On Fri, Dec 22, 2023 at 9:13 AM Steve Downey via SG15 <sg15_at_[hidden]>
wrote:

> Marking external headers with -isystem is a common strategy for dealing
> with warning suppression for files outside your control. This can be a
> mistake as it can suppress warnings from misuse such as conversion in std::
> optional, but such are the tradeoffs for false positives.
> If module interfaces are built as part of a project do we need mechanisms
> to suppress warnings? Standard libraries use pragmas to mark themselves,
> but most libraries will and should not?
>
> Thoughts raised due to
> https://lucisqr.substack.com/p/the-warnings-you-never-saw -- which I have
> issues with and have not completely verified.
>

Clang already has `-fsystem-module` for Clang modules. Although with C++20
named modules being separate TUs you might not need it, the build system
can just pass `-Wnone`. Although there are some warnings that are emitted
even in system headers/modules.

Being a system module does have a few other semantics in Clang, but I don't
think any of them would apply to C++20 named modules.

- Michael Spencer