[PATCH v8 0/4] P1689R5 support

[Jason Merrill]

On 9/1/23 09:04, Ben Boeckel wrote:
> Hi,
> 
> This patch series adds initial support for ISO C++'s [P1689R5][], a
> format for describing C++ module requirements and provisions based on
> the source code. This is required because compiling C++ with modules is
> not embarrassingly parallel and need to be ordered to ensure that
> `import some_module;` can be satisfied in time by making sure that any
> TU with `export import some_module;` is compiled first.
> 
> [P1689R5]: https://isocpp.org/files/papers/P1689R5.html
> 
> I've also added patches to include imported module CMI files and the
> module mapper file as dependencies of the compilation. I briefly looked
> into adding dependencies on response files as well, but that appeared to
> need some code contortions to have a `class mkdeps` available before
> parsing the command line or to keep the information around until one was
> made.
> 
> I'd like feedback on the approach taken here with respect to the
> user-visible flags. I'll also note that header units are not supported
> at this time because the current `-E` behavior with respect to `import
> <some_header>;` is to search for an appropriate `.gcm` file which is not
> something such a "scan" can support. A new mode will likely need to be
> created (e.g., replacing `-E` with `-fc++-module-scanning` or something)
> where headers are looked up "normally" and processed only as much as
> scanning requires.
> 
> FWIW, Clang as taken an alternate approach with its `clang-scan-deps`
> tool rather than using the compiler directly.
> 
> Thanks,
> 
> --Ben
> 
> ---
> v7 -> v8:
> 
> - rename `DEPS_FMT_` enum variants to `FDEPS_FMT_` to match the
>    associated flag
> - memory leak fix in the `join` specfunc implementation (also better
>    comments), both from Jason
> - formatting fix in `mkdeps.cc` for `write_make_modules_deps` assignment
> - comments on new functions for P1689R5 implementation

Pushed, thanks!

Jason