Question

Are there any downsides with using make_shared<T>() instead of using shared_ptr<T>(new T).

Boost documentation states

There have been repeated requests from
users for a factory function that
creates an object of a given type and
returns a shared_ptr to it. Besides
convenience and style, such a function
is also exception safe and
considerably faster because it can use
a single allocation for both the
object and its corresponding control
block, eliminating a significant
portion of shared_ptr’s construction
overhead. This eliminates one of the
major efficiency complaints about
shared_ptr.

Answer 1

I know of at least two.

• You must be in control of the allocation. Not a big one really, but some older api’s like to return pointers that you must delete.
• No custom deleter. I don’t know why this isn’t supported, but it isn’t. That means your shared pointers have to use a vanilla deleter.

Pretty weak points. so try to always use make_shared.