Re: [PATCH] Make breakpoint subclasses inherit from breakpoint, add virtual destructor

[Pedro Alves <palves@redhat.com>]

On 05/03/2017 03:36 PM, Simon Marchi wrote:
>>> I want to replace the vectors in the various breakpoint subclasses by
>>> std::vector.  The problem right now is that while breakpoint
>>> subclasses are constructed using new, they are not properly deleted.
>>

>> I think "properly deleted" might not be 100% accurate.
> 
> Hmm what do you suggest?  I could say:
> 
>   ... their C++ destructor is not being called.

Yeah.  It's not very important.  I was more referring to the fact that
there's actual destruction of the "subclasses" than talking about
properly-deleted-as-in-the-corresponding-dtor-is-called.

To be crystal clear, I'd put "subclasses" in quotes, and add an example:

~~~
 I want to replace the vectors in the various breakpoint subclasses by
 std::vector.  The problem right now is that while breakpoint
 "subclasses" are constructed using new, they are not properly deleted:

  struct syscall_catchpoint
  {
    /* The base class, old C style.  */
    struct breakpoint base;

    // trivial fields here
  };

  // first member is pointer-interconvertible.
  breakpoint *bp = (breakpoint *) new syscall_catchpoint ();

  // this calls ~breakpoint(), not ~syscall_catchpoint()...
  delete bp;  // in delete_breakpoint

 So if we add any non-trivially destructible field to
 syscall_catchpoint, it won't be properly destructed...
~~~

> You're right, it would be confusing and ugly to leave it with a
> half-baked-dual-hybrid system with C++ destructors and dtor ops.  I'll
> remove the dtor op, it shouldn't be much work, as you said.

Thanks much!

-- 
Pedro Alves