You have to think of shared_ptr as a template class whos job is to handle the lifecycle of a pointer.

NULL is just a typedef which is defined as:

It's not some sort of special type in the language.

So when you say:

it thinks your trying to convert an integer to your type foo.
I think this might actually work if your class foo had overloaded the = operator to handle integers on the right side.


does not work because shared_ptr is trying to find a constructor for foo which takes an integer as a parameter.

so basically if you want to make a NULL shared_ptr

is the correct thing to do.

The first problem you come across is caused because the '=' operator on a shared_ptr is overloaded to accept another shared_ptr, not a raw pointer.

First make sure that NULL is defined, I don't use the Win32 Lib's so I have to define it myself.

Whenever I want to make a blank shared_ptr I just construct it without a parameter like you did and the class is set up to automatically NULL the internal pointer.

I don't see why putting NULL in the parameter list would give you that error, to show you what it is looking for though this is how the template works.

The shared_ptr has alot of overloaded constructors, but in this case it would look something like this



So when you put a class in this happens



So you should have no problem passing in a NULL pointer

error C2440: '<function-style-cast>' : cannot convert from 'int' to 'std::tr1::shared_ptr<_Ty>'

This error may be because there was no appropriate constructor found for an integer value (your NULL integer), so the compiler is interpreting it as a function style cast, do a quick google search on 'function style cast error' , there are some things that aren't safe to do in Visual Studio, and I believe you have to be careful with function style casts

NULL is just a typedef which is defined as:

Source Code

1. typedef NULL 0

I don't think that would work, what you are saying is to make a new type called '0' which is in reference to the NULL constant. You can't start variables or functions with a number in C++ , and the typedef it more for simplifying longer types like



NULL will either be


Correct me if I'm wrong

You're right, it should be the #define

That's what I get for trying to think to hard right after I wake up, hah!

lol