48555101/job/9g15qkrriklpf1ut#L204
[5] https://ci.appveyor.com/project/curlorg/curl/builds/48555101/job/9g15qkrriklpf1ut#L218
[6] https://github.com/curl/curl/actions/runs/6880886309/job/18716042927?pr=12331#step:7:290
[7] https://github.com/curl/curl/actions/runs/6891484996/job/18746659406?pr=12331#step:9:1193
[8] https://github.com/curl/curl/actions/runs/6882803986/job/18722082562?pr=12331#step:33:1870

Closes #12331

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build: picky warning updates

- cmake: sync some picky gcc warnings with autotools.
- cmake, autotools: add `-Wold-style-definition` for clang too.
- cmake: more precise version info

build: picky warning updates

- cmake: sync some picky gcc warnings with autotools.
- cmake, autotools: add `-Wold-style-definition` for clang too.
- cmake: more precise version info for old clang options.
- cmake: use `IN LISTS` syntax in `foreach()`.

Reviewed-by: Daniel Stenberg
Reviewed-by: Marcel Raad
Closes #12324

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cmake: speed up and extend picky clang/gcc options

Extend existing picky compiler options with ones missing compared to
autotools builds. Also sync options between clang and gcc.

cmake: speed up and extend picky clang/gcc options

Extend existing picky compiler options with ones missing compared to
autotools builds. Also sync options between clang and gcc.

Redesign the way we enable these options to avoid the slow option
detection almost completely.

This reduces the number of detections from 35 to zero for clang and
3 for gcc, even after adding a bunch of new options.

clang 3.0 (2011-11-29) and gcc 2.95 (1999-07-31) now required.

Also show enabled picky options.

Ref: https://github.com/libssh2/libssh2/pull/952

Reviewed-by: Daniel Stenberg
Closes #10973

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