[libc++] Add an option to disable wide character support in libc++
Some embedded platforms do not wish to support the C library functionality
for handling wchar_t because they have no use for it. It makes sense for
libc++ to work properly on those platforms, so this commit adds a carve-out
of functionality for wchar_t.
Unfortunately, unlike some other carve-outs (e.g. random device), this
patch touches several parts of the library. However, despite the wide
impact of this patch, I still think it is important to support this
configuration since it makes it much simpler to port libc++ to some
embedded platforms.
Differential Revision: https://reviews.llvm.org/D111265
NOKEYCHECK=True
GitOrigin-RevId: f4c1258d5633fcf06385ff3fd1f4bf57ab971964
diff --git a/docs/BuildingLibcxx.rst b/docs/BuildingLibcxx.rst
index a29a05b..a0128b8 100644
--- a/docs/BuildingLibcxx.rst
+++ b/docs/BuildingLibcxx.rst
@@ -251,6 +251,15 @@
This option can be used to enable or disable the filesystem components on
platforms that may not support them. For example on Windows when using MSVC.
+.. option:: LIBCXX_ENABLE_WIDE_CHARACTERS:BOOL
+
+ **Default**: ``ON``
+
+ This option can be used to disable support for ``wchar_t`` in the library. It also
+ allows the library to work on top of a C Standard Library that does not provide
+ support for ``wchar_t``. This is especially useful in embedded settings where
+ C Standard Libraries don't always provide all the usual bells and whistles.
+
.. option:: LIBCXX_ENABLE_INCOMPLETE_FEATURES:BOOL
**Default**: ``ON``