Also enable `bugprone-suspicious-realloc-usage` clang-tidy option
to verify.
Fixing:
```
tests/server/rtspd.c:328:37: error: 'req->rtp_buffer' may be set to null if 'realloc' fails,
which may result in a leak of the original buffer
[bugprone-suspicious-realloc-usage,-warnings-as-errors]
328 | req->rtp_buffer = realloc(req->rtp_buffer,
| ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
```
Ref: https://clang.llvm.org/extra/clang-tidy/checks/bugprone/suspicious-realloc-usage.htmlCloses#20621
Fix bigger and smaller kinks in how clang-tidy is configured and used.
Sync behavior more between autotools and cmake, lib/src and tests. Bump
clang-tidy minimum version and prepare logic to allow using clang-tidy
to a fuller extent.
- move clang-tidy settings from builds to a new `.clang-tidy.yml`.
To make it easy to see and edit checks at one place. Also to allow
using the `--checks=` option internally to silence tests-specific
checks. (clang-tidy does not support multiple `--check=` options via
the command-line.)
Use explicit `--config-file=` option to point to the configuration.
- .clang-tidy.yml: link to documentation.
- suppress `clang-diagnostic-nullability-extension` due to a false
positive in libtests with `CURL_WERROR=ON` and `PICKY_COMPILER=OFF`.
- .clang-tidy.yml: enable `portability-*`, `misc-const-correctness`.
- drop `--quiet` clang-tidy option by default to make its working a bit
more transparent. The extra output is minimial.
- consistently use double-dashes in clang-tidy command-line options.
Supported by clang-tidy 9.0.0+ (2019-09-19). Before this patch single
and double were used arbitrarily.
- src/tool_parsecfg: silence false positive `clang-analyzer-unix.Stream`.
Seen with clang 18 + clang-tidy 19 and 20 (only with autotools.)
- INTERNALS: require clang-tidy 14.0.0+. For the `--config-file` option.
- INTERNALS: recommend clang-tidy 19.1.0+, to avoid bogus
`clang-analyzer-valist.Uninitialized` warnings. (bug details below)
autotools:
- allow configuring the clang-tidy tool via `CLANG_TIDY` env.
Also to use in GHA to point to a suffixed clang-tody tool.
- fix to pass CFLAGS to lib, src sources.
(keep omitting them when using a non-clang compiler.)
- fix to pass `--warnings-as-errors=*` in quotes to avoid globbing.
cmake:
- fix to not pass an empty `-I` to clang-tidy.
- fix to pass CFLAGS (picky warnings) to clang-tidy for test sources.
(keep omitting them when using a non-clang compiler.)
- fix to disable `clang-diagnostic-unused-function` for test sources.
(tests have static entry points, which trigger this check when
checking them as individidual sources.)
- fix forwarding `CURL_CLANG_TIDYFLAGS` to clang-tidy.
- force disable picky warnings when running clang-tidy with a non-clang
compiler. To not pass these flags when checking lib and src.
CI:
- GHA/linux: avoid clang-tidy bug by upgrading to v19, and drop the
workaround.
- GHA/linux: switch to clang from gcc in the clang-tidy job. Using gcc
doesn't allow passing CFLAGS to clang-tidy, making it less effective.
(My guess this was one factor contributing to this job often missing
to find certain issues compared to GHA/macos.)
I recomment using clang-tidy with a clang compiler, preferably the same
version or one that's compatible. Other cases are best effort, and may
fail if a C flag is passed to clang-tidy that it does not understand.
Picky warnings are mostly omitted when using a non-clang compiler,
reducing its usefulness.
Details and reproducer for the v18 (and earlier) clang-tidy bug,
previously affecting the GHA/linux job:
clang-tidy <=18 emits false warnings way when passing multiple C sources
at once (as done with autotools):
```sh
cat > src1.c <<EOF
#include <string.h>
static void dummy(void *p) { memcmp(p, p, 0); }
EOF
cat > src2.c <<EOF
#include <stdarg.h>
void vafunc(int option, ...)
{
va_list param;
va_start(param, option);
if(option)
(void)va_arg(param, int);
va_end(param);
}
EOF
/opt/homebrew/opt/llvm@18/bin/clang-tidy --checks=clang-analyzer-valist.Uninitialized src1.c src2.c
# src2.c:7:11: warning: va_arg() is called on an uninitialized va_list [clang-analyzer-valist.Uninitialized]
```
Follow-up to e86542038d#17047Closes#20605
