Here, we will learn how to pass a string (character pointer) in a function, where function argument is void pointer. Your method of explanation is simple and interesting

I have working experience of different microcontrollers (stm32, LPC, PIC AVR and 8051), drivers (USB and virtual com-port), POS device (VeriFone) and payment gateway (global and first data). Although some compilers allow deleting a void pointer that points to dynamically allocated memory, doing so should be avoided, as it can result in undefined behavior. In this chapter we will be learning Dereferencing Void Pointer in C Programming. A pointer can be null. It would be incorrect, if we assign an address of a float variable to a pointer of type pointer to int.But void pointer is an exception to this rule.

– user529758 Jan 27 '12 at 22:38 It's not calling a function and casting its return value as void - that would require a couple more parentheses.

Un pointeur peut être null. In the last chapter we have learnt about void pointer.

Several respectful C programmers, for example Linus Torvalds, and enterprises such as GNU argue against this casting and call it bad practice as it decreases readability. According to C standard, the pointer to void shall have the same representation and alignment requirements as a pointer to a character type.The size of the pointers depending on the platform and it can be 2bytes, 4bytes or 8bytes …etc.Using the indirection operator (*) we can get back the value which is pointed by the pointer, but in case of void pointer we cannot use the indirection But what happened if we type-cast the void pointer, its working fine see the below example code.In the above code void pointer, pvData is pointing to the address of iData (integer variable). A pointer can be null. The void type of pointer is a special type of pointer. Before you dereference a void pointer it must be typecasted to appropriate pointer type.

It looks like an rvalue without an lvalue.

Is this just a no-op to prevent the function from being optimized away?

Here I am taking one of the most popular applications of the void pointer in qsort function.A qsort is a C standard library function that is used to sort arrays. If you will directly perform an arithmetic operation on the void pointer you may get unexpected results.

(void)(foo); It's not a void pointer cast - that would be straightforward. So to access the value of integer variable (iData) through the void pointer we have to typecast void pointer through the integer pointer.Now above expression behave like an integer pointer. Consider the given example # include < stdio.h > //function prototype void printString (void * ptr); int main {char * str = " Hi, there!

So you should perform proper typecasting on the void pointer before performing the arithmetic operation.When you will run the above code you will get the unexpected result.Since the array (aiData) is the collection of integer element so the type of &aiData[0] would be a pointer to int (int*). [/box] Why it is necessary to use Void Pointer ? It is not possible to do pointer arithmetic on a void pointer. Toutefois, vous pouvez utiliser un cast pour convertir un pointeur void en n'importe quel autre type pointeur, et inversement. I am an embedded c software engineer and a corporate trainer, currently, I am working as senior software engineer in a largest Software consulting company . In my case, the integer size is 4 byte.Application of void pointers are very wide, we can not cover all the application in one article. According to C standard, the The size of a void pointer is similar to the size of the character pointer. The following program demonstrates pointer arithmetic in void pointers.The void pointers are used extensively in dynamic memory allocation which we will discuss next.// wrong since type of fp is pointer to float A void pointer can point to a variable of any data type. If you are new in c programming, you should read this article “C pointer concept“. In this article, we will learn what is void pointer in C and how we can use void pointer in our C code.

This is because pointer arithmetic requires the pointer to know what size object it is pointing to, so it can increment or decrement the pointer appropriately. You cannot apply the indirection operator to a pointer of type void*.

We have learned in chapter Pointer Basics in C that if a pointer is of type pointer to int or (int *) then it can hold the address of the variable of type int only. Reason 1 : Re-usability of Pointer Using the void pointer we can store the address of any object and whenever required we can get back the object through the indirection operator with proper casting.You can see in the example code, how a single pointer is dealing with different types of variables. Passing pointers between methods can cause undefined behavior.

You already know how to dereference an integer pointer using an indirection operator (*).Now you will get the value of the integer which addresses pointed by the void pointer.A very important feature of the void pointer is reusability. Before you apply pointer arithmetic in void pointers make sure to provide a proper typecast first otherwise you may get unexcepted results. Using the qsort function, we can sort the array of integer, double, long, etc.void qsort(void *arr, size_t elements, size_t size, int (*comp)(const void *, const void*));In this example code, I am showing how is the qsort function sort any type of array with the help of compare function.But with proper typecasting, we can dereference the void pointer and get back the value of the pointed address.You can see how memcpy is working here as a generic copy function with the help of a void pointer.Great article with an in-depth insight into the usage of void pointers.