C++ Create a class instance and pointer to it in one line

Question

There is a one line syntax to create an instance and pointer to it, in the heap allocation. Is there one line syntax for the same purpose but with stack allocation?

#include <iostream>

class Base {};

int main()
{
    //Base* ptr = new Base(); // heap

    Base base;
    Base* ptr = &base; // stack  

    return 0;
}

I have no problem to use 2 lines, just thought maybe there is a special syntax for this case (I'm moving from Python :D)

It is possible to define more than one variable in a single declaration statement e.g. Base base, *ptr = &base;. It's not possible to eliminate the two parts entirely, since both variables (base and ptr) have names. BTW - terms like "heap" and "stack" are not actually part of C++ (in this context) - heap and stack are specific concepts from some implementations (particular compilers and host systems) but not relevant to all implementations. — Peter
– Peter, Commented Nov 21, 2022 at 1:50
@NathanPierson This is just an example. But in the real case I think I would use it mostly to pass to a functions. — Nick
– Nick, Commented Nov 21, 2022 at 1:51
If you want to pass the address of a variable to a function, that variable must be declared before-hand. — Peter
– Peter, Commented Nov 21, 2022 at 1:52
You can just base &base to a function. You can write your function to take a reference and just pass base itself. That's why I asked about the actual use case, because it's not clear when you'd want this. — Nathan Pierson
– Nathan Pierson, Commented Nov 21, 2022 at 1:53

Maciej Polański · Accepted Answer · 2022-11-21 01:33:51Z

1

class Base {};

Base base, *ptr = &base;

But I wouldn't consider it "a well formatted code".

answered Nov 21, 2022 at 1:33

Maciej Polański

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1 Comment

Nick Over a year ago

Thanks a lot, got it! Then I'll be using 2 lines.

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