Are temporary objects in C++ const indeed?

Question

I always believed that temporary objects in C++ are automatically considered as const by the compiler. But recently I experienced that the following example of code:

Answer 1

Answering the question first, they are not actually const. You may not bind one to a non-const reference. This was probably done to prevent errors in certain situations where they would be passed as a parameter to a function that modifies them, only for the changes to be made to a temporary object and not the intended target.

Allowing non-const operations on a temporary is especially useful when you wish to call "swap" on it with a local variable.

std::vector local;
method_that_returns_a_vector().swap( local );

Before the days of move semantics, this was considered the most efficient way to return a large data set and acquire it without copying all the data.