[webkit-dev] Ptr<T>

Darin Adler darin at apple.com
Wed Aug 11 09:12:29 PDT 2010

On Aug 7, 2010, at 8:59 PM, Eric Seidel wrote:

> How about we add a Ptr<T> (or WeakPtr<T> or AutoNull<T> or whatever)

I worked on another project years ago where they had a template like this. The issue is with a variety of built-in data types, not specific to pointers. Any built-in data type such as a pointer, integer, or floating point number where it's not initialized by default can instead be initialized like this:

    , m_member()

That syntax will zero-initialize it. So if you have a template like this you can use it to take care of zero-initialization for any of these types. (For integers you can even go further and have the template specify the initial value which means you won’t have to repeat that value in multiple constructors.)

So much for the up-side of a template like this.

The downside is that the object does not have the type we might think it does. Even if we add assignment operators, conversion constructors and operators in both directions, it can still give us an unpleasant result in any context where overloading is involved, such as calling an overloaded function, and we might need an explicit function to get the actual scalar value, analogous to the get function we use on smart pointer.

I’m not sure if in practice this “initialize me” template will improve things much; remembering to use it is not all that much easier than remembering to initialize in constructors, but I don’t object strongly to the notion.

    -- Darin

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