P0188R1: add support for standard [[fallthrough]] attribute. This is almost

exactly the same as clang's existing [[clang::fallthrough]] attribute, which
has been updated to have the same semantics. The one significant difference
is that [[fallthrough]] is ill-formed if it's not used immediately before a
switch label (even when -Wimplicit-fallthrough is disabled). To support that,
we now build a CFG of any function that uses a '[[fallthrough]];' statement
to check.

In passing, fix some bugs with our support for statement attributes -- in
particular, diagnose their use on declarations, rather than asserting.

llvm-svn: 262881

1 files changed, 9 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index ce78ab00926..1fca27f8b95 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -2467,7 +2467,7 @@ static void handleWarnUnusedResult(Sema &S, Decl *D, const AttributeList &Attr)
   // about using it as an extension.
   if (!S.getLangOpts().CPlusPlus1z && Attr.isCXX11Attribute() &&
       !Attr.getScopeName())
-    S.Diag(Attr.getLoc(), diag::ext_nodiscard_attr_is_a_cxx1z_extension);
+    S.Diag(Attr.getLoc(), diag::ext_cxx1z_attr) << Attr.getName();
 
   D->addAttr(::new (S.Context) 
              WarnUnusedResultAttr(Attr.getRange(), S.Context,
@@ -5072,7 +5072,7 @@ static void handleDeprecatedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   if (!S.getLangOpts().CPlusPlus14)
     if (Attr.isCXX11Attribute() &&
         !(Attr.hasScope() && Attr.getScopeName()->isStr("gnu")))
-      S.Diag(Attr.getLoc(), diag::ext_deprecated_attr_is_a_cxx14_extension);
+      S.Diag(Attr.getLoc(), diag::ext_cxx14_attr) << Attr.getName();
 
   handleAttrWithMessage<DeprecatedAttr>(S, D, Attr);
 }
@@ -5234,8 +5234,13 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
 
   switch (Attr.getKind()) {
   default:
-    // Type attributes are handled elsewhere; silently move on.
-    assert(Attr.isTypeAttr() && "Non-type attribute not handled");
+    if (!Attr.isStmtAttr()) {
+      // Type attributes are handled elsewhere; silently move on.
+      assert(Attr.isTypeAttr() && "Non-type attribute not handled");
+      break;
+    }
+    S.Diag(Attr.getLoc(), diag::err_stmt_attribute_invalid_on_decl)
+        << Attr.getName() << D->getLocation();
     break;
   case AttributeList::AT_Interrupt:
     handleInterruptAttr(S, D, Attr);