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

llvm-svn: 314456

3 files changed, 15 insertions, 1 deletions

diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index c3567709ee0..17d2be28611 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/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/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 0500c283861..e51c65073fe 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/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 = [{
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index 7529a2425d3..da024a43947 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -40,6 +40,7 @@
 // CHECK-NEXT: NoSanitize (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_variable_is_global)
 // CHECK-NEXT: NoSanitizeSpecific (SubjectMatchRule_function, SubjectMatchRule_variable_is_global)
 // CHECK-NEXT: NoSplitStack (SubjectMatchRule_function)
+// CHECK-NEXT: NoThrow (SubjectMatchRule_function)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: ObjCBoxable (SubjectMatchRule_record)
 // CHECK-NEXT: ObjCMethodFamily (SubjectMatchRule_objc_method)