Question

I would like to know what are the common memory management issues associated with C and C++. How can we debug these errors.

Here are few i know

1)uninitialized variable use

2)delete a pointer two times

3)writing array out of bounds

4)failing to deallocate memory

5)race conditions

1) malloc passed back a NULL pointer. You need to cast this pointer to whatever you want.

2) for string, need to allocate an extra byte for the end character.

3) double pointers.

4) (delete and malloc) and (free and new) don’t go together

5) see what the actual function returns (return code) on failure and free the memory if it fails.
6) check for size allocating memory malloc(func +1)

7) check how u pass the double pointe **ptr to function

8) check for data size for behaviour undefined function call

9) failure of allocation of memory

Answer 1

Preemptively preventing these errors in the first place:

1) Turn warnings to error levels to overcome the uninitialized errors. Compilers will frequently issue such warnings and by having them accessed as errors you’ll be forced to fix the problem.

2) Use Smart pointers. You can find a good versions of such things in Boost.

3) Use vectors or other STL containers. Don’t use arrays unless you’re using one of the Boost variety.

4) Again, use a container object or smart pointer to handle this issue for you.

5) Use immutable data structures everywhere you can and place locks around modification points for shared mutable objects.

Dealing with legacy applications

1) Same as above.

2) Use integration tests to see how different components of your application play out. This should find many cases of such errors. Seriously consider having a formal peer review done by another group writing a different segment of the application who would come into contact with your naked pointers.

3) You can overload the new operator so that it allocates one extra byte before and after an object. These bytes should then be filled with some easily identifiable value such as 0xDEADBEEF. All you then have to do is check the preceeding byte before and after to witness if and when your memory is being corrupted by such errors.

4) Track your memory usage by running various components of your application many times. If your memory grows, check for missing deallocations.

5) Good luck. Sorry, but this is one of those things that can work 99.9% of the time and then, boom! The customer complains.