Declaring and initializing a variable in a Conditional or Control statement in C++

Question

In Stroustrup\'s The C++ Programming Language: Special Edition (3rd Ed), Stroustrup writes that the declaration and initialization of variables in the conditionals

Answer 1

I consider it a good style when used with possibly NULL pointer:

if(CObj* p = GetOptionalValue()) {
   //Do something with p
}

This way whether p is declared, it is a valid pointer. No dangling pointer access danger.

On the other hand at least in VC++ it is the only use supported (i.e. checking whether assignment is true)