[cfe-dev] [clang-tidy][RFC] Run each check only once

[Carlos Galvez via cfe-dev]

Hi!

Are there any opinions on this topic? As said, there has been several
commit attempts to fix this, but people thought it would be better to first
discuss it here before hacking some code. So that's why I'm bringing this
up :)

Thanks!
/Carlos

On Mon, Sep 27, 2021 at 1:50 PM Carlos Galvez <carlosgalvezp at gmail.com>
wrote:

> Hi!
>
> I'm writing to this list as suggested in this bug:
> https://reviews.llvm.org/D72566
>
> Background
> =========
>
> clang-tidy has implemented a number of checks, some of which are *aliases* of
> "real" checks. Currently if a user specifies that they want to run both the
> "real" and the "alias" check, clang-tidy will run the same check twice. Or
> N times if there are N aliases.
>
> When applying clang-tidy to large codebases, this can have a severe impact
> in runtime in Continuous Integration checks. The only solution so far is to
> manually disable alias checks, but this generates noise in the config file,
> and is error-prone and cumbersome to maintain in the future, as one always
> need to check the LLVM docs to see what is aliasing what.
>
> I have read in different bugs that one tricky problem with this is that
> "some alias checks run with different defaults, therefore leading to
> different results". I would be interested to know which checks are these
> and where this different default configuration is documented. I would argue
> that if 2 checks run different things and produce different results, then
> they are not aliases. They may share the same implementation, but they are
> not identical (therefore cannot be called "aliases".
>
> I have also read the argument "people should not enable all checks". I
> believe that should be up to users to decide. Plus, as we've seen, there
> are aliases even within the same category, e.g. "cert-*", so the problem
> still remains.
>
> Proposal
> =======
>
> - Find which checks are "fake aliases", if any - share the same
> implementation but run with different defaults and produce different
> results. Change these checks to not be considered as "aliases".
>
> - Add an opt-in feature (command line, config) to enable "the same check
> should be run only once". Diagnostics should come only from the "main"
> check (if it's active) or from the "alias" check (if the "main" check is
> not active).
>
> Let me know what you think! I'm a total newby to LLVM but I'm happy to
> contribute in any way I can :)
>
> Thanks!
> /Carlos
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20211003/be7a9348/attachment-0001.html>