Definition
A dangling pointer is an object that stores a memory address of a memory location that has been freed or invalidated, resulting in an unpredictable state or invalid state. Also, since the memory location is invalid, accessing the pointer can cause the program to behave unpredictably.
Causes of Dangling Pointers
- Incorrect deallocation: Dangling pointers can be created when a programmer frees a memory without updating the corresponding pointers.
- Premature deallocation: Releasing a memory location before the system is done with it can cause dangling pointers.
- Returning local variables: When a function completes running, all the local variables are deleted. A dangling variable can occur when the pointer refers to a local variable.
Dangling Pointer Issues
- Security vulnerabilities: Attackers can exploit dangling pointers to execute arbitrary code or gain unauthorized access.
- Unexpected behavior: Dangling pointers confuse the system, leading to unpredictable behavior. Such code is also difficult to debug.
- Accessing disabled memory: Dangling pointers may lead to system crashes or corrupt data when the system tries to write or read to disabled memory locations.
Preventing Dangling Pointers
- Use automatic memory management to deallocate memory and minimize the risk of dangling pointers.
- Update pointers with a NULL value after deallocating the corresponding memory locations.
- Employ proper memory management to ensure your system deallocates memory only when it is no longer needed and update all pointers accordingly.