[clang][Interp] Diagnose uninitialized bases (#67131)

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -561,7 +561,7 @@ bool ByteCodeExprGen<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
         if (!this->visitInitializer(Init))
           return false;
 
-        if (!this->emitPopPtr(E))
+        if (!this->emitInitPtrPop(E))
           return false;
         // Base initializers don't increase InitIndex, since they don't count
         // into the Record's fields.
@@ -1718,7 +1718,7 @@ bool ByteCodeExprGen<Emitter>::visitZeroRecordInitializer(const Record *R,
       return false;
     if (!this->visitZeroRecordInitializer(B.R, E))
       return false;
-    if (!this->emitPopPtr(E))
+    if (!this->emitInitPtrPop(E))
       return false;
   }
 

clang/lib/AST/Interp/ByteCodeStmtGen.cpp

@@ -191,7 +191,7 @@ bool ByteCodeStmtGen<Emitter>::visitFunc(const FunctionDecl *F) {
           return false;
         if (!this->visitInitializer(InitExpr))
           return false;
-        if (!this->emitPopPtr(InitExpr))
+        if (!this->emitInitPtrPop(InitExpr))
           return false;
       }
     }

clang/lib/AST/Interp/Interp.cpp

@@ -467,6 +467,12 @@ static bool CheckFieldsInitialized(InterpState &S, CodePtr OpPC,
   // Check Fields in all bases
   for (const Record::Base &B : R->bases()) {
     Pointer P = BasePtr.atField(B.Offset);
+    if (!P.isInitialized()) {
+      S.FFDiag(BasePtr.getDeclDesc()->asDecl()->getLocation(),
+               diag::note_constexpr_uninitialized_base)
+          << B.Desc->getType();
+      return false;
+    }
     Result &= CheckFieldsInitialized(S, OpPC, P, B.R);
   }
 

clang/lib/AST/Interp/Interp.h

@@ -1245,6 +1245,12 @@ inline bool GetPtrThisBase(InterpState &S, CodePtr OpPC, uint32_t Off) {
   return true;
 }
 
+inline bool InitPtrPop(InterpState &S, CodePtr OpPC) {
+  const Pointer &Ptr = S.Stk.pop<Pointer>();
+  Ptr.initialize();
+  return true;
+}
+
 inline bool VirtBaseHelper(InterpState &S, CodePtr OpPC, const RecordDecl *Decl,
                            const Pointer &Ptr) {
   Pointer Base = Ptr;

clang/lib/AST/Interp/Opcodes.td

@@ -304,6 +304,10 @@ def GetPtrBasePop : Opcode {
   let Args = [ArgUint32];
 }
 
+def InitPtrPop : Opcode {
+  let Args = [];
+}
+
 def GetPtrDerivedPop : Opcode {
   let Args = [ArgUint32];
 }

clang/test/AST/Interp/constexpr-subobj-initialization.cpp

@@ -0,0 +1,73 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -fexperimental-new-constant-interpreter
+
+/// This is like the version in test/SemaCXX/, but some of the
+/// output types and their location has been adapted.
+/// Differences:
+///   1) The type of the uninitialized base class is printed WITH the namespace,
+///      i.e. 'baseclass_uninit::DelBase' instead of just 'DelBase'.
+///   2) The location is not the base specifier declaration, but the call site
+///      of the constructor.
+
+
+namespace baseclass_uninit {
+struct DelBase {
+  constexpr DelBase() = delete; // expected-note {{'DelBase' has been explicitly marked deleted here}}
+};
+
+struct Foo : DelBase {
+  constexpr Foo() {}; // expected-error {{call to deleted constructor of 'DelBase'}}
+};
+constexpr Foo f; // expected-error {{must be initialized by a constant expression}} \
+                 // expected-note {{constructor of base class 'baseclass_uninit::DelBase' is not called}}
+
+struct Bar : Foo {
+  constexpr Bar() {};
+};
+constexpr Bar bar; // expected-error {{must be initialized by a constant expression}} \
+                   // expected-note {{constructor of base class 'baseclass_uninit::DelBase' is not called}}
+
+struct Base {};
+struct A : Base {
+  constexpr A() : value() {} // expected-error {{member initializer 'value' does not name a non-static data member or base class}}
+};
+
+constexpr A a; // expected-error {{must be initialized by a constant expression}} \
+               // expected-note {{constructor of base class 'baseclass_uninit::Base' is not called}}
+
+
+struct B : Base {
+  constexpr B() : {} // expected-error {{expected class member or base class name}}
+};
+
+constexpr B b; // expected-error {{must be initialized by a constant expression}} \
+               // expected-note {{constructor of base class 'baseclass_uninit::Base' is not called}}
+} // namespace baseclass_uninit
+
+
+struct Foo {
+  constexpr Foo(); // expected-note 2{{declared here}}
+};
+
+constexpr Foo ff; // expected-error {{must be initialized by a constant expression}} \
+                  // expected-note {{undefined constructor 'Foo' cannot be used in a constant expression}}
+
+struct Bar : protected Foo {
+  int i;
+  constexpr Bar() : i(12) {} // expected-note {{undefined constructor 'Foo' cannot be used in a constant expression}}
+};
+
+constexpr Bar bb; // expected-error {{must be initialized by a constant expression}} \
+                  // expected-note {{in call to 'Bar()'}}
+
+template <typename Ty>
+struct Baz {
+  constexpr Baz(); // expected-note {{declared here}}
+};
+
+struct Quux : Baz<Foo>, private Bar {
+  int i;
+  constexpr Quux() : i(12) {} // expected-note {{undefined constructor 'Baz' cannot be used in a constant expression}}
+};
+
+constexpr Quux qx; // expected-error {{must be initialized by a constant expression}} \
+                   // expected-note {{in call to 'Quux()'}}