Sema: Disallow inheriting from classes with flexible array members
Flexible array members inherently index off of the end of their parent
type.
We shouldn't allow this type to be used as a base, virtual or otherwise,
because indexing off the end may find us inside of another base or the
derived types members.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193923 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index ef78cc9..092d584 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5885,6 +5885,8 @@
def err_union_as_base_class : Error<"unions cannot be base classes">;
def err_circular_inheritance : Error<
"circular inheritance between %0 and %1">;
+def err_base_class_has_flexible_array_member : Error<
+ "base class %0 has a flexible array member">;
def err_incomplete_base_class : Error<"base class has incomplete type">;
def err_duplicate_base_class : Error<
"base class %0 specified more than once as a direct base class">;
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index dce0592..c833835 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -1370,6 +1370,18 @@
CXXRecordDecl *CXXBaseDecl = cast<CXXRecordDecl>(BaseDecl);
assert(CXXBaseDecl && "Base type is not a C++ type");
+ // A class which contains a flexible array member is not suitable for use as a
+ // base class:
+ // - If the layout determines that a base comes before another base,
+ // the flexible array member would index into the subsequent base.
+ // - If the layout determines that base comes before the derived class,
+ // the flexible array member would index into the derived class.
+ if (CXXBaseDecl->hasFlexibleArrayMember()) {
+ Diag(BaseLoc, diag::err_base_class_has_flexible_array_member)
+ << CXXBaseDecl->getDeclName();
+ return 0;
+ }
+
// C++ [class]p3:
// If a class is marked final and it appears as a base-type-specifier in
// base-clause, the program is ill-formed.