try {.... } catch(..) only if a certain compile time expression is true

Question

Here is what we are trying to do

try {
    std::uninitialized_copy(...);
} catch(...) {
    if(!boost::has_trivial_destructor<T>::value) {
       // some cleanup to do here...
    }
    throw;
}

We wonder whether the try/catch has a cost if the compile time constant in the if is false.

Can the compiler within its "as-if" rights remove the try catch and behave as-if the std::uninitialized_copy call appeared without try around it?

Or is there something hidden in the C++ specs that requires the compiler to leave it here? As an example, imagine a hypothetical surrounding_try_blocks() function that returns the dynamic surrounding try blocks count currently around a frame.

Answer 1

I have no idea what the compiler will do but I know that you can enforce the optimization by yourself:

template <class T>
typename boost::enable_if_t<boost::has_trivial_destructor<T>::value, void>
wrap_uninitialized_copy (...) {
    std::uninitialized_copy(...);
}

template <class T>
typename boost::enable_if_t<!boost::has_trivial_destructor<T>::value, void>
wrap_uninitialized_copy (...) {
    try {
        std::uninitialized_copy(...);
    } catch(...) {
        // some cleanup to do here...
        throw;
    }
}