Implement computation of the final overriders for each virtual

function within a class hierarchy (C++ [class.virtual]p2).

We use the final-overrider computation to determine when a particular
class is ill-formed because it has multiple final overriders for a
given virtual function (e.g., because two virtual functions override
the same virtual function in the same virtual base class). Fixes
PR5973.

We also use the final-overrider computation to determine which virtual
member functions are pure when determining whether a class is
abstract or diagnosing the improper use of an abstract class. The
prior approach to determining whether there were any pure virtual
functions in a class didn't cope with virtual base class subobjects
properly, and could not easily be fixed to deal with the oddities of
subobject hiding. Fixes PR6631.

llvm-svn: 99351

1 files changed, 37 insertions, 0 deletions

diff --git a/clang/test/CXX/class.derived/class.virtual/p2.cpp b/clang/test/CXX/class.derived/class.virtual/p2.cpp
new file mode 100644
index 00000000000..64d93c88365
--- /dev/null
+++ b/clang/test/CXX/class.derived/class.virtual/p2.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+struct A {
+  virtual void f() = 0; // expected-note 2{{overridden virtual function}}
+};
+
+struct Aprime : virtual A {
+  virtual void f();
+};
+
+struct B : Aprime {
+  virtual void f(); // expected-note 3{{final overrider of 'A::f'}}
+};
+
+struct C : virtual A {
+  virtual void f(); // expected-note{{final overrider of 'A::f'}}
+};
+
+struct D : B, C { }; // expected-error{{virtual function 'A::f' has more than one final overrider in 'D'}}
+
+struct B2 : B { };
+
+struct E : B, B2 { }; //expected-error{{virtual function 'A::f' has more than one final overrider in 'E'}}
+
+struct F : B, B2 {
+  virtual void f(); // okay
+};
+
+struct G : F { }; // okay
+
+struct H : G, A { }; // okay
+
+namespace MultipleSubobjects {
+  struct A { virtual void f(); };
+  struct B : A { virtual void f(); };
+  struct C : A { virtual void f(); };
+  struct D : B, C { }; // okay
+}