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A null pointer is usually represented as a pointer to address 0 in the address space; many operating systems set up the MMU to indicate that the page that contains that address is not in memory, and do not include that page in the virtual address space, so that attempts to read or write the memory referenced by a null pointer get an invalid ...
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference.An object referenced only by weak references – meaning "every chain of references that reaches the object includes at least one weak reference as a link" – is considered weakly reachable, and can be treated as unreachable and ...
In computer science, a memory leak is a type of resource leak that occurs when a computer program incorrectly manages memory allocations [1] in a way that memory which is no longer needed is not released. A memory leak may also happen when an object is stored in memory but cannot be accessed by the running code (i.e. unreachable memory). [2]
If the computer runs out of both memory and swap space, the OS might automatically reboot — or even worse hang. [15] Programs written in programming languages that use a garbage collector (e.g. Java) are less prone to memory leaks, since memory that is no longer referenced will be freed up by the garbage collector. This however does not mean ...
At the hardware level, the fault is initially raised by the memory management unit (MMU) on illegal access (if the referenced memory exists), as part of its memory protection feature, or an invalid page fault (if the referenced memory does not exist). If the problem is not an invalid logical address but instead an invalid physical address, a ...
In many languages (e.g., the C programming language) deleting an object from memory explicitly or by destroying the stack frame on return does not alter associated pointers. The pointer still points to the same location in memory even though that location may now be used for other purposes. A straightforward example is shown below:
In computer science, thrashing occurs in a system with virtual memory when a computer's real storage resources are overcommitted, leading to a constant state of paging and page faults, slowing most application-level processing. [1] This causes the performance of the computer to degrade or even collapse. The situation can continue indefinitely ...
Using non-owned memory: It is common to use pointers to access and modify memory. If such a pointer is a null pointer, dangling pointer (pointing to memory that has already been freed), or to a memory location outside of current stack or heap bounds, it is referring to memory that is not then possessed by the program. Using such pointers is a ...