Currently we're initializing the vtable pointers of a class only after
the bases are completely initialized. This won't work --- base
initializer expressions can rely on the vtables having been set up.
Check for uses of 'this' in the initializers and force a vtable
initialization if found.
This might not be good enough; we might need to extend this to handle
the possibility of arbitrary code finding an external reference to this
(not yet completely-constructed!) object and accessing through it,
in which case we'll probably find ourselves doing a lot more unnecessary
stores.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@114153 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index a6ac0ac..c8f23f3 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -14,6 +14,7 @@
#include "CGDebugInfo.h"
#include "CodeGenFunction.h"
#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtCXX.h"
@@ -334,6 +335,29 @@
CGF.EmitCXXDestructorCall(D, Dtor_Base, BaseIsVirtual, Addr);
}
};
+
+ /// A visitor which checks whether an initializer uses 'this' in a
+ /// way which requires the vtable to be properly set.
+ struct DynamicThisUseChecker : EvaluatedExprVisitor<DynamicThisUseChecker> {
+ typedef EvaluatedExprVisitor<DynamicThisUseChecker> super;
+
+ bool UsesThis;
+
+ DynamicThisUseChecker(ASTContext &C) : super(C), UsesThis(false) {}
+
+ // Black-list all explicit and implicit references to 'this'.
+ //
+ // Do we need to worry about external references to 'this' derived
+ // from arbitrary code? If so, then anything which runs arbitrary
+ // external code might potentially access the vtable.
+ void VisitCXXThisExpr(CXXThisExpr *E) { UsesThis = true; }
+ };
+}
+
+static bool BaseInitializerUsesThis(ASTContext &C, const Expr *Init) {
+ DynamicThisUseChecker Checker(C);
+ Checker.Visit(const_cast<Expr*>(Init));
+ return Checker.UsesThis;
}
static void EmitBaseInitializer(CodeGenFunction &CGF,
@@ -355,6 +379,12 @@
if (CtorType == Ctor_Base && isBaseVirtual)
return;
+ // If the initializer for the base (other than the constructor
+ // itself) accesses 'this' in any way, we need to initialize the
+ // vtables.
+ if (BaseInitializerUsesThis(CGF.getContext(), BaseInit->getInit()))
+ CGF.InitializeVTablePointers(ClassDecl);
+
// We can pretend to be a complete class because it only matters for
// virtual bases, and we only do virtual bases for complete ctors.
llvm::Value *V =