invasive vs non-invasive ref-counted pointers in C++
- by anon
For the past few years, I've generally accepted that
if I am going to use ref-counted smart pointers
invasive smart pointers is the way to go
--
However, I'm starting to like non-invasive smart pointers due to the following:
I only use smart pointers (so no Foo* lying around, only Ptr)
I'm starting to build custom allocators for each class. (So Foo would overload operator new).
Now, if Foo has a list of all Ptr (as it easily can with non-invasive smart pointers).
Then, I can avoid memory fragmentation issues since class Foo move the objects around (and just update the corresponding Ptr).
The only reason why this Foo moving objects around in non-invasive smart pointers being easier than invasive smart pointers is:
In non-invasive smart pointers, there is only one pointer that points to each Foo.
In invasive smart pointers, I have no idea how many objects point to each Foo.
Now, the only cost of non-invasive smart pointers ... is the double indirection. [Perhaps this screws up the caches].
Does anyone have a good study of expensive this extra layer of indirection is?
