Dangling Pointers are pointers that reference memory locations that have been freed or deleted within the program's memory space (memory that is no longer in use by the application). Dynamic Memory Allocation principles come into play when managing the allocation and deallocation of memory blocks. Functions like malloc, calloc, and free are commonly employed in C programming for the purpose of allocating and freeing memory blocks in dynamic memory management. The emergence of a Dangling Pointer is a consequence of using the free function to release a memory block.
If the content of this pointer is modified, it can lead to the overwriting of the system's instructions or program code, resulting in potential program crashes or unexpected outcomes. If we attempt to access a dangling pointer where the memory has been reassigned to another process, segmentation errors may occur.
How to Avoid Dangling Pointer Errors
Dangling pointer problems can be avoided by setting the pointer to NULL initially. By assigning the pointer a NULL value, it avoids pointing to deallocated memory. Setting a pointer to NULL signifies that it does not point to any specific memory location.
What are Void pointers?
Pointers lacking a specific data type are known as void pointers. As the name suggests, a void pointer indicates that it is essentially empty, allowing it to hold addresses of any data type within a program. Subsequently, these addresses stored in void pointers can be effortlessly converted into different data types through typecasting.
Such null pointers also simplify memory allocation. This is because they offer functions the necessary flexibility to allocate bytes and memory correctly.
Syntax:
It has the following syntax:
void *pinter_name;
In this scenario, the pointer type is denoted by the void keyword, succeeded by the pointer name that indicates the location of the address within the code and points to the pointer type. Upon declaring a pointer, both its type and name are specified, allowing it to accept data of any given type. To illustrate this concept, let's consider an example.
Example:
void *pt
In this scenario, the pointer requires a void type specifically, not an integer, floating-point number, or any other data type. Here, within the pLogic Practiceer, the * character is present, indicating the initialization of this pointer.
Advantages:
- Malloc and calloc return the void* type, allowing them to allocate memory of any data type.
- These pointers are used for building generic functions.
Key Differences between Dangling pointer and Void pointer:
There exist multiple variances between a Dangling pointer and a Void pointer. Below are some primary distinctions between these types of pointers:
| Aspect | Dangling Pointer | Void Pointer |
|---|---|---|
| Definition | Adangling pointeris a pointer that links to a memory region that has been set free, which causes undefined behavior whenever accessed. | Avoid pointeris a pointer that doesn't have an associated data type and is used to hold the address of any data type. |
| Cause | Produced when a pointer points to a memory location that has been deallocated or released. | Designed to contain any data type's address. |
| Purpose | It is typically occurs after releasing memory or when a pointer exits scope while it continues to be referenced. | It is used to develop generic functions or to manage memory dynamically without defining the data type. |
Risk |
It can cause software crashes, unusual activity, or security vulnerabilities if it is dereferenced or used after deallocation. | The main risk of using void pointers (void*) is that they can lead to type-related errors due to the lack of specific data types |
| Prevention | It can help to prevent unintentional use by setting the reference to NULL after deallocation. Avoid utilizing pointers after deallocation. | An explicit type cast is required to access the data pointed to by a void pointer. |
| Example: | A pointerptrreferring to memory released by thefree(ptr)method. Using ptr after free(ptr) produces in a dangling pointer. | void *ptr;is a void pointer that can hold the address of any data type. For example, ptr = &integer; or ptr = &character; holds addresses of the integer or type of character. |