[libcxx] Add support for SerenityOS

[ADKaster]

Summary

This commit teaches libc++ about what features are available in our
LibC, namely:

• We do not have locale support, so no-op shims should be used in place of the C locale API.
• The number of errno constants defined by us is given by the value of the ELAST macro.
• Multithreading is implemented though the pthread library.
• Use libc++'s builtin character type table instead of the one provided by LibC as there's a lot of extra porting work to convince the rest of locale.cpp to use our character type table properly.

Depends on D154403

[ldionne]

Thanks for the patch! As part of this patch, I would like to also add a CI job that runs the test suite on SerenityOS. You can follow the steps at https://libcxx.llvm.org/AddingNewCIJobs.html#addingnewcijobs. Otherwise, we are not testing any of this new code.

We could also update libcxx/doc/index.rst to add SerenityOS to the list of supported "platforms".

[ldionne]

Gentle ping on this. As part of the Github PR transition, we are clearing the review libc++ review queue. If this isn't updated, we'll close this and it can be re-open as a Github PR instead.

Note that we do want to support SerenityOS given that the changes are really simple and reasonable -- but we need a tester like we do for all our other platforms.

[ADKaster]

Thanks for the ping! Last I checked @BertalanD had a few WIP changes to the Driver patches as requested my MaskRay. I suspect resubmitting this series in GitHub will be the way go though.

[ldionne]

Sounds good, thanks. In that case can you please abandon this to clear our review queue?

[ADKaster]

We will resubmit this patch on GitHub when the rest of the commit stack is ready (and a plan for CI runners is ironed out :) )

libcxx/include/CMakeLists.txt

set(files
   __support/fuchsia/xlocale.h
   __support/ibm/gettod_zos.h
   __support/ibm/locale_mgmt_zos.h
   __support/ibm/nanosleep.h
   __support/ibm/xlocale.h
   __support/musl/xlocale.h
   __support/newlib/xlocale.h
   __support/openbsd/xlocale.h
+  __support/serenity/xlocale.h
   __support/win32/locale_win32.h
   __support/xlocale/__nop_locale_mgmt.h
   __support/xlocale/__posix_l_fallback.h
   __support/xlocale/__strtonum_fallback.h
   __system_error/errc.h
   __system_error/error_category.h
   __system_error/error_code.h
   __system_error/error_condition.h

libcxx/include/__config

#    if defined(__FreeBSD__) ||                                                                                        \
         defined(__NetBSD__) ||                                                                                         \
         defined(__OpenBSD__) ||                                                                                        \
         defined(__NuttX__) ||                                                                                          \
         defined(__linux__) ||                                                                                          \
         defined(__GNU__) ||                                                                                            \
         defined(__APPLE__) ||                                                                                          \
         defined(__MVS__) ||                                                                                            \
         defined(_AIX) ||                                                                                               \
-        defined(__EMSCRIPTEN__)
+        defined(__EMSCRIPTEN__) ||                                                                                     \
+        defined(__serenity__)
 // clang-format on
 #      define _LIBCPP_HAS_THREAD_API_PTHREAD
 #    elif defined(__Fuchsia__)
 // TODO(44575): Switch to C11 thread API when possible.
 #      define _LIBCPP_HAS_THREAD_API_PTHREAD
 #    elif defined(_LIBCPP_WIN32API)
 #      define _LIBCPP_HAS_THREAD_API_WIN32
 #    else

 #  endif
 
 // Some systems do not provide gets() in their C library, for security reasons.
 #  if defined(_LIBCPP_MSVCRT) || (defined(__FreeBSD_version) && __FreeBSD_version >= 1300043) || defined(__OpenBSD__)
 #    define _LIBCPP_C_HAS_NO_GETS
 #  endif
 
 #  if defined(__BIONIC__) || defined(__NuttX__) || defined(__Fuchsia__) || defined(__wasi__) ||                        \
-      defined(_LIBCPP_HAS_MUSL_LIBC) || defined(__OpenBSD__)
+      defined(_LIBCPP_HAS_MUSL_LIBC) || defined(__OpenBSD__) || defined(__serenity__)
 #    define _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE
 #  endif
 
 #  if __has_feature(cxx_atomic) || __has_extension(c_atomic) || __has_keyword(_Atomic)
 #    define _LIBCPP_HAS_C_ATOMIC_IMP
 #  elif defined(_LIBCPP_COMPILER_GCC)
 #    define _LIBCPP_HAS_GCC_ATOMIC_IMP
 #  endif

libcxx/include/__locale

 # include <xlocale.h>
 #elif defined(__Fuchsia__)
 # include <__support/fuchsia/xlocale.h>
 #elif defined(__wasi__)
 // WASI libc uses musl's locales support.
 # include <__support/musl/xlocale.h>
 #elif defined(_LIBCPP_HAS_MUSL_LIBC)
 # include <__support/musl/xlocale.h>
+#elif defined(__serenity__)
+# include <__support/serenity/xlocale.h>
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 

libcxx/include/__support/serenity/xlocale.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_SERENITY_XLOCALE_H
+#define _LIBCPP_SUPPORT_SERENITY_XLOCALE_H
+
+#if defined(__serenity__)
+
+#  include <__support/xlocale/__nop_locale_mgmt.h>
+#  include <__support/xlocale/__posix_l_fallback.h>
+#  include <__support/xlocale/__strtonum_fallback.h>
+#  include <clocale>
+#  include <cstdlib>
+#  include <ctype.h>
+#  include <cwctype>
+
+#endif // __serenity__
+
+#endif

libcxx/include/locale

 #include <streambuf>
 #include <version>
 
 // TODO: Fix __bsd_locale_defaults.h
 // NOLINTBEGIN(libcpp-robust-against-adl)
 
 #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
 // Most unix variants have catopen.  These are the specific ones that don't.
-#  if !defined(__BIONIC__) && !defined(_NEWLIB_VERSION) && !defined(__EMSCRIPTEN__)
+#  if !defined(__BIONIC__) && !defined(_NEWLIB_VERSION) && !defined(__EMSCRIPTEN__) && !defined(__serenity__)
 #    define _LIBCPP_HAS_CATOPEN 1
 #    include <nl_types.h>
 #  endif
 #endif
 
 #ifdef _LIBCPP_LOCALE__L_EXTENSIONS
 #  include <__locale_dir/locale_base_api/bsd_locale_defaults.h>
 #else

libcxx/src/include/config_elast.h

 #elif defined(__wasi__)
 // No _LIBCPP_ELAST needed on WASI
 #elif defined(__EMSCRIPTEN__)
 // No _LIBCPP_ELAST needed on Emscripten
 #elif defined(__linux__) || defined(_LIBCPP_HAS_MUSL_LIBC)
 #define _LIBCPP_ELAST 4095
 #elif defined(__APPLE__)
 // No _LIBCPP_ELAST needed on Apple
+#elif defined(__serenity__)
+// No _LIBCPP_ELAST needed on SerenityOS
 #elif defined(__MVS__)
 #define _LIBCPP_ELAST 1160
 #elif defined(_LIBCPP_MSVCRT_LIKE)
 #define _LIBCPP_ELAST (_sys_nerr - 1)
 #elif defined(_AIX)
 #define _LIBCPP_ELAST 127
 #else
 // Warn here so that the person doing the libcxx port has an easier time:
 #warning ELAST for this platform not yet implemented
 #endif
 
 #endif // _LIBCPP_CONFIG_ELAST