[www] Update attribute reference for 'constinit'.

llvm-svn: 370986

2 files changed, 11 insertions, 3 deletions

diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index fbf26ec9b95..e31f3cd9b26 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -918,7 +918,7 @@ def ConstInit : InheritableAttr {
                    Clang<"require_constant_initialization", 0>];
   let Subjects = SubjectList<[GlobalVar], ErrorDiag>;
   let Accessors = [Accessor<"isConstinit", [Keyword<"constinit">]>];
-  let Documentation = [RequireConstantInitDocs];
+  let Documentation = [ConstInitDocs];
   let LangOpts = [CPlusPlus];
 }
 
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 6732e3db8f7..103bc8b9d3b 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -1408,15 +1408,17 @@ all optional, but the attribute has to have at least one clause.
   }];
 }
 
-def RequireConstantInitDocs : Documentation {
+def ConstInitDocs : Documentation {
   let Category = DocCatVariable;
+  let Heading = "require_constant_initialization, constinit (C++20)";
   let Content = [{
 This attribute specifies that the variable to which it is attached is intended
 to have a `constant initializer <http://en.cppreference.com/w/cpp/language/constant_initialization>`_
 according to the rules of [basic.start.static]. The variable is required to
 have static or thread storage duration. If the initialization of the variable
 is not a constant initializer an error will be produced. This attribute may
-only be used in C++.
+only be used in C++; the ``constinit`` spelling is only accepted in C++20
+onwards.
 
 Note that in C++03 strict constant expression checking is not done. Instead
 the attribute reports if Clang can emit the variable as a constant, even if it's
@@ -1431,6 +1433,12 @@ for constant initialization have been met. Since these requirements change
 between dialects and have subtle pitfalls it's important to fail fast instead
 of silently falling back on dynamic initialization.
 
+The first use of the attribute on a variable must be part of, or precede, the
+initializing declaration of the variable. C++20 requires the ``constinit``
+spelling of the attribute to be present on the initializing declaration if it
+is used anywhere. The other spellings can be specified on a forward declaration
+and omitted on a later initializing declaration.
+
 .. code-block:: c++
 
   // -std=c++14