On Wed, Dec 20, 2023 at 03:22:17PM +0000, Iain Sandoe wrote:
> Hi Folks,
>
> > On 19 Dec 2023, at 19:55, Mark de Wever via SG15 <sg15_at_[hidden]> wrote:
> >
> > On Tue, Dec 12, 2023 at 04:56:32PM -0500, Daniel Ruoso via SG15 wrote:
> >> As discussed in the meeting on 2023-12-12, I'm putting together a proposal
> >> for the metadata format to be used both when discovering the std modules as
> >> well as for pre-built libraries in general.
> >
> > Based on this proposal I've created a libc++ PR [1]. I got a lot of
> > pushback regarding installing modules in a directory parallel to
> > include. I've changed that directory. The current tentative location is
> >
> > <prefix>/usr/share/libc++/v1/
>
> My recollection is that (amongst other things) the SG15 discussion identified that
> the manifest/module recipe is more tied to the library binary than the headers.
> For example, (at least for libc++) one set of headers might be designed to cater for
> multiple ISAs or incompatible ABIs; nevertheless, those must be distinct in the
> actual library binar(ies) [either as ABI slices, or as separate entities].
>
> Manifests/module information files therefore might need to be identified on the
> basis of user’s compile flags that determine one of a set of incompatible ABI
> slices.
>
> What is your plan for dealing with this in the proposed install?

I have a patch for Clang with a new `-print` option. Unfortunately Clang
`-print` options don't look at the `-stdlib` argument. Currently the
`-print` options show the same include path for libc++ and libstdc++.

This means the libc++ manifest is in the library directory of stdlibc++.
The plan is to fix that. The intention is that

  clang -stdlib=libc++ -print-libray-module-manifest-path

gives

  /path/to/libc++_library/libc++.module.json

As Louis mentioned in the meeting there are plans to ship versions of
libc++ with sanitizers enabled. Then something along the lines of

  clang -stdlib=libc++-asan -print-libray-module-manifest-path

would give

  /path/to/libc++_library/libc++-asan.module.json

Mark