Re: C++20 module mapper

[Andrew Jones <andrewvaughanj@gmail.com>]

Hi Alexander,

Actually, I've done some work on this:

      https://github.com/andrewvaughanj/cpp20_module_examples

and more specifically:

      https://github.com/andrewvaughanj/cpp20_module_examples/blob/main/do_gcc.sh

Please take a look and feel free to ask if you have any questions -- cheers,

Andrew

On Tue, Oct 19, 2021 at 4:58 PM Alexander Christensen via Gcc-help
<gcc-help@gcc.gnu.org> wrote:
>
> Hi, I hope I write to the right place.
>
> I would like to know how to use the module mapper, documented here https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Module-Mapper.html,
> to change the location of the expected gcm.cache directory. Given an example project layout:
>
> src/
>     Makefile
>     project_1/
>         // .cpp source files
>         Makefile
>     project_2/
>         // .cpp source files
>         Makefile
>
> Compiling from inside project_1 and project_2 folders does not work with the default module mapper, as gcc expects the module cache
> to be located in current working directory, which is a problem if project_2 references modules built in project_1.
> However, I can specify a module-mapping file. But I can't get it to work.
>
> What would be the correct syntax for such a file, located in project_2, to override the default module cache to read from modules in
> src/gcm.cache/ and NOT src/project_2/gcm.cache/ ? This does not work:
>
> // module_mapping.txt
> '$root' ../gcm.cache/
>
> And I do not want to prepend "cd .. && " to all build commands in src/project_2/Makefile.
>
>
> Sincerely,
> Alexander
>