Sema: Don't permit variably modified types in typeid

GCC and ICC both reject this and the 'Runtime-sized arrays with
automatic storage duration' (N3639) paper forbade this as well.
Previously, we would crash on our way to mangling.

This fixes PR21632.

llvm-svn: 222569

3 files changed, 14 insertions, 0 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 310a9b2a2ff..9639b3ce42c 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5303,6 +5303,7 @@ def err_uuidof_without_guid : Error<
 def err_uuidof_with_multiple_guids : Error<
   "cannot call operator __uuidof on a type with multiple GUIDs">;
 def err_incomplete_typeid : Error<"'typeid' of incomplete type %0">;
+def err_variably_modified_typeid : Error<"'typeid' of variably modified type %0">;
 def err_static_illegal_in_new : Error<
   "the 'static' modifier for the array size is not legal in new expressions">;
 def err_array_new_needs_size : Error<
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 93996685105..c71a4e93bbd 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -384,6 +384,9 @@ ExprResult Sema::BuildCXXTypeId(QualType TypeInfoType,
       RequireCompleteType(TypeidLoc, T, diag::err_incomplete_typeid))
     return ExprError();
 
+  if (T->isVariablyModifiedType())
+    return ExprError(Diag(TypeidLoc, diag::err_variably_modified_typeid) << T);
+
   return new (Context) CXXTypeidExpr(TypeInfoType.withConst(), Operand,
                                      SourceRange(TypeidLoc, RParenLoc));
 }
@@ -438,6 +441,10 @@ ExprResult Sema::BuildCXXTypeId(QualType TypeInfoType,
     }
   }
 
+  if (E->getType()->isVariablyModifiedType())
+    return ExprError(Diag(TypeidLoc, diag::err_variably_modified_typeid)
+                     << E->getType());
+
   return new (Context) CXXTypeidExpr(TypeInfoType.withConst(), E,
                                      SourceRange(TypeidLoc, RParenLoc));
 }
diff --git a/clang/test/SemaCXX/typeid.cpp b/clang/test/SemaCXX/typeid.cpp
index d3a2a28deb8..48fcce0b492 100644
--- a/clang/test/SemaCXX/typeid.cpp
+++ b/clang/test/SemaCXX/typeid.cpp
@@ -21,3 +21,9 @@ void g1(X &x) {
   (void)typeid(X&); // expected-error{{'typeid' of incomplete type 'X'}}
   (void)typeid(x); // expected-error{{'typeid' of incomplete type 'X'}}
 }
+
+void h(int i) {
+  char V[i];
+  typeid(V);        // expected-error{{'typeid' of variably modified type 'char [i]'}}
+  typeid(char [i]); // expected-error{{'typeid' of variably modified type 'char [i]'}}
+}