Mark de Wever 0756378b77 [libc++][modules] Re-add build dir CMakeLists.txt. (#81370)
This CMakeLists.txt is used to build modules without build system
support. This was removed in d06ae33ec32122bb526fb35025c1f0cf979f1090.
This is used in the documentation how to use modules.

Made some minor changes to make it work with the std.compat module using
the std module.

Note the CMakeLists.txt in the build dir should be removed once build
system support is generally available.

(cherry picked from commit fc0e9c8315564288f9079a633892abadace534cf)
2024-02-16 11:01:06 -08:00
..

The "module partitions" for the std module

The files in this directory contain the exported named declarations per header. These files are used for the following purposes:

  • During testing exported named declarations are tested against the named declarations in the associated header. This excludes reserved names; they are not exported.
  • Generate the module std.

These use cases require including the required headers for these "partitions" at different locations. This means the user of these "partitions" are responsible for including the proper header and validating whether the header can be loaded in the current libc++ configuration. For example "include " fails when locales are not available. The "partitions" use the libc++ feature macros to export the declarations available in the current configuration. This configuration is available if the user includes the `__config' header.

We use .inc files that we include from the top-level module instead of using real C++ module partitions. This is a lot faster than module partitions, see this for details.