Variable Sized Struct C++

Question

Is this the best way to make a variable sized struct in C++? I don\'t want to use vector because the length doesn\'t change after initialization.

struct Pack         


        

Answer 1

This is OK (and was standard practice for C).

But this is not a good idea for C++.
This is because the compiler generates a whole set of other methods automatically for you around the class. These methods do not understand that you have cheated.

For Example:

void copyRHSToLeft(Packet& lhs,Packet& rhs)
{
    lhs = rhs;  // The compiler generated code for assignement kicks in here.
                // Are your objects going to cope correctly??
}


Packet*   a = CreatePacket(3);
Packet*   b = CreatePacket(5);
copyRHSToLeft(*a,*b);

Use the std::vector<> it is much safer and works correctly.
I would also bet it is just as efficient as your implementation after the optimizer kicks in.

Alternatively boost contains a fixed size array:
http://www.boost.org/doc/libs/1_38_0/doc/html/array.html