`new` vs. Non-`new` Object Instantiation: What are the Key Functional Differences?

Instantiating Objects: 'new' vs. Non-'new'

Aside from memory allocation, what functional differences exist between the following lines of code?

Time t (12, 0, 0); //t is a Time object

Time* t = new Time(12, 0, 0);//t is a pointer to a dynamically allocated Time object

Non-'new' Instantiation

The first line, Time t (12, 0, 0);, creates a variable t of type Time in local scope. This variable is typically allocated on the stack and will be destroyed at the end of its scope.

'new' Instantiation

In contrast, the second line, Time* t = new Time(12, 0, 0);, allocates a block of memory on the heap (typically) via the ::operator new() or Time::operator new() functions. This memory block is then initialized using the Time::Time() constructor, with the address of the newly allocated memory set as the this pointer. The pointer to the allocated memory is stored in the variable t.

Other Differences

While the primary difference lies in memory allocation, there are a few other subtle distinctions:

• Lifetime: Non-'new' objects have automatic storage duration, meaning they are destroyed automatically when their scope ends. 'new' objects, on the other hand, have dynamic storage duration and must be explicitly deleted to reclaim their memory.
• Scoping: Non-'new' objects are defined and exist within their local scope. 'new' objects are allocated outside the program's stack and are not confined to any specific scope.
• Ownership: The memory for 'new' objects must be managed explicitly, and the related pointers must be dereferenced safely. Non-'new' objects are automatically managed by the compiler, so there is no need for explicit memory cleanup.

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