[gpderetta]

It is complicated. In C++ closures can close over local variables either by value or by reference (the choice can be made for each variable closed over).

When closing over a variable by reference, if the lambda need to survive the local scope heap allocating the closure itself won't help. Instead you need to explicitly heap allocate the closed over variable itself (and close over the, usually smart, pointer).

When closing over by vale, there is no such issue, closed over variables are copied over along the lambda and it can be safely, for example, be returned from a function.

Copying might be expensive if the lambda is closing over an expensive to copy object, but move semantics are always an option.

Lambdas are value types, they are usually copied around. so when closing over ither va