Sema: do not attempt to sizeof a dependent type

We would attempt to evaluate the sizeof a dependent type to check for an
integral overflow.  However, because the dependent type is not yet resolved, we
cannot determine if the expression would overflow.  Report a failure to perform
a symbolic evaluation of a constant involving the dependent type.

llvm-svn: 271762

Author: compnerd

clang/lib/AST/ExprConstant.cpp

@@ -2024,6 +2024,11 @@ static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
     return true;
   }
 
+  if (Type->isDependentType()) {
+    Info.Diag(Loc);
+    return false;
+  }
+
   if (!Type->isConstantSizeType()) {
     // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
     // FIXME: Better diagnostic.

clang/test/SemaCXX/eval-sizeof-dependent-type.cpp

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -std=c++11 -x c++ %s
+
+typedef __SIZE_TYPE__ size_t;
+template <typename _Tp, size_t _Nm> struct array { _Tp _M_elems[_Nm]; };
+template <typename T> struct s {
+  array<int, 1> v{static_cast<int>(sizeof (T) / sizeof(T))};
+};
+