Proper Usage of the delete Operator

thetinman · 04-24-2007, 02:55 PM

I have two questions about the delete operator.

1.) Can I delete multiple variables with a single call to delete? What I mean is, can I do the following:

Code:

double *a, *b, *c;

a = new double[10];
b = new double[10];
c = new double[10];

delete [] a, b, c;

???

2.) Is it ever ok to ommit the delete operator? For instance, if I have a function that created some dynamically allocated objects, and that functions is about to return, should my program end with the following:

Code:

	delete [] a;
	delete [] b;
	delete [] c;

	return 0;
}

Or could I ommit the delete oporator and end the function merely by coding:

Code:

	return 0;
}

???

**laserlight** · 04-24-2007, 03:01 PM

Quote:

Can I delete multiple variables with a single call to delete?

I do not think so, since delete[] only takes one expression.

Quote:

Is it ever ok to ommit the delete operator?

The rule of thumb is: whatever you new, remember to delete; whatever you new[], remember to delete[].

From what I understand (or do not understand, heheh), the operating system may be able to reclaim undeleted resources after program execution ends. On the other hand, by following the rule I outlined, you ensure that there are no memory leaks even if no such resource reclamation is done.

**CornedBee** · 04-24-2007, 03:07 PM

Quote:

2.) Is it ever ok to ommit the delete operator?

Yes. When you're
a) using a smart pointer (but then the delete operator is merely hidden inside the smart pointer) or
b) using garbage collections. You aren't.

Daved · 04-24-2007, 04:28 PM

In some rare cases it is probably acceptable to delete global objects if you have some dependency issues and the destructor is trivial.

However, in C++ there are very few times when you want to use dynamic arrays like that. A vector is probably much better, and you don't have to worry about memory management in this way.

**CornedBee** · 04-25-2007, 05:10 AM

Quote:

Originally Posted by Daved

In some rare cases it is probably acceptable to delete global objects

Either I'm misunderstanding what you mean, or this is plain wrong. What do you mean by "global objects"?

Daved · 04-25-2007, 12:49 PM

I meant it is acceptable to not delete global objects. Although global objects is probably the wrong term. I'm talking about things like singletons whose lifetimes outlast main(). In some cases it is probably acceptable to not clean them up since the program is terminating anyway.

**CornedBee** · 04-25-2007, 01:20 PM

Yes, memory is reclaimed. But if the singletons hold anything that outlives a process (I believe shared memory in POSIX does, for example), they need to free that.

Hussain Hani · 04-25-2007, 11:53 PM

Quote:

Or could I ommit the delete oporator and end the function merely by coding:

Code:

return 0;

C++ doesnt have garbage collection, so dont wait for the "return" to end the whole program

04-24-2007, 02:55 PM	#1
thetinman Registered User Join Date: Aug 2005 Posts: 180	Proper Usage of the delete Operator I have two questions about the delete operator. 1.) Can I delete multiple variables with a single call to delete? What I mean is, can I do the following: Code: double a, b, *c; a = new double[10]; b = new double[10]; c = new double[10]; delete [] a, b, c; ??? 2.) Is it ever ok to ommit the delete operator? For instance, if I have a function that created some dynamically allocated objects, and that functions is about to return, should my program end with the following: Code: delete [] a; delete [] b; delete [] c; return 0; } Or could I ommit the delete oporator and end the function merely by coding: Code: return 0; } ???
thetinman is offline

04-24-2007, 04:28 PM	#4
Daved Registered User Join Date: Jan 2005 Posts: 7,137	In some rare cases it is probably acceptable to delete global objects if you have some dependency issues and the destructor is trivial. However, in C++ there are very few times when you want to use dynamic arrays like that. A vector is probably much better, and you don't have to worry about memory management in this way.
Daved is offline

04-25-2007, 12:49 PM	#6
Daved Registered User Join Date: Jan 2005 Posts: 7,137	I meant it is acceptable to not delete global objects. Although global objects is probably the wrong term. I'm talking about things like singletons whose lifetimes outlast main(). In some cases it is probably acceptable to not clean them up since the program is terminating anyway.
Daved is offline

04-25-2007, 01:20 PM	#7
CornedBee Cat without Hat Join Date: Apr 2003 Posts: 8,439	Yes, memory is reclaimed. But if the singletons hold anything that outlives a process (I believe shared memory in POSIX does, for example), they need to free that. __________________ All the buzzt! CornedBee "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code." - Flon's Law
CornedBee is offline

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
C++ Operator Overloading help	Bartosz	C++ Programming	2	08-17-2005 12:55 PM
private overloading of new & delete	Aidman	C++ Programming	12	04-28-2005 01:11 PM
operator overloading and dynamic memory program	jlmac2001	C++ Programming	3	04-06-2003 11:51 PM
Finishing my "int class"... help with weird operator overloads	Trauts	C++ Programming	3	12-06-2002 10:02 AM
int vs BIG INT	rumi_red	C++ Programming	1	10-30-2001 04:15 AM