Add Documentation to attribute-nothrow. Additionally, limit to functions.

Attribute nothrow is only allowed on functions, so I added that. Additionally,
it lacks any documentation, so I added some.

Differential Revision: https://reviews.llvm.org/D38202


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314456 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 14 insertions, 1 deletions

diff --git a/include/clang/Basic/Attr.td b/include/clang/Basic/Attr.td
index c3567709ee..17d2be2861 100644
--- a/include/clang/Basic/Attr.td
+++ b/include/clang/Basic/Attr.td
@@ -1437,7 +1437,8 @@ def NotTailCalled : InheritableAttr {
 
 def NoThrow : InheritableAttr {
   let Spellings = [GCC<"nothrow">, Declspec<"nothrow">];
-  let Documentation = [Undocumented];
+  let Subjects = SubjectList<[Function]>;
+  let Documentation = [NoThrowDocs];
 }
 
 def NvWeak : IgnoredAttr {
diff --git a/include/clang/Basic/AttrDocs.td b/include/clang/Basic/AttrDocs.td
index 0500c28386..e51c65073f 100644
--- a/include/clang/Basic/AttrDocs.td
+++ b/include/clang/Basic/AttrDocs.td
@@ -2727,6 +2727,18 @@ Marking virtual functions as ``not_tail_called`` is an error:
   }];
 }
 
+def NoThrowDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the GNU style ``__attribute__((nothrow))`` and Microsoft style
+``__declspec(nothrow)`` attribute as an equivilent of `noexcept` on function
+declarations. This attribute informs the compiler that the annotated function
+does not throw an exception. This prevents exception-unwinding. This attribute
+is particularly useful on functions in the C Standard Library that are
+guaranteed to not throw an exception.
+    }];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{