Why is a vector of pointers not castable to a const vector of const pointers?

Question

The type vector is not convertible to const vector. For example, the following gives a compilation error:

Answer 1

As the FQA suggests, this is a fundamental flaw in C++.

It appears that you can do what you want by some explicit casting:

vector vc = vector(); 
vector* vcc = reinterpret_cast*>(&vc);
fn(*vcc);

This invokes Undefined Behavior and is not guaranteed to work; however, I am almost certain it will work in gcc with strict aliasing turned off (-fno-strict-aliasing). In any case, this can only work as a temporary hack; you should just copy the vector to do what you want in a guaranteed manner.

std::copy(vc.begin(), vc.end(), std::back_inserter(vcc));

This is OK also from the performance perspective, because fn copies its parameter when it's called.