Re: Interest for C++20 modules support of boost officially

From: Chuanqi Xu (chuanqi.xcq_at_[hidden])
Date: 2024-12-20 02:18:23

> Where does the .cppm file go by convention? In which directory?
No convention yet. Some people suggests to `<install-dir>/modules`. Some people suggests `<install-dir>/share`. There are some people suggests `<install-dir>/include` too.
libc++ chose `<install-dir>/share`. And if I read correctly, libstdc++ chose `<install-dir>/include`. So this is more or less a non-consensus topic now.
Thanks,
Chuanqi
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From:Peter Dimov via Boost <boost_at_[hidden]>
Send Time:2024 Dec. 19 (Thu.) 22:43
To:boost<boost_at_[hidden]>
Cc:Peter Dimov<pdimov_at_[hidden]>
Subject:Re: [boost] Interest for C++20 modules support of boost officially
Ruben Perez wrote:
> If I understood the CMake developers and Chuanqi correctly (please let me
> know if I didn't), you do install a library with the generated object files, but
> you do not install the BMIs, as they're like pre-compiled headers.
> 
> Let me explain how I understood it with two concrete examples. Take
> Boost.Url as an example of a compiled library, and Boost.Regex as an example
> of a header-only library.
> 
> 1. Boost.Url today installs:
> * libboost_url.a, containing function definitions.
> * Headers, containing declarations.
> 2. Boost.Url in the module world would install:
> * libboost_url.a, containing the same function definitions as above.
> * A boost_url.cppm file, akin to what headers are today.
> CMake would build a BMI from this file when a user needs to import
> boost.url.
> In practice, this cppm file will likely be implemented in terms of the
> header files that we have today.
Since this .cppm file will include the header files, the header files
should also be installed in the module case.
Where does the .cppm file go by convention? In which directory?
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