Software

Things You'll Need

Proficiency in C++
C++ compiler
Debugger and other investigative software tools
1
Understand the operator basics. The C++ operator "new" allocates heap memory. The "delete" operator frees heap memory. For every "new," you should use a "delete" so that you free the same memory you allocated:

char* str = new char [30]; // Allocate 30 bytes to house a string.

delete [] str; // Clear those 30 bytes and make str point nowhere.
2
Reallocate memory only if you've deleted. In the code below, str acquires a new address with the second allocation. The first address is lost irretrievably, and so are the 30 bytes that it pointed to. Now they're impossible to free, and you have a memory leak:

char* str = new char [30]; // Give str a memory address.

// delete [] str; // Remove the first comment marking in this line to correct.

str = new char [60]; /* Give str another memory address with
the first one gone forever.*/

delete [] str; // This deletes the 60 bytes, not just the first 30.
3
Watch those pointer assignments. Every dynamic variable (allocated memory on the heap) needs to be associated with a pointer. When a dynamic variable becomes disassociated from its pointer(s), it becomes impossible to erase. Again, this results in a memory leak:

char* str1 = new char [30];

char* str2 = new char [40];

strcpy(str1, "Memory leak");

str2 = str1; // Bad! Now the 40 bytes are impossible to free.

delete [] str2; // This deletes the 30 bytes.

delete [] str1; // Possible access violation. What a disaster!
4
Be careful with local pointers. A pointer you declare in a function is allocated on the stack, but the dynamic variable it points to is allocated on the heap. If you don't delete it, it will persist after the program exits from the function:

void Leak(int x){

char* p = new char [x];

// delete [] p; // Remove the first comment marking to correct.

}
5
Pay attention to the square braces after "delete." Use "delete" by itself to free a single object. Use "delete" [] with square brackets to free a heap array. Don't do something like this:

char* one = new char;

delete [] one; // Wrong

char* many = new char [30];

delete many; // Wrong!
6
If the leak yet allowed - I'm usually seeking it with deleaker. - Robert Miles 11 years ago

Grete!!
Most the code I've worked on (which is in C and at three different companies) uses a standard format to reduce the chances of memory leaks. The form involves:
1. Free memory at the same level of the function heiarchy it was allocated in.
a. If you have a create function, then have a delete.
b. If CreateFoo, calls CreateBar, then have a DeleteFoo that calls DeleteBar.
2. If an error happens in a function, free all memory allocated by that function before returning. [see example]
a. If the erorr happens in CreateFoo, try to use DeleteFoo to do the cleanup. Or a helper function that is also used by DeleteFoo.
b. Use separate variables for the local object creation from the pointers used to return an object.
3. Make all the error handling in each function as similar to other functions as possible. - Bazylio 11 years ago

Wow! It is a complete guide! - gromret 11 years ago

Good advices, but they dont always work. Sometimes it is necessary to use a third-party debugging methods to detect errors. - MastAvalons 10 years ago

I'm afraid that's a little beyond my abilities to answer. Its been a long time since I took my c++ classes in college (well... 2 years, but... that's a long time for a teenager :). I'd recommend looking around in this forum: http://stackoverflow.com/. It's more oriented towards programming and you'd probably find more help there. I would definitely do some searching and reading before posting.. - Ben M 11 years ago

Thanks for the link. I am not acquainted with this resource - gromret 11 years ago