Why do I need to delete[]?

Question

Lets say I have a function like this:

int main()
{
    char* str = new char[10];

    for(int i=0;i<5;i++)
    {
        //Do stuff with str
    }

    d         


        

Answer 1

Another reason that I haven't see mentioned yet is to keep the output of static and dynamic analyzer tools (e.g. valgrind or Coverity) cleaner and quieter. Clean output with zero memory leaks or zero reported issues means that when a new one pops up it is easier to detect and fix.

You never know how your simple example will be used or evolved. Its better to start as clean and crisp as possible.

Answer 2

Most operating systems will reclaim memory upon process exit. Exceptions may include certain RTOS's, old mobile devices etc.

In an absolute sense your app won't leak memory; however it's good practice to clean up memory you allocate even if you know it won't cause a real leak. This issue is leaks are much, much harder to fix than not having them to begin with. Let's say you decide that you want to move the functionality in your main() to another function. You'll may end up with a real leak.

It's also bad aesthetics, many developers will look at the unfreed 'str' and feel slight nausea :(

Answer 3

Yes it is good practice. You should NEVER assume that your OS will take care of your memory deallocation, if you get into this habit, it will screw you later on.

To answer your question, however, upon exiting from the main, the OS frees all memory held by that process, so that includes any threads that you may have spawned or variables allocated. The OS will take care of freeing up that memory for others to use.

Answer 4

new and delete are reserved keyword brothers. They should cooperate with each other through a code block or through the parent object's lifecyle. Whenever the younger brother commits a fault (new), the older brother will want to to clean (delete) it up. Then the mother (your program) will be happy and proud of them.

Answer 5

Why would I need to delete str if I am going to end the program anyways?

Because you don't want to be lazy ...

I wouldn't care if that memory goes to a land full of unicorns if I am just going to exit, right?

Nope, I don't care about the land of unicorns either. The Land of Arwen is a different matter, Then we could cut their horns off and put them to good use(I've heard its a good aphrodisiac).

Is it just good practice?

It is justly a good practice.

Does it have deeper consequences?

Someone else has to clean up after you. Maybe you like that, I moved out from under my parents' roof many years ago.

Place a while(1) loop construct around your code without delete. The code-complexity does not matter. Memory leaks are related to process time.

From the perspective of debug, not releasing system resources(file handles, etc) can cause more significant and hard to find bugs. Memory-leaks while important are typically much easier to diagnose(why can't I write to this file?). Bad style will become more of a problem if you start working with threads.

int main()
{

    while(1)
    { 
        char* str = new char[10];

        for(int i=0;i<5;i++)
        {
            //Do stuff with str
        }
    }

    delete[] str;
    return 0;
}

Answer 6

Contrary answer: No, it is a waste of time. A program with a vast amount of allocated data would have to touch nearly every page in order to return all of the allocations to the free list. This wastes CPU time, creates memory pressure for uninteresting data, and possibly even causes the process to swap pages back in from disk. Simply exiting releases all of the memory back to the OS without any further action.

(not that I disagree with the reasons in "Yes", I just think there are arguments both ways)