From e98194d9e8d2ede5eeaa4de411ffe1697ed6a40e Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Sat, 17 Jul 2010 20:43:49 +0000
Subject: [PATCH] Check for casts to an incomplete type in C.  Improves
 diagnostics for cast to incomplete union (PR5692) and incomplete enum, and
 fixes obscure accepts-invalid on cast to incomplete struct.

llvm-svn: 108630
---
 clang/include/clang/Basic/DiagnosticSemaKinds.td |  2 ++
 clang/lib/Sema/SemaExpr.cpp                      |  4 ++++
 clang/test/Sema/cast-incomplete.c                | 14 ++++++++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 clang/test/Sema/cast-incomplete.c

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index ef34fb8ef5a2..9f83406c7213 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2650,6 +2650,8 @@ def err_typecheck_cond_expect_scalar : Error<
   "used type %0 where arithmetic or pointer type is required">;
 def ext_typecheck_cond_one_void : Extension<
   "C99 forbids conditional expressions with only one void side">;
+def err_typecheck_cast_to_incomplete : Error<
+  "cast to incomplete type %0">;
 def ext_typecheck_cast_nonscalar : Extension<
   "C99 forbids casting nonscalar type %0 to the same type">;
 def ext_typecheck_cast_to_union : Extension<"C99 forbids casts to union type">;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index d798d9d0e5c3..2d3aaf6edc05 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3891,6 +3891,10 @@ bool Sema::CheckCastTypes(SourceRange TyR, QualType castType, Expr *&castExpr,
     return false;
   }
 
+  if (RequireCompleteType(TyR.getBegin(), castType,
+                          diag::err_typecheck_cast_to_incomplete))
+    return true;
+
   if (!castType->isScalarType() && !castType->isVectorType()) {
     if (Context.hasSameUnqualifiedType(castType, castExpr->getType()) &&
         (castType->isStructureType() || castType->isUnionType())) {
diff --git a/clang/test/Sema/cast-incomplete.c b/clang/test/Sema/cast-incomplete.c
new file mode 100644
index 000000000000..dd10e00d444a
--- /dev/null
+++ b/clang/test/Sema/cast-incomplete.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -fsyntax-only %s -verify
+// PR5692
+
+enum x;            // expected-note   {{forward declaration}}
+extern struct y a; // expected-note   {{forward declaration}}
+extern union z b;  // expected-note 2 {{forward declaration}}
+
+void foo() {
+  (enum x)1;   // expected-error {{cast to incomplete type}}
+  (struct y)a; // expected-error {{cast to incomplete type}}
+  (union z)b;  // expected-error {{cast to incomplete type}}
+  (union z)1;  // expected-error {{cast to incomplete type}}
+}
+