What is a Memory Leak and How to Solve It?

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.

How to Detect Memory Leak

Memory leaks can be very difficult to detect, as they rarely cause obvious error messages or symptoms. However, several ways can detect memory leaks, including:

• Observe memory usage by programs. This is the simplest, but also least accurate, way to detect memory leaks. Using tools like Task Manager on Windows, Activity Monitor on macOS, or Top on Linux, you can see how much memory a program is using. If memory usage continues to increase over time, with no significant decrease, then there is most likely a memory leak in the program.
• Use memory analysis tools. This is the most effective, but also the most complicated, way to detect memory leaks. Using a memory analysis tool, such as Valgrind, Visual Studio, or LeakCanary, we can see in detail how a program allocates and frees memory. Memory analysis tools can show how much memory is allocated, where it is allocated, who refers to it, and when it is freed. Memory analysis tools can also identify leaked memory and pinpoint the location of the code that caused the memory leak.
• Using automated testing tools. This is the most practical, but also the most expensive, way to detect memory leaks. Using automated testing tools, such as JUnit, Selenium, or Appium, we can run repetitive test scenarios and measure memory usage by programs. If memory usage continues to increase as the test scenario progresses, then there is most likely a memory leak in the program.

How to Overcome Memory Leak

Memory leaks can be very difficult to fix, as they usually require significant code changes and thorough testing. However, several ways can overcome memory leaks, including:

• Free up allocated memory. This is the most basic, but also the most important, way to deal with memory leaks. For each memory allocated by the program, make sure there is the memory that is freed up when it is no longer needed. Use functions like free () or delete for memory allocated with malloc() or new. Use features like try-with-resources or using for memory allocated with resources that need to be closed, such as files or network connections.
• Remove references to objects that are no longer needed. This is the most effective, but also the most difficult, way to deal with memory leaks. For each object referenced by the program, make sure there are no references left when the object is no longer needed. Use features such as weak references or soft references for objects that can be freed by the garbage collector if memory becomes scarce. Use features like nullify or clear to explicitly remove references to objects. Use features like unregister or remove to clean up listeners or callbacks you no longer need.
• Allocate memory as needed. This is the simplest, but also most useful, way to deal with memory leaks. For each memory allocated by the program, make sure it matches the program’s needs. Use features like resize or trim to resize the allocated memory according to the amount of data used. Use features such as cache or pool to manage frequently used and freed memory. Use features
• Terminate the problematic program or process, for example by using Task Manager, Activity Monitor, or top. Terminating the problematic program or process can free up memory allocated or leaked by that program or process so that it can be used by other programs or processes.
• Update the operating system, drivers, or applications, for example by using Windows Update, Software Update, or apt-get. Updating the operating system, drivers, or applications can fix bugs or errors that cause memory leaks, so that memory can be properly allocated and released by programs or processes.
• Change operating system settings, drivers, or applications, for example by using Control Panel, System Preferences, or configuration files. Changing operating system settings, drivers, or applications can optimize memory usage by programs or processes, so that memory can be allocated and released efficiently by programs or processes.
• Add physical or virtual memory, for example by installing additional RAM, or setting the size of the paging file or swap file. Adding physical or virtual memory can increase the memory capacity available in the system, so that memory can be allocated and released more easily by programs or processes.
• Use a memory optimization tool,  such as Memory Cleaner, RAMBooster, or CleanMem. Memory optimization tools can clean or free memory that is not used or leaked by programs or processes, so that memory can be used by other programs or processes.

Conclusion

Memory leak is a problem that can degrade system performance and stability. A memory leak occurs when a program or process allocates memory from the operating system but does not restore it when it is no longer needed. Memory leaks can be detected using resource monitors, memory analysis tools, or memory testing tools.

Memory leaks can be resolved by terminating problematic programs or processes, updating the operating system, drivers, or applications, changing operating system settings, drivers, or applications, adding physical or virtual memory, or using memory optimization tools. By overcoming memory leaks, we can improve system performance and stability.