[cfe-commits] r131368 - in /cfe/trunk: include/clang/AST/Decl.h lib/AST/Decl.cpp lib/CodeGen/CGCXX.cpp lib/CodeGen/CGClass.cpp test/CodeGenCXX/mangle-subst-std.cpp test/CodeGenCXX/skip-vtable-pointer-initialization.cpp

[Sean Hunt]

On 11-05-14 04:26 PM, Anders Carlsson wrote:
> Author: andersca
> Date: Sat May 14 18:26:09 2011
> New Revision: 131368
>
> URL: http://llvm.org/viewvc/llvm-project?rev=131368&view=rev
> Log:
> When emitting the destructor for a class with a vtable, if we can determine
> that the destructor body is trivial and that all member variables also have either
> trivial destructors or trivial destructor bodies, we don't need to initialize the
> vtable pointers since no virtual member functions will be called on the destructor.
>
> Fixes PR9181.

This breaks the following code:

#include <cstdio>

struct DestroyedBase;
struct Base {
   DestroyedBase *D;
   Base(DestroyedBase *D) : D(D)  { }
   ~Base();
};

struct Derived : Base{
   Derived(DestroyedBase *D) : Base(D) { }
   ~Derived() { }
};

struct DestroyedBase {
   Derived D;
   virtual void Virtual() {
     printf("DestroyedBase::Virtual\n");
   }
   ~DestroyedBase() { }
   DestroyedBase() : D(this) { }
};

struct DestroyedDerived : DestroyedBase {
   virtual void Virtual() {
     printf("DestroyedDerived::Virtual\n");
   }
   ~DestroyedDerived() { }
};

Base::~Base() {
   D->Virtual();
}

int main() { DestroyedDerived D; }

You would need to recursively check all members' bases and members for 
empty destructor bodies too in order to apply this optimization.

Sean