| // RUN: %clang_cc1 -triple x86_64-windows-msvc %s -emit-llvm -fexceptions -o - | FileCheck %s |
| |
| // PR41065: As background, when constructing a complete object, virtual bases |
| // are constructed first. If an exception is thrown while constructing a |
| // subobject later, those virtual bases are destroyed, so sema references the |
| // relevant constructors and destructors of every base class in case they are |
| // needed. |
| // |
| // However, an abstract class can never be used to construct a complete object. |
| // In the Itanium C++ ABI, this works out nicely, because we never end up |
| // emitting the "complete" constructor variant, only the "base" constructor |
| // variant, which can be called by constructors of derived classes. For various |
| // reasons, Sema does not mark ctors and dtors of virtual bases referenced when |
| // the constructor of an abstract class is emitted. |
| // |
| // In the Microsoft ABI, there are no complete/base variants, so before PR41065 |
| // was fixed, the constructor of an abstract class could reference special |
| // members of a virtual base without marking them referenced. This could lead to |
| // unresolved symbol errors at link time. |
| // |
| // The fix is to implement the same optimization as Sema: If the class is |
| // abstract, don't bother initializing its virtual bases. The "is this class the |
| // most derived class" check in the constructor will never pass, and the virtual |
| // base constructor calls are always dead. Skip them. |
| |
| struct A { |
| A(); |
| virtual void f() = 0; |
| virtual ~A(); |
| }; |
| |
| // B has an implicit inline dtor, but is still abstract. |
| struct B : A { |
| B(int n); |
| int n; |
| }; |
| |
| // Still abstract |
| struct C : virtual B { |
| C(int n); |
| //void f() override; |
| }; |
| |
| // Not abstract, D::D calls C::C and B::B. |
| struct D : C { |
| D(int n); |
| void f() override; |
| }; |
| |
| void may_throw(); |
| C::C(int n) : B(n) { may_throw(); } |
| |
| // No branches, no constructor calls before may_throw(); |
| // |
| // CHECK-LABEL: define dso_local %struct.C* @"??0C@@QEAA@H@Z"(%struct.C* returned %this, i32 %n, i32 %is_most_derived) |
| // CHECK-NOT: br i1 |
| // CHECK-NOT: {{call.*@"\?0}} |
| // CHECK: call void @"?may_throw@@YAXXZ"() |
| // no cleanups |
| |
| |
| D::D(int n) : C(n), B(n) { may_throw(); } |
| |
| // Conditionally construct (and destroy) vbase B, unconditionally C. |
| // |
| // CHECK-LABEL: define dso_local %struct.D* @"??0D@@QEAA@H@Z"(%struct.D* returned %this, i32 %n, i32 %is_most_derived) |
| // CHECK: icmp ne i32 {{.*}}, 0 |
| // CHECK: br i1 |
| // CHECK: call %struct.B* @"??0B@@QEAA@H@Z" |
| // CHECK: br label |
| // CHECK: invoke %struct.C* @"??0C@@QEAA@H@Z" |
| // CHECK: invoke void @"?may_throw@@YAXXZ"() |
| // CHECK: cleanuppad |
| // CHECK: call void @"??1C@@UEAA@XZ" |
| // CHECK: cleanupret |
| // |
| // CHECK: cleanuppad |
| // CHECK: icmp ne i32 {{.*}}, 0 |
| // CHECK: br i1 |
| // CHECK: call void @"??1B@@UEAA@XZ" |
| // CHECK: br label |
| // CHECK: cleanupret |
