A handle leak is a type of

software bug A software bug is an error, flaw or fault in the design, development, or operation of computer software that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. The process of finding and correcting bugs i ...

that occurs when a

computer program A computer program is a sequence or set of instructions in a programming language for a computer to Execution (computing), execute. Computer programs are one component of software, which also includes software documentation, documentation and oth ...

asks for a handle to a

resource Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon thei ...

but does not free the handle when it is no longer used. If this occurs frequently or repeatedly over an extended period of time, a large number of handles may be marked in-use and thus unavailable, causing performance problems or a

crash Crash or CRASH may refer to: Common meanings * Collision, an impact between two or more objects * Crash (computing), a condition where a program ceases to respond * Cardiac arrest, a medical condition in which the heart stops beating * Couch ...

. The term is derived from

memory leak In computer science, a memory leak is a type of resource leak that occurs when a computer program incorrectly manages memory allocations in a way that memory which is no longer needed is not released. A memory leak may also happen when an object ...

. Handle leaks, like memory leaks, are specific instances of

resource leak In computer science, a resource leak is a particular type of resource consumption by a computer program where the program does not release resources it has acquired. This condition is normally the result of a bug in a program. Typical resource lea ...

Causes

One cause of a handle leak is when a programmer mistakenly believes that retrieving a handle to an entity is simply obtaining an unmanaged

reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a '' name'' ...

, without understanding that a count, a copy, or other operation is actually being performed. Another occurs because of poor

exception handling In computing and computer programming, exception handling is the process of responding to the occurrence of ''exceptions'' – anomalous or exceptional conditions requiring special processing – during the execution of a program. In general, an ...

design pattern A design pattern is the re-usable form of a solution to a design problem. The idea was introduced by the architect Christopher Alexander and has been adapted for various other disciplines, particularly software engineering. The "Gang of Four" boo ...

s when programmers do not consider that when an exception occurs and a sub routine is exited prematurely, the cleanup code at the end of the routine may not be executed. An example of this might be retrieving a handle to the display device. Programmers might use this handle to check some property (e.g. querying the supported resolutions), and then simply proceed on without ever releasing the handle. If the handle was just a pointer to some data structure with no additional management, then allowing the handle to pass out of scope would not cause an issue. However, in many cases, such handles must be explicitly closed or released to avoid leaking resources associated with them; the exact requirements for what must be done with a handle varies by interface.

References

Software bugs {{Compu-prog-stub