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Table of contents
1.
Introduction
2.
What is Pointer in C?
3.
What is Wild Pointer in C? 
3.1.
Example of Wild Pointers
4.
Problems Caused by Wild Pointer in C
5.
How to Avoid Wild Pointer in C?
5.1.
1. A variable
5.2.
2. Memory management function (malloc, calloc, etc)
5.3.
NULL (null pointer)
6.
Drawbacks of Wild Pointer in C
7.
Frequently Asked Questions
7.1.
Why do wild pointers hold zero addresses and not garbage addresses?
7.2.
What is a void pointer in C?
7.3.
What is the size of a wild pointer in C?
8.
Conclusion
Last Updated: Mar 27, 2024
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Wild Pointer in C

Author Pallavi singh
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Data structures & algorithms (Beginner to Intermediate)
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Introduction

The pointers in the C programming language are variables that store another variable’s address. This variable can be of various types like char, int, function, array, or any other pointer.  The pointer in C language is declared using * (asterisk symbol).

wild pointer in c

These pointers are of various types. In this article, we will learn about the wild pointer in C language. We will also explore how to detect or prevent a wild pointer in C. So let’s get started with the article.

What is Pointer in C?

A pointer is a variable that can remember another variable's location. It is powerful because it works directly with memory. It is essential in C because they help to manage data flexibly and allows the creation of lists and manages memory efficiently. 

With pointers, you can also make functions that can change the original variables. It is a helpful tool that makes C programming more flexible and powerful.

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What is Wild Pointer in C? 

Any uninitialized pointer is known as a wild pointer in C because it points to some arbitrary memory location and can cause a program to crash or behave unexpectedly. A wild pointer in C is declared but not initialized. That is why, it points to any random memory location. 

Example of Wild Pointers

#include <stdio.h>
int main()
{
	int *ptr;   
	/* wild pointer */
	/* Random unknown memory location is being allocated. This should never be done. */
	*ptr = 12;
}


Note: If a pointer ptr points to any known variable then it is no longer a wild pointer in C. We can understand this better with the below example,

#include <stdio.h>
int main()
{
	int  *ptr;
	/* Ptr is a wild pointer in C */
	int a = 20;
	ptr = &a;  
	/* ptr is no longer a wild pointer */
	*ptr = 12;
	/* The value of a is modified */ 
	printf(“%d”, a);
}


Output

12

In the above code, we can see that initially “ptr” was a wild pointer because it was declared and not initialized but as soon as we assigned ptr to a known address, it was no longer a wild pointer.

You can also read about the dynamic arrays in c 

Problems Caused by Wild Pointer in C

A wild pointer in C language can lead to the following failures in our program:

  • Wild pointers can lead our program to crash during runtime.
  • Wild pointers can make our program behave unexpectedly because it may point to any unknown memory.
  • Wild pointers may point to a data value which has been deallocated. This may cause a runtime error in the code.

How to Avoid Wild Pointer in C?

To make our program error-free we must avoid wild pointers in our program. Avoiding wild pointers makes sure that our program will not cause any runtime or memory errors.

We can easily avoid the wild pointer in our program. To avoid this, we must initialize our pointer with some valid memory address at the time of declaration. We can initialize our pointer with the following things:

1. A variable

We can initialise our pointer with a valid variable’s address while declaring to prevent the wild pointer in C. 

For example:

#include <stdio.h>

int main()
{
	int a = 20;
	
	int  *ptr = &a;  
	/* ptr is now a valid pointer */
	
	*ptr = 12; 
	/* The value of a is modified */ 
	printf(“%d”, a);
}

 

Output:

12

 

In the above code, we have initialized the pointer ptr with a variable’s address. So, this will assure that our pointer is always initialized while declaration and hence, this will avoid the occurrence of wild pointer in our C program.

2. Memory management function (malloc, calloc, etc)

If we do not have a valid variable in our program or we do not want to point any of them, then we can use the memory management functions like malloc, calloc, etc. to assign a valid memory address. 

Let's see an example:

#include <stdio.h>


int main()
{
	int  *ptr = malloc(sizeof(int)); 
	 
	/* ptr points to a valid memory */
}

 

In the above code, we have initialized the pointer ptr with a memory management function malloc. So, this will assign a fixed memory to the pointer which will prevent it from pointing to a random or invalid address. Hence, the wild pointer is prevented.

NULL (null pointer)

Finally, if we don’t want to assign any memory address to the pointer while declaring. We must initialize the pointer with NULL (null pointer). 

Note: To avoid any kind of errors, we must validate if our pointer is a null pointer or not.

For example:

#include <stdio.h>

int main()
{
	int  *ptr = NULL;   
	
	/* null pointer */
	
	if(ptr == NULL) {
	
	/* Perform what to do on a null pointer */
	printf(“Under a NULL pointer block”);
	}
}


Output:

Under a NULL pointer block

For good practice implement it on C online compiler.

In the above example, the pointer ptr is initialized with a NULL value and hence it is not pointing to any random memory address.

Drawbacks of Wild Pointer in C

The drawbacks of Wild Pointer in C are:

  • Undefined Behavior: A wild pointer is a lost arrow without a clear target. When you try to use it in your program, things can go unpredictable, causing crashes or strange outcomes.
  • Memory Corruption: A wild pointer can unintentionally overwrite important data in the memory. This can lead to your program behaving strangely or becoming unstable.
  • Security Risks: Bad people, who want to harm, can use wild pointers to cause trouble in your program. They can create security problems and gain access to sensitive information.
  • Memory Leaks: If the wild pointer was used to keep track of a memory location that wasn't correctly released, it could result in memory leaks, meaning valuable memory is wasted.
  • Unreliable Program: Wild pointers can cause your program to behave strangely, making it difficult to trust and maintain. 

Frequently Asked Questions

Why do wild pointers hold zero addresses and not garbage addresses?

Since a wild pointer is uninitialised, hence its value is indeterminate and accessing its value will give undefined behaviour. Giving a printed value of zero.

What is a void pointer in C?

A void pointer is a specific type of pointer that points to some data location in the memory storage, which doesn’t have any specific type.

What is the size of a wild pointer in C?

The size of a wild pointer in C is determined by the system's data model, which can be 4 bytes in a 32-bit system and 8 bytes in a 64-bit system.
 

Conclusion

In this article, we understood wild pointers in the C programming language. We explored the errors that can be caused by a wild pointer in C in various cases. At last, we learned how to avoid Wild pointers in C programming language by various methods.

We hope this blog has helped you enhance your knowledge of the wild pointer in C. If you want to learn more, check out our articles VariablesConstants/Literals, and many more on our platform Coding Ninjas Studio.

Recommended Readings:

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