Slight correction on wording:
3-) Introduce a new module specific mechanism for exporting macros from
modules that are preprocessed only once. (Similar to PCH, you create a new
file for macros)

On Tue, Dec 3, 2024 at 9:04 AM James <james.business.84_at_[hidden]> wrote:

> While working with C++ modules, I’ve noticed there’s currently no way to
> export macros from a module. Even if you wanted to opt into this, there’s
> no mechanism available.
>
> Given that macros are still essential for tasks like conditional
> compilation, this feels like a limitation. While macros can be
> controversial, they do help avoid repetitive and error-prone boilerplate in
> certain cases.
>
> Using headers is still an option, but it somewhat defeats the purpose of
> modules since each header needs to be parsed and preprocessed for every
> translation unit. PCHs can help, but they’re limited to a single PCH per
> project and require additional setup.
>
> I’d like to see a solution to this, but I’m unsure of the best path
> forward. Here are a few ideas I’ve considered:
> 1-) Allow exporting macros from modules (perhaps with a special directive
> like "#define_export").
> 2-) Enhance PCHs to be importable from consumed libraries. (meaning
> consumers will have both their own PCH(if there is one) and also consumed
> libraries' PCH precompiled)
> 3-) Introduce a mechanism for exporting macros from modules that are
> preprocessed only once.
>