Re: Why use new?
saneman wrote:
In the below code I make 2 instances of the class Bob. The first
instance does not use new (automatic allocation?) and the second
instance is used with new (dynamic allocation?)
#include<iostream>
class Bob {
public:
Bob(int a): n(a) {}
int getn() {
return n;
}
private:
int n;
};
int main() {
Bob b1(22);
printf("n = %d\n", b1.getn());
Bob* b2 = new Bob(88);
printf("n = %d\n", b2->getn());
return 0;
}
But when are there any reason to use new?
What does your favourite C++ book say about the use of dynamic memory?
Read up on lifetime of objects. To hint: there are three "lifetimes"
(they are called "storage duration" in C++): automatic, static, and
dynamic.
And will the b2 pointer automatically be deallocated when main
returns?
No, it will not. It may or may not be deallocated by the hosting
environment when the program finishes. Most modern operating systems
do deallocate all memory used by the process when the process closes
and returns control to the OS.
V
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