[cfe-dev] [clang][RFC] -Wmissing-prototypes: make suggested fix more generic?

[Aaron Ballman via cfe-dev]

On Fri, Dec 10, 2021 at 8:25 AM Carlos Galvez via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
>
> Hi,
>
> We want to enable the warning -Wmissing-prototypes to enforce internal linkage as much as possible. It works great, with one caveat - it suggests to use "static". Internal linkage can also be achieved with anonymous namespaces and Clang will not issue a warning.
>
> Now, the question as to what to use (static vs anonymous namespaces) is mostly a style issue (a "Microscopic Detail" in the LLVM Coding Guidelines). At our company we have decided to prefer anonymous namespaces over static, so we wouldn't want Clang to start suggesting people (especially junior devs that trust the tools blindly) to use static.
>
> Therefore I wanted to ask here - would it be possible to make the suggestion more generic, maybe displaying both alternatives? Best would be making this user-configurable but I'm guessing that's not a trivial thing to do.
>
> I'm happy to implement the changes given some pointers, but I want to check here first if you'd agree with it.

There are a couple of things to keep in mind.

The current fix-it is valid in both C and C++, but anonymous
namespaces are C++ only and so that suggestion would be inappropriate
to make in C.
Multiple fixits means the fix cannot be automatically applied by an
engine, whereas the current behavior can.
Clang does not have a way to configure diagnostic options aside from
the command line. I don't think it would be worth the effort to
support something like `-Wmissing-prototypes=prefer-static` or
something like that to parameterize this diagnostic.

I don't think any of these are necessarily a show-stopper for the
proposed functionality, but they're worth keeping in mind. However,
for me personally, I think the current functionality is sufficient (it
works in all language modes, it's automatable as a fix-it, etc) and
that a perhaps another solution for your situation might be a
clang-tidy check to enforce your company's coding guidelines (which
should hopefully integrate nicely into a CI pipeline for you, can also
automatically apply fix-its, can be tailored to your specific needs,
etc).

~Aaron

>
> Thanks!
> /Carlos
>
>
>
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