Currently, the library-internal feature test macros are only defined if
the feature is not available, and always have the prefix
`_LIBCPP_HAS_NO_`. This patch changes that, so that they are always
defined and have the prefix `_LIBCPP_HAS_` instead. This changes the
canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means
that using an undefined macro (e.g. due to a missing include) is
diagnosed now. While this is rather unlikely currently, a similar change
in `<__configuration/availability.h>` caught a few bugs. This also
improves readability, since it removes the double-negation of `#ifndef
_LIBCPP_HAS_NO_FEATURE`.
The current patch only touches the macros defined in `<__config>`. If
people are happy with this approach, I'll make a follow-up PR to also
change the macros defined in `<__config_site>`.
This attribute is used in the headers. Not using this in the modules has
led to several issues. Add them to the modules to avoid these errors in
other placed.
This is missing e.g. on Windows. With this change, it's possible to make
the libcxx std module work on mingw-w64 (although that requires a few
fixes to those headers).
In the regular cstdlib header, we have _LIBCPP_USING_IF_EXISTS flagged
on every single reexported function (since
a9c9183ca42629fa83cdda297d1d30c7bc1d7c91), but the modules seem to only
have _LIBCPP_USING_IF_EXISTS set on a few individual functions, so far.
libc on macOS does not provide at_quick_exit or quick_exit. This allows
modules to build on macOS and defer any errors to usage site of these
symbols.
Fixes: https://github.com/llvm/llvm-project/issues/77559
This adds the std.compat module. The patch contains a bit of refactoring
to avoid code duplication between the std and std.compat module.
Implements parts of
- P2465R3 Standard Library Modules std and std.compat
