[libcxx-commits] [clang] [libcxx] [clang][WIP] std::embed and #depend implementation (PR #190578)

[Hristo Hristov via libcxx-commits]

================
@@ -0,0 +1,113 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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_EMBED
+#define _LIBCPP_EMBED
+
+/*
+    embed synopsis
+
+namespace std {
+
+  template <typename T>
+consteval span<const T> embed(string_view resource_idenfier,
+  size_t offset = 0,
+  optional<size_t> limit = nullopt);
+
+  template <typename T>
+consteval span<const T> embed(wstring_view resource_idenfier,
+  size_t offset = 0,
+  optional<size_t> limit = nullopt);
+
+  template <typename T>
+consteval span<const T> embed(u8string_view resource_idenfier,
+  size_t offset = 0,
+  optional<size_t> limit = nullopt);
+
+} // namespace std
+
+*/
+
+#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
+#  include <__cxx03/__config>
+#else
+#  include <__config>
+#  include <__cstddef/byte.h>
+#  include <__type_traits/is_enum.h>
+#  include <__type_traits/is_integral.h>
+#  include <__type_traits/is_same.h>
+#  include <optional>
+#  include <span>
+#  include <string_view>
+#  include <version>
+
+#  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#    pragma GCC system_header
+#  endif
+
+_LIBCPP_PUSH_MACROS
+#  include <__undef_macros>
+
+#  if !defined(_LIBCPP_HAS_EMBED)
+#    if __has_builtin(__builtin_std_embed)
+#      define _LIBCPP_HAS_EMBED 1
+#    else
+#      define _LIBCPP_HAS_EMBED 0
+#    endif
+#  endif
+
+#  if _LIBCPP_HAS_EMBED != 0
----------------
H-G-Hristov wrote:

Why is this macro needed? I think a guard around the code with this pattern is all that's needed:

```c++
#if _LIBCPP_STD_VER > 26 && __has_builtin(__builtin_std_embed)
...
#endif // _LIBCPP_STD_VER > 26 && __has_builtin(__builtin_std_embed)
```
e.g.
https://github.com/llvm/llvm-project/blob/main/libcxx/include/__type_traits/is_within_lifetime.h#L20

+ tests.

https://github.com/llvm/llvm-project/pull/190578