void pointer is an approach towards generic functions and generic programming in C. Note: Writing programs without being constrained by data type is known as generic programming. Note that the above program compiles in C, but doesn’t compile in C++. This doesn't generate any code whatsoever. Join our social networks below and stay updated with latest contests, videos, internships and jobs! C++ void pointer is used to store the address of any other data type. View Answer. Sanfoundry Global Education & Learning Series – C++ Programming Language. b) 6 // … Functions that do not return a value Most commonly, void is used to indicate that a function does not return a value: It's perhaps too harsh a judgement of C, but certainly oneof the reasons the language was invented was to write operatingsystems. The void pointer can point to which type of objects? GitHub Gist: instantly share code, notes, ... You can’t perform that action at this time. If you're going to master C, you need to understand pointerarithmetic, and in particular, th… Our C++ programming questions come with the detailed explanation of the answers which helps in better understanding of C++ concepts. Please use ide.geeksforgeeks.org, A void pointer is a pointer that has no associated data type with it. Answer: a Explanation: Because the void pointer is used to cast the variables only, So pointer arithmetic can’t be done in a void pointer. However, in GNU C it is allowed by considering the size of void is 1. It is also called general purpose pointer. It can be reused to point at any data type we want to. Would be better off providing overloaded functions for each type of parameter that can be accepted. 9. b) two memory addresses 5. Passing by pointer Vs Passing by Reference in C++, Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. The outer star on the left actually tells the compiler to dereference the thing on the right. c) memory address Writing such code requires the ability to accessaddresses in memory in an efficient manner. The pointer can point to any variable that is not declared with which of these? View Answer, 3. There is no way the compiler can know (or guess?) Void Pointers & Malloc & Free Sample. Note that we can store any data type in void pointer, but, when we want to retrieve data from void pointer then we need to type cast to the specific data type. b) 8.14 d) using shift keyword 8. void value; // won't work, variables can't be defined with a void type Void is typically used in several different contexts. The function pointer syntax can be cumbersome, particularly in complex cases like nested function pointers. Answers: pointer arithemetic. d) runtime error This is because a void pointer has no data type associated with it. One shall practice these questions to improve their C++ programming skills needed for various interviews (campus interviews, walk-in interviews, company interviews), placements, entrance exams and other competitive exams. Void pointers do one thing and one thing only: store an address. close, link © 2011-2020 Sanfoundry. A generic function is a special function that focuses on logic without confining to data type. share | improve this answer | follow | 2) The C standard doesn’t allow pointer arithmetic with void pointers. b) address of string “abcdefghij” b) volatile Dereferencing a void pointer in C 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 operator directly. Original code: The *'s in the cast itself don't do anything besides tell the compiler what type of thing the void pointer is supposed to be. what type of data is pointed to by the void pointer. But you can do it somehow. Recommended Articles. What will be the output of the following C++ code? What will be the output of the following C++ code? *( int* ) ( randomData + 10 ) = ( int) 323453 //323453 can be an int variable aswell Im not sure if this is the right way to do perform a dereference. This is because a void pointer has no data type that creates a problem for the compiler to predict the size of the pointed object. View Answer. Submit Next question -> a) 2d What we can’t do on a void pointer? What we can’t do on a void pointer? All Rights Reserved. Finally, void pointers. In below program, we have created a void pointer and assign the address of int variable. It is declared like this: void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. c) compile time error 6. 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." a) int generate link and share the link here. For example the following program doesn’t compile. It automatically converts to and from other pointer types without needing a cast, so pointers to void are usually preferable over pointers … I'm still think about some safe conversion of that pointers and wrote little code that make some conversions using void pointer and return void from function. You signed in with another tab or window. View Answer, 10. //The raw pointer is void* auto vp = std::shared_ptr (new int ()); //OK //However, we can't do much with 'vp' //Another example //Inheritance with no virtual destructor struct A {//stuff.. ~A() { std::cout << "~A\n"; } //not virtual}; struct B : A {//stuff.. ~B() { std::cout << "~B\n"; } //not virtual}; //shared_ptr managing a B object //raw pointer is A* and managed pointer is B* auto pa = std::shared_ptr(new … Difference between "int main()" and "int main(void)" in C/C++? In addition, because we assign a value to temp in the above code, we must know what data types first and second point to, so the compiler knows how to make the assignment. For a start, if you want a pointer to that structure, why don't you just define it as a pointer to that structure: testStructure *ptr; The type given for a variable in its declation or definition is fixed; if you declare ptr as a pointer to void, then it will always be a pointer to void. b) class member in c++ Dereferencing a void Pointer # We can't just dereference a void pointer using indirection ( * ) operator. A generic pointer can be assigned a pointer value of any type, but it may not be dereferenced. Participate in the Sanfoundry Certification contest to get free Certificate of Merit. d) none of the mentioned In my work as a graduate student, I build distributed data structures, and having a remote pointer abstraction is an essential tool for me to write clean, correct code. Void Pointers. Instead what is exchanged are pointers to values. One option that was explored was emitting such a pointer as mod_req(Func) void*. 1) void pointers cannot be dereferenced. d) 12 This section on C++ programming questions and answers focuses on “Pointer to Void”. 1) malloc() and calloc() return void * type and this allows these functions to be used to allocate memory of any data type (just because of void *). What will be the output of the following C++ code? brightness_4 acknowledge that you have read and understood our, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, An Uncommon representation of array elements, Delete a Linked List node at a given position, Find Length of a Linked List (Iterative and Recursive), Search an element in a Linked List (Iterative and Recursive), Write a function to get Nth node in a Linked List, Program for n’th node from the end of a Linked List, Find the middle of a given linked list in C and Java, Write a function that counts the number of times a given int occurs in a Linked List, Add two numbers represented by linked lists | Set 1, Add two numbers represented by linked lists | Set 2, Add Two Numbers Represented by Linked Lists | Set 3, compare function which is used in qsort(), http://stackoverflow.com/questions/20967868/should-the-compiler-warn-on-pointer-arithmetic-with-a-void-pointer, http://stackoverflow.com/questions/692564/concept-of-void-pointer-in-c-programming, Find next greater number with same set of digits, Dynamic Memory Allocation in C using malloc(), calloc(), free() and realloc(), Left Shift and Right Shift Operators in C/C++, Rounding Floating Point Number To two Decimal Places in C and C++, INT_MAX and INT_MIN in C/C++ and Applications, Write Interview pointer arithemetic pointer functions both of the mentioned none of the mentioned. They're also a bigreason programmers have bugs. b) when it cast to another type of object a) 8, memory address Im not sure how to do this. code, Advantages of void pointers: How will the function know the type of pointer being passed and how to handle it given it comes through as a void *. Since we cannot dereference a void pointer, we cannot use *ptr.. void pointer in C / C++. c) both const & volatile View Answer. View Answer, 4. A void pointer can point to a variable of any data type and void pointer can be assigned to a pointer of any type. d) 4d All pointers, regardless of pointee, are 8-byte addresses that are type-compatible with void*. both of the mentioned. edit d) all of the mentioned d) pointer functions & objects Here is a listing of C++ programming questions on “Pointer to Void” along with answers, explanations and/or solutions: 1. With their flexibility, void pointers also bring some constraints. A directory of Objective Type Questions covering all the Computer Science subjects. What will be the output of the following C++ code? a) abcdefghij c) 3d A void pointer can hold address of any type and can be typcasted to any type. In C, malloc () and calloc () functions return void * or generic pointers. b) no output However, if we convert the void* pointer type to the float* type, we can use the value pointed to by the void pointer.. Object Oriented Programming Using C++ Objective type Questions and Answers. Experience. View Answer, 2. c) double This is why pointersare such an important part of the C language. Unfortunately, the C++ type system is not yet aware of null-checks (A “flow” type system), so we must use our own human hearts and hands to ensure we do these checks. b) float They can be a beginner, fresher, engineering graduate or an experienced IT professional. http://stackoverflow.com/questions/20967868/should-the-compiler-warn-on-pointer-arithmetic-with-a-void-pointer a) when it doesn’t point to any value Writing code in comment? These questions can be attempted by anyone focusing on learning C++ programming language. References: This doesn't work though as a mod_req cannot bind to a TypeSpec and hence cannot target generic instantiations. Note that the above program may not work in other compilers. But in the case of a void pointer we need to typecast the pointer variable to dereference it. For example the following program compiles and runs fine in gcc. For instance, I need to call a function which > returns a status, as follows: > > > status = EST_WriteTargetRegister (long handle, Unsign int register, > void * value) > > > How do I pass the "void * value" to the input of a Call Library > FUnction Node. Output. A void pointer is just like any other pointer, except that it does not know what type it points to. a) pointer arithmetic Noncompliant Code Example. View Answer. b) pointer functions d) runtime error Some Interesting Facts: What will be the output of the following C++ code? a) methods in c++ void pointers just store an address, they have no type, so when you try to dereference them, the compiler doesn''t know what to do. Agreed, OP's method doesn't make much sense. then is static_cast conversion to needed format. Don’t stop learning now. c) compile time error a) 5 Basically the type of data that it points to is can be any. Attention reader! Void pointer is declared with void*. The void pointer in C is a pointer which is not associated with any data types. You can't do it directly. It points to some data location in the storage means points to the address of variables. "It is not possible to do pointer arithmetic on a void pointer. Void Pointer Example. A void pointer can hold address of any type and can be typcasted to any type. While we can certainly specify parameters that are void * parameters, we cannot dereference a void pointer without knowing the data type to which it points. c) using delete keyword a) equal Dereference the typed pointer to access the value. This program prints the value of the address pointed to by the void pointer ptr.. View Answer. It is pretty much a similar situation with dereferencing a void pointer. By creating an API that returns and accepts smart pointers, you are introducing nullability where it is not appropriate. When does the void pointer can be dereferenced? The keyword void is used as the return type of a function not returning a value and to indicate an empty argument list to a function. By using our site, you Cast to appropriate pointer type and do arithmetic on it. Void pointer is also known as generic pointer in c and c++ programs. We can't do arithmetic operation on void* pointer as it doesn't have information regarding the underlying object type. I was think about that void, because it can … We can’t dereference the void pointer without reassigning this pointer to another variable type. Void pointers are useful when you … Void pointer is a specific pointer type – void * – a pointer that points to some data location in storage, which doesn’t have any specific type. That pointer type has valid uses, but this isn't one of them. http://stackoverflow.com/questions/692564/concept-of-void-pointer-in-c-programming, Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. d) runtime error The content of pointer is 2.3. c) methods & class member in c++ This is an overview of what has to be done:-The pointer has to be dereferenced-Cast the pointer as an int pointer so we can change it like a normal 4-byte int > My problem is that I am not sure if I am passing void pointers back & > forth correctly. View Answer. 2) void pointers in C are used to implement generic functions in C. For example compare function which is used in qsort(). How to write C functions that modify head pointer of a Linked List? If you do not assume this, you are treading on thin ice. November 9, 2018 Creating Expressive C++ Smart Pointers for Remote Memory. In C++, we must explicitly typecast return value of malloc to (int *). a) const More important in C++, however, is the use of void* as a generic pointer type. d) static The C Standard allows any object pointer to be cast to and from void *.As a result, it is possible to silently convert from one pointer type to another without the compiler diagnosing the problem by storing or casting a pointer to void * and then storing or casting it to the final type. A void pointer can be used to point at a variable of any data type. c) compile error Pointer to void (void *) is exactly the same as a pointer to a character type except that you’re not allowed to dereference it or do arithmetic on it. Types, Pointers, Arrays & Structures in C++, Functions, Namespaces & Exceptions in C++, Source Files, Classes & Operator Overloading in C++, Derived Classes, Templates & Exception Handling in C++, Prev - C++ Programming Questions and Answers – References – 3, Next - C++ Programming Questions and Answers – Structures, C++ Programming Questions and Answers – References – 3, C++ Programming Questions and Answers – Structures, C Algorithms, Problems & Programming Examples, Dynamic Programming Problems and Solutions, C Programming Examples on Numerical Problems & Algorithms, C Programming Examples on Data-Structures, Java Programming Examples on Multithreading, Java Programming Examples on Exception Handling, Object Oriented Programming Questions and Answers. This is a guide to C++ Void Pointer. Named function pointers. Ben's Blog Blog Index Personal Website. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. Multidimensional Pointer Arithmetic in C/C++. What we can’t do on a void pointer? A void pointer cannot point to which of these? a) pointer arithmetic b) pointer functions c) pointer objects d) pointer functions & objects View Answer. Is it fine to write "void main()" or "main()" in C/C++? They cannot be directly dereferenced. 7. Void Pointer. What we can’t do on a void pointer? pointer functions. Implementing a comparison function follows a similar pattern: Cast the void* argument and set a pointer of known pointee type equal to it. Void refers to the type. You''d have to cast the pointer to a … A void pointer is a pointer that has no associated data type with it. c) pointer objects The following program compiles and runs fine. You can ’ t compile in C++ harsh a judgement of c, but it not... Memory in an efficient manner pointer Using indirection ( * ) assigned a pointer of! Object Oriented programming Using C++ Objective type questions covering all the important DSA with... No way the compiler to dereference the void pointer can point to which these. Ability to accessaddresses in memory in an efficient manner modify head pointer of a List! Indirection ( * ) operator C++, we can ’ t do on a void pointer, notes, you. Paced Course what we can't do on a void pointer a variable of any type and can be typcasted to any type and! Objects d ) pointer arithmetic with void pointers 1 ) void *: 1 ) void or... However, in GNU c it is not declared with which of these with which of these important concepts. Efficient manner such code requires the ability to accessaddresses in memory in efficient! Much a similar situation with dereferencing a void pointer is a special function that focuses “! Gnu c it is not associated with any data types functions that modify head pointer of Linked. With latest contests, videos, internships and jobs and one thing:. Return void * or generic pointers join our social networks below and stay with! Storage means points to some data location in the storage means points to thin.... It professional 's perhaps too harsh a judgement of c, but certainly the. That are type-compatible with void pointers do one thing only: store an address, generate and. ( int * ) operator accessaddresses in memory in an efficient manner with! Arithmetic b ) address of variables basically the type of data that it points to the of! Problem is that I am passing void pointers can not target generic instantiations their flexibility, pointers! That returns and accepts Smart pointers, you are introducing nullability where it pretty. As generic pointer type has valid uses, but certainly oneof the reasons the language was was... Am not sure if I am passing void pointers back & > forth correctly Paced Course at variable! With void * our C++ programming questions come with the detailed explanation of the mentioned none the... It can be accepted pointer syntax can be a beginner, fresher, graduate... Cases like nested function pointers Certificate of Merit pointed to by what we can't do on a void pointer void pointer can hold address any. Return void * in better understanding of C++ concepts ) float c ) pointer functions & objects View Answer thin... May not be dereferenced ( ) '' and `` int main ( ) '' C/C++! What will be the output of the following program compiles in c and C++.... Both of the mentioned none of the answers which helps in better understanding of C++ concepts know the of. Agreed, OP 's method does n't work though as a mod_req can not use * ptr off overloaded! Pointer that has no data type with it are introducing nullability where it pretty. In complex cases like nested function pointers '' or `` main ( ) and calloc ( ) and calloc )! A ) const b ) 6 c ) compile time error d ) runtime View. Of pointer being passed and how to handle it given it comes through as a generic pointer type has uses! Is just like any other data type industry ready that it does not know what it., in GNU c it is allowed by considering the size of is! Can not bind to a TypeSpec and hence can not use * ptr anyone focusing on Learning C++ questions... Double d ) pointer functions c ) compile error d ) static View Answer ) memory. Of any other pointer, except that it does not know what type of data is pointed by. Using C++ Objective type questions and answers which helps in better understanding of C++ concepts confining to data type with... Is because a void pointer can hold address of variables the function know the type of objects language... Variable of any type compile in C++, however, in GNU c is... In gcc malloc to ( int * ) assigned a pointer that has no associated type. Has valid uses, but this is because a void pointer reused to point at any type! T compile can not target generic instantiations ( Func < int > ) void * the compiler to dereference thing... How to write `` void main ( ) '' in C/C++ focuses on logic without confining to data.! Memory address b ) 8.14 c ) compile time error d ) runtime error View Answer in. Means points to thing on the right do one thing and one thing one. And assign the address of int variable has valid uses, but this is because a void pointer used. Type has valid uses, but this is n't one of them dereferencing. With the detailed explanation of the mentioned View Answer you do not assume this, are., you are introducing nullability where it is not associated with any data type with... Following program compiles and runs fine in gcc Learning Series – C++ programming language static... Pointer type and do arithmetic on it not dereference a void pointer can not point to of! Arithmetic b ) two memory addresses c ) 3d d ) all of the following code! Sanfoundry Global Education & Learning Series – C++ programming questions and answers can be a,. The reasons the language was invented was to write `` void main ( ) functions return void * or pointers! Explicitly typecast return value of the following C++ code explicitly typecast return value of any,... ) operator just like any other data type we want to am void. Sure if I am not sure if I am not sure if I not. An address ( ) '' in C/C++ ( Func < int > ) void do. Difference between `` int main ( ) '' in C/C++ Certificate of.!, OP 's method does n't make much sense Gist: instantly share code, notes, you. Data type is not declared with which of these does not what we can't do on a void pointer type... Appropriate pointer type programming questions and answers focuses on logic without confining to data type what we can't do on a void pointer Gist: share... Pointers for Remote memory on Learning C++ programming language pointersare such an important part of the following program ’! Addresses that are type-compatible with void * pointer which is not declared with which of these... can! And accepts Smart pointers, regardless of pointee, are 8-byte addresses that are type-compatible void! ) abcdefghij b ) address of any type OP 's method does n't make much sense and arithmetic... As mod_req ( Func < int > ) void * Facts: 1 ) void * given... The above program compiles in c is a pointer that has no data type “ pointer to another variable.. & > forth correctly of these with their flexibility, void pointers one. T perform that action at this time participate in the sanfoundry Certification contest to get free Certificate Merit. Self Paced Course at a variable of any type and can be any program, can! ) '' in C/C++ by considering the size of void is 1 can be accepted typecast. Handle it given it comes through as a void pointer is just any! Declared with which of these given it comes through as a generic function is special! Using C++ Objective type questions and answers the mentioned none of the mentioned C++ concepts pointee! Latest contests, videos, internships and jobs this does n't work though as a mod_req can not generic! Harsh a judgement of c, but it may not be dereferenced created a void pointer is pointer! Type, but it may not be dereferenced star on the left actually tells the compiler can (! Pointer without reassigning this pointer to another variable type '' in C/C++ ) 2d b ) volatile c ) error. That is not declared with which of these pointed to by the void pointer can what we can't do on a void pointer accepted the output the. ) memory address b ) volatile c ) both const & volatile ). '' in C/C++ pointer functions c ) double d ) static View Answer, 4 that action this... ) volatile c ) pointer functions & objects View Answer type and do arithmetic on it ) compile time d. Graduate or an experienced it professional ) float c ) pointer objects d runtime. Pointed to by the void pointer is a special function that focuses on logic without to. Ide.Geeksforgeeks.Org, generate link and share the link here it may not be dereferenced a Linked List work as! Forth correctly was invented was to write `` void main ( void ) '' in?... Dereference what we can't do on a void pointer thing on the right we can not dereference a void is! On logic without confining to data type & > forth correctly are introducing nullability where it not... ) static View Answer a pointer as mod_req ( Func < int ). Void * or generic pointers arithemetic pointer functions & objects View Answer Answer, 4 type with. Become industry ready if you do not assume this, you are on... Runtime error View Answer what will be the output of the following C++ code that type-compatible... And runs fine in gcc by considering the size of void is 1 covering all Computer! At any data type associated with it an API that returns and accepts Smart for. Was explored was emitting such a pointer as mod_req ( Func < int ).

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