- `-Wmissing-prototypes` and `-Wmissing-variable-declarations` are
helpful for finding dead code and/or things that should be `static`
but aren't marked as such.
- `-Wunused-macros` is of similar utility, but for identifying dead macros.
- `-Wunreachable-code` and `-Wunreachable-code-aggressive` do exactly
what they say: flag unreachable code.
Following from PR #2481, we replace all integer-to-pointer casts [which
hide pointer provenance information (and thus inhibit
optimizations)](https://clang.llvm.org/extra/clang-tidy/checks/performance/no-int-to-ptr.html)
with equivalent operations that preserve this information. I have
enabled the corresponding clang-tidy check in our static analysis CI so
that we do not get bitten by this again in the future.
For the sake of consistency, function definitions and their
corresponding declarations should use the same names for parameters.
I've enabled this check in static analysis to prevent this issue from
occurring again in the future.
Adding `-Wstrict-prototypes` to the default `CFLAGS` in PR #2473 had the
non-obvious side-effect of breaking configure-time feature detection,
because the [test-program `autoconf` generates for feature
detection](https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/Generating-Sources.html#:~:text=main%20())
defines `main` as:
```c
int main()
```
Which causes all feature checks to fail, since this triggers
`-Wstrict-prototypes` and the feature checks use `-Werror`.
Resolved by only adding `-Wstrict-prototypes` to
`EXTRA_{CFLAGS,CXXFLAGS}` in CI, since these flags are not used during
feature detection and we control which compiler is used.
Now that all of the various issues that static analysis uncovered have
been fixed (#2431, #2432, #2433, #2436, #2437, #2446), I've added a
GitHub action which will run static analysis for every PR going forward.
When static analysis detects issues with your code, the GitHub action
provides a link to download its findings in a form tailored for human
consumption.
Take a look at [this demonstration of what it looks like when static
analysis issues are
found](https://github.com/Svetlitski/jemalloc/actions/runs/5010245602)
on my fork for an example (make sure to follow the instructions in the
error message to download and inspect the results).
