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Pointers in C++
2023-03-10 18:02:32

Pointers in C++

Pointers are a powerful feature in the C++ programming language, allowing developers to directly manipulate memory addresses and create more efficient and dynamic programs. However, pointers can also source various problems and bugs, especially for beginner programmers. Here are some common pointer-related issues in C++ and how to avoid them:

  • Null pointers: A null pointer is a special type that points to address 0 in memory, indicating that it is not pointing to a valid memory location. Accessing a null pointer can cause a runtime error or segmentation fault, as the program will try to access an invalid memory location. To avoid this, you should always check if a pointer is null before dereferencing it or using it to access an object.
  • Dangling pointers: A dangling pointer is a pointer that points to a memory location that has been deallocated or freed. Dereferencing a dangling pointer can lead to undefined behaviour or a segmentation fault. To avoid this, you should always ensure that a pointer points to a valid memory location before using it and avoid storing pointers to objects that have already been deleted or freed.
  • Memory leaks: A memory leak occurs when a program dynamically allocates memory but fails to deallocate it when it is no longer needed. This can lead to a depletion of available memory and, ultimately, program failure. To avoid memory leaks, using the delete or free function, you should always deallocate dynamically allocated memory when it is no longer needed.
  • Wild pointers: A wild pointer is a pointer that has not been initialized or assigned a valid memory address. Dereferencing a wild pointer can lead to undefined behaviour or a segmentation fault. To avoid this, you should always initialize pointers with a valid memory address or assign them to a valid object before using them.

By being aware of these common pointer-related issues and taking steps to prevent them, you can write more stable and efficient C++ programs.

Addresses can be represented in a symbolic way using pointers. They allow programs to create and manipulate dynamic data structures and simulate call-by-reference. One of the most common uses for pointers is iterating over elements in arrays or other data structures.

The pointer variable, which points to the same data type (such as an int or string), is given the address of the variable you are working with.

What are Pointers?

Assign a pointer to the address of a variable using the unary operator (&), which returns the address of the variable. Access the value contained in the address using the unary operator (*), which returns the variable’s value at the position specified bythe operand. We associate data types with pointers because we know how many bytes the data is stored in. When a pointer is incremented, it increases by the size of the data type it points to.

// C++ program to illustrate Pointers
#include <bits/stdc++.h>
using namespace std;
void geeks()
{
    int var = 20;  
    // declare pointer variable
    int* ptr;
    // note that data type of ptr and var must be same
ptr = &var;
    // assign the address of a variable to a pointer
cout<< "Value at ptr = " <<ptr<< "\n";
cout<< "Value at var = " << var << "\n";
cout<< "Value at *ptr = " << *ptr<< "\n";
}
// Driver program
int main() 
{ 
  geeks(); 
  return 0;
}

Output:

Value at ptr = 0x7ffe454c08cc
Value at var = 20
Value at *ptr = 20

Array name as a pointer Array name serve as constant pointers and contains the address of the first array element. This implies that the location put away in the cluster name can't be changed. For instance, assuming you have an exhibit named val, you can utilize val and &val[0] reciprocally.

  • Pointers have advantages in terms of performance and code reduction Strings, trees, arrays, structs, and functions can all be retrieved using them
  • Functions can return multiple values thanks to pointers
  • Similarly, pointers let you navigate to memory locations in your PC's memory
  • When working with pointers for the first time, beginners frequently make the mistake of working with undefined behaviour. It's simple to explain. However, avoiding them may not always be as straightforward as it may appear.
  • Let's say we release shared memory using one of two pointers that point to the same memory address. What takes place with the second one? If we use malloc, it will point to a previously released address that can be reallocated.