commit 8925814d87af15e819ee9e61920466d087679212
author Louis Dionne <ldionne.2@gmail.com> Mon Aug 23 15:32:36 2021 -0400
committer Copybara-Service <copybara-worker@google.com> Tue Oct 12 03:10:37 2021 -0700
tree be6b6c8326a97e5b82b92d3103baa38723f2e730
parent af0093d83f19c6770b43900cadb2bb74646c2ea3

[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

include/string

diff --git a/include/string b/include/string
index c6a799d..53b4e09 100644
--- a/include/string
+++ b/include/string
@@ -524,7 +524,6 @@
 #include <cstdio>  // EOF
 #include <cstdlib>
 #include <cstring>
-#include <cwchar>
 #include <initializer_list>
 #include <iosfwd>
 #include <iterator>
@@ -535,6 +534,10 @@
 #include <utility>
 #include <version>
 
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#   include <cwchar>
+#endif
+
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 # include <cstdint>
 #endif
@@ -1729,11 +1732,15 @@
 // These declarations must appear before any functions are implicitly used
 // so that they have the correct visibility specifier.
 #ifdef _LIBCPP_ABI_STRING_OPTIMIZED_EXTERNAL_INSTANTIATION
-_LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, char)
-_LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, wchar_t)
+    _LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, char)
+#   ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+        _LIBCPP_STRING_UNSTABLE_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, wchar_t)
+#   endif
 #else
-_LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, char)
-_LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, wchar_t)
+    _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, char)
+#   ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+        _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_EXTERN_TEMPLATE, wchar_t)
+#   endif
 #endif
 
 
@@ -4395,6 +4402,7 @@
 _LIBCPP_FUNC_VIS string to_string(double __val);
 _LIBCPP_FUNC_VIS string to_string(long double __val);
 
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 _LIBCPP_FUNC_VIS int                stoi  (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
 _LIBCPP_FUNC_VIS long               stol  (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
 _LIBCPP_FUNC_VIS unsigned long      stoul (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
@@ -4414,6 +4422,7 @@
 _LIBCPP_FUNC_VIS wstring to_wstring(float __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(double __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(long double __val);
+#endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
 
 template<class _CharT, class _Traits, class _Allocator>
 _LIBCPP_TEMPLATE_DATA_VIS
@@ -4535,11 +4544,13 @@
         return basic_string<char> (__str, __len);
     }
 
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
     inline _LIBCPP_INLINE_VISIBILITY
     basic_string<wchar_t> operator "" s( const wchar_t *__str, size_t __len )
     {
         return basic_string<wchar_t> (__str, __len);
     }
+#endif
 
 #ifndef _LIBCPP_HAS_NO_CHAR8_T
     inline _LIBCPP_INLINE_VISIBILITY