Memory leak is one of the problems often faced by software developers, especially those who use programming languages such as C and C ++.
Memory leaks occur when a program allocates memory from a heap but does not free it when it is no longer needed. As a result, the memory in the system becomes reduced over time, leading to decreased performance and even application failures.
Memory leaks can be very difficult to detect and fix, as they rarely cause obvious error messages or symptoms. However, if left unchecked, memory leaks can cause significant negative impacts on users and systems.
Therefore, developers need to understand what a memory leak is, what causes it, how to detect it, and how to overcome it.
Causes of Memory Leak
Memory leaks can be caused by a variety of factors, but are generally related to errors in memory management by programs. Some common causes of memory leaks are:
- Forgetting to free up allocated memory. This is the most common error, especially in programming languages that do not have garbage collection features, such as C and C++. If a program allocates memory with functions such as malloc() or new, it must free up that memory with functions such as free() or delete when it is no longer needed. If not, then the memory will remain allocated and cannot be used by other programs.
- Store references to objects that are no longer needed. This is a common error in programming languages that feature garbage collections, such as Java and C#. Garbage collection is a mechanism that automatically frees memory that is no longer referenced by the program. However, if a program still stores references to objects that are no longer needed, then the garbage collector cannot free up that memory. For example, if a program stores a reference to a closed Activity or Fragment, then the resources used by that Activity or Fragment cannot be freed.
- Allocate more memory than needed. This is an error that can occur in all programming languages, especially those that use dynamic data types, such as arrays or strings. If a program allocates more memory than needed, then the memory will be wasted and cannot be used by other programs. For example, if a program allocates an array of 100 in size, but uses only 10 elements, then the remaining 90 elements will consume useless memory.
- Misusing singletons and global objects. Singleton is a design pattern that ensures that only one instance of a class can be accessed by the program. A global object is an object that can be accessed by all parts of the program. Both types of objects can cause memory leaks if they store references to other objects that have shorter life cycles. For example, if a singleton or global object stores a reference to a Context of an Activity, then that Activity cannot be released by the garbage collector even if it is closed.
- Register listeners and callbacks without cleaning them up. Listeners and callbacks are mechanisms that allow a program to respond to events or outcomes of other operations. Listeners and callbacks typically accept objects as parameters, which can store references to other objects. If a program registers a listener or callback without cleaning it when it is no longer needed, then the object referenced by that listener or callback cannot be freed by the garbage collector.