Add an Extension warning for applying unary * to an operand of type 'void*' in

C++. This seems like a pointless (and indeed harmful) restriction to me, so
I've suggested removing it to -core and disabled this diagnostic by default.

llvm-svn: 208254

1 files changed, 13 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index e4b42402dc5..979c28cbd87 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -9026,10 +9026,6 @@ static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK,
                                      Op->getSourceRange());
   }
 
-  // Note that per both C89 and C99, indirection is always legal, even if OpTy
-  // is an incomplete type or void.  It would be possible to warn about
-  // dereferencing a void pointer, but it's completely well-defined, and such a
-  // warning is unlikely to catch any mistakes.
   if (const PointerType *PT = OpTy->getAs<PointerType>())
     Result = PT->getPointeeType();
   else if (const ObjCObjectPointerType *OPT =
@@ -9048,6 +9044,19 @@ static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK,
     return QualType();
   }
 
+  // Note that per both C89 and C99, indirection is always legal, even if Result
+  // is an incomplete type or void.  It would be possible to warn about
+  // dereferencing a void pointer, but it's completely well-defined, and such a
+  // warning is unlikely to catch any mistakes. In C++, indirection is not valid
+  // for pointers to 'void' but is fine for any other pointer type:
+  //
+  // C++ [expr.unary.op]p1:
+  //   [...] the expression to which [the unary * operator] is applied shall
+  //   be a pointer to an object type, or a pointer to a function type
+  if (S.getLangOpts().CPlusPlus && Result->isVoidType())
+    S.Diag(OpLoc, diag::ext_typecheck_indirection_through_void_pointer)
+      << OpTy << Op->getSourceRange();
+
   // Dereferences are usually l-values...
   VK = VK_LValue;