Should Local Variable Initialisation Be Mandatory?

Question

The maintenance problems that uninitialised locals cause (particularly pointers) will be obvious to anyone who has done a bit of c/c++ maintenance or enhancement, but I still se

Answer 1

This pertains to C++ only, but there is a definite distinction between the two methods. Let's assume you have a class MyStuff, and you want to initialize it by another class. You could do something like:

// Initialize MyStuff instance y
// ...
MyStuff x = y;
// ...

What this actually does is call the copy constructor of x. It's the same as:

MyStuff x(y);

This is different than this code:

MyStuff x; // This calls the MyStuff default constructor.
x = y; // This calls the MyStuff assignment operator.

Of course, completely different code is called when copy constructing vs. default constructing + assigning. Also, a single call to the copy constructor is likely to be more efficient than construction followed by assignment.