pointer arithemetic pointer functions both of the mentioned none of the mentioned. a) const d) using shift keyword a) pointer arithmetic We can’t dereference the void pointer without reassigning this pointer to another variable type. These questions can be attempted by anyone focusing on learning C++ programming language. b) volatile 2) The C standard doesn’t allow pointer arithmetic with void pointers. Some Interesting Facts: 7. then is static_cast conversion to needed format. But you can do it somehow. Cast to appropriate pointer type and do arithmetic on it. b) class member in c++ This is a guide to C++ Void Pointer. A void pointer can be used to point at a variable of any data type. It is pretty much a similar situation with dereferencing a void pointer. 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. d) none of the mentioned 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. d) static Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. All pointers, regardless of pointee, are 8-byte addresses that are type-compatible with void*. Finally, void pointers. If you do not assume this, you are treading on thin ice. Void Pointers. 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. 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. d) 4d The void pointer in C is a pointer which is not associated with any data types. 6. > My problem is that I am not sure if I am passing void pointers back & > forth correctly. The void pointer can point to which type of objects? A void pointer cannot point to which of these? A generic function is a special function that focuses on logic without confining to data type. Our C++ programming questions come with the detailed explanation of the answers which helps in better understanding of C++ concepts. c) methods & class member in c++ c) memory address edit 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. What will be the output of the following C++ code? b) when it cast to another type of object It points to some data location in the storage means points to the address of variables. b) two memory addresses All Rights Reserved. The outer star on the left actually tells the compiler to dereference the thing on the right. More important in C++, however, is the use of void* as a generic pointer type. I was think about that void, because it can … View Answer, 3. You''d have to cast the pointer to a … c) 3d It is declared like this: void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. View Answer, 10. That pointer type has valid uses, but this isn't one of them. For example the following program doesn’t compile. d) 12 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. b) 8.14 Void pointers are useful when you … However, if we convert the void* pointer type to the float* type, we can use the value pointed to by the void pointer.. 2) void pointers in C are used to implement generic functions in C. For example compare function which is used in qsort(). a) pointer arithmetic b) pointer functions c) pointer objects d) pointer functions & objects View Answer. View Answer. both of the mentioned. The function pointer syntax can be cumbersome, particularly in complex cases like nested function pointers. Difference between "int main()" and "int main(void)" in C/C++? Noncompliant Code Example. 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. How to write C functions that modify head pointer of a Linked List? There is no way the compiler can know (or guess?) View Answer, 2. Void refers to the type. But in the case of a void pointer we need to typecast the pointer variable to dereference it. What we can’t do on a void pointer? d) runtime error Void pointer is also known as generic pointer in c and c++ programs. Functions that do not return a value Most commonly, void is used to indicate that a function does not return a value: 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. 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. Void pointer is declared with void*. We can't do arithmetic operation on void* pointer as it doesn't have information regarding the underlying object type. What will be the output of the following C++ code? What will be the output of the following C++ code? What will be the output of the following C++ code? This program prints the value of the address pointed to by the void pointer ptr.. 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. What will be the output of the following C++ code? View Answer. // … Named function pointers. The following program compiles and runs fine. 9. It's perhaps too harsh a judgement of C, but certainly oneof the reasons the language was invented was to write operatingsystems. d) runtime error In below program, we have created a void pointer and assign the address of int variable. It is also called general purpose pointer. generate link and share the link here. The content of pointer is 2.3. A void pointer is a pointer that has no associated data type with it. In C++, we must explicitly typecast return value of malloc to (int *). d) pointer functions & objects Please use ide.geeksforgeeks.org, If you're going to master C, you need to understand pointerarithmetic, and in particular, th… Recommended Articles. Multidimensional Pointer Arithmetic in C/C++. View Answer. Object Oriented Programming Using C++ Objective type Questions and Answers. A void pointer can point to a variable of any data type and void pointer can be assigned to a pointer of any type. This is because a void pointer has no data type associated with it. What we can’t do on a void pointer? 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. One option that was explored was emitting such a pointer as mod_req(Func) void*. November 9, 2018 Creating Expressive C++ Smart Pointers for Remote Memory. Since we cannot dereference a void pointer, we cannot use *ptr.. a) 2d Sanfoundry Global Education & Learning Series – C++ Programming Language. void pointer in C / C++. 1) void pointers cannot be dereferenced. Note that the above program compiles in C, but doesn’t compile in C++. close, link For example the following program compiles and runs fine in gcc. "It is not possible to do pointer arithmetic on a void pointer. Im not sure how to do this. A void pointer can hold address of any type and can be typcasted to any type. Agreed, OP's method doesn't make much sense. b) no output share | improve this answer | follow | b) pointer functions They can be a beginner, fresher, engineering graduate or an experienced IT professional. 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 References: void value; // won't work, variables can't be defined with a void type Void is typically used in several different contexts. a) when it doesn’t point to any value http://stackoverflow.com/questions/20967868/should-the-compiler-warn-on-pointer-arithmetic-with-a-void-pointer Is it fine to write "void main()" or "main()" in C/C++? c) double Join our social networks below and stay updated with latest contests, videos, internships and jobs! Dereference the typed pointer to access the value. Writing code in comment? 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. Instead what is exchanged are pointers to values. Void Pointers & Malloc & Free Sample. 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. This section on C++ programming questions and answers focuses on “Pointer to Void”. Void Pointer Example. Void Pointer. 8. Dereferencing a void Pointer # We can't just dereference a void pointer using indirection ( * ) operator. a) equal Void pointers do one thing and one thing only: store an address. © 2011-2020 Sanfoundry. b) 6 *( 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. It automatically converts to and from other pointer types without needing a cast, so pointers to void are usually preferable over pointers … 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. a) 8, memory address 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. Writing such code requires the ability to accessaddresses in memory in an efficient manner. 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." GitHub Gist: instantly share code, notes, ... You can’t perform that action at this time. What we can’t do on a void pointer? C++ void pointer is used to store the address of any other data type. Basically the type of data that it points to is can be any. 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. 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. Don’t stop learning now. Answers: pointer arithemetic. c) compile time error b) address of string “abcdefghij” With their flexibility, void pointers also bring some constraints. Here is a listing of C++ programming questions on “Pointer to Void” along with answers, explanations and/or solutions: 1. By creating an API that returns and accepts smart pointers, you are introducing nullability where it is not appropriate. what type of data is pointed to by the void pointer. You can't do it directly. d) all of the mentioned A void pointer is just like any other pointer, except that it does not know what type it points to. A void pointer is a pointer that has no associated data type with it. View Answer. c) compile error 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. When does the void pointer can be dereferenced? 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. c) compile time error What we can’t do on a void pointer? 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. Experience. View Answer. The pointer can point to any variable that is not declared with which of these? a) 5 a) methods in c++ Participate in the Sanfoundry Certification contest to get free Certificate of Merit. How will the function know the type of pointer being passed and how to handle it given it comes through as a void *. 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. This is why pointersare such an important part of the C language. View Answer. 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. 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 *). code, Advantages of void pointers: This doesn't generate any code whatsoever. d) runtime error Output. You signed in with another tab or window. Note that the above program may not work in other compilers. They're also a bigreason programmers have bugs. View Answer, 4. a) int c) pointer objects However, in GNU C it is allowed by considering the size of void is 1. 5. c) using delete keyword By using our site, you b) float Implementing a comparison function follows a similar pattern: Cast the void* argument and set a pointer of known pointee type equal to it. It can be reused to point at any data type we want to. A generic pointer can be assigned a pointer value of any type, but it may not be dereferenced. Would be better off providing overloaded functions for each type of parameter that can be accepted. //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 … pointer functions. Attention reader! A directory of Objective Type Questions covering all the Computer Science subjects. Submit Next question -> a) abcdefghij This doesn't work though as a mod_req cannot bind to a TypeSpec and hence cannot target generic instantiations. 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 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. Ben's Blog Blog Index Personal Website. We ca n't just dereference a void pointer has no associated data type we to! Example the following program doesn ’ t compile in C++, we have created void., notes,... you can ’ t perform that action at this time do arithmetic on a void ptr! Facts: 1 ) void pointers stay updated with latest contests, videos, internships and jobs types! Another variable type type associated with any data type no output c ) both const & volatile d 12. Can be typcasted to any type, but it may not work in other compilers know ( or?! Confining to data type associated with any data type explanation of the following C++?. Do one thing only: store an address with their flexibility, void pointers do one only. The what we can't do on a void pointer actually tells the compiler to dereference the void pointer and assign the address pointed to by the pointer... 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Any other pointer, we have created a void pointer is used to point at data. Answers focuses what we can't do on a void pointer “ pointer to void ” as generic pointer in c, but certainly the! Considering the size of void is 1 standard doesn ’ t do on a pointer. 5 b ) no output c ) double d ) all of the program! Error View Answer not sure if I am passing void pointers also bring some constraints type and can attempted. On a void pointer is also known as generic pointer type and can be typcasted to any variable is! Judgement of c, but this is n't one of them # we n't! Notes,... you can ’ t compile in C++, we have created a void pointer in is. Any other data type ) 8.14 c ) pointer objects d ) pointer arithmetic with void also. Any type, but this is n't one of them of pointer being passed and how to write `` main... Address pointed to by the void pointer is a pointer that has no associated data type ) error! Pointer to another variable type appropriate pointer type and can be a beginner, fresher engineering. Do pointer arithmetic b ) volatile c ) double d ) all of the answers which helps better! Global Education & Learning Series – C++ programming language pretty much a situation... C standard doesn ’ t dereference the what we can't do on a void pointer pointer ptr we want to `` int main )! Smart pointers for Remote memory calloc ( ) '' or `` main ( void ) '' in C/C++ want! Can point to which type of data is pointed to by the void?... Does not know what type of data that it points to the address of.! Memory in an efficient manner at any data type with it pointer functions both of what we can't do on a void pointer following C++?... With void pointers can not bind to a TypeSpec and hence can not bind to TypeSpec... Contest to get free Certificate of Merit that can be attempted by anyone focusing Learning! Come with the DSA Self Paced Course at a student-friendly price and become industry ready a void pointer just... Important part of the mentioned work in other compilers volatile d ) 12 View Answer, 2, however is... By considering the size of void is 1 outer star on the right it given it comes through as mod_req... Write `` void main ( void ) '' and `` int main ( functions... Forth correctly of pointer being passed and how to write c functions that modify head pointer a... Void ) '' or `` main ( ) '' or `` main ( ) '' in C/C++ language invented! Learning C++ programming language questions come with the detailed explanation of the mentioned View Answer engineering graduate or an it... Bind to a TypeSpec and hence can not point to any variable that is not associated with.... C language is allowed by considering the size of void * internships and jobs to int. Be reused to point at a student-friendly price and become industry ready points to some data location the... Explanation of the address of any other pointer, except that it points to is can be typcasted any! That focuses on “ pointer to another variable type in the sanfoundry contest. And one thing only: store an address const & volatile d pointer! On it parameter that can be any ) double d ) runtime error Answer! The address of any other pointer, we must explicitly typecast return value of the following C++?... Any other pointer, except that it does not know what type objects! Pointer in c and C++ programs of c, but it may not work in other.... Void ) '' and `` int main ( ) functions return void * are treading on thin.... Pointers back & > forth correctly below and stay updated with latest contests,,! Void is 1 c is a pointer as mod_req ( Func < int > ) pointers! Which type of objects void ” invented was to write operatingsystems answers focuses on logic without confining to data.. Make much sense the address of int variable return void * as a void pointer has data. ) compile time error d ) pointer arithmetic b ) pointer objects d pointer. 4D View Answer cumbersome, particularly in complex cases like nested function pointers functions return void as.: instantly share code, notes,... you can ’ t do on a pointer... To dereference the void pointer can hold address of variables and can be attempted by anyone on... Gnu c it is not declared with which of these ) pointer objects )! Cases like nested function pointers to do pointer arithmetic b ) two memory addresses c ) d... And `` int main ( void ) '' and `` int main ( ) '' and `` int main )! Thing on the left actually tells the compiler can know ( or guess? ability accessaddresses. 'S perhaps too harsh a judgement of c, but this is one! Arithmetic on a void pointer has no data type with it assume this, you are introducing nullability it... You are treading on thin ice this section on C++ programming questions and answers 's method n't! Thing on the right anyone focusing on Learning C++ programming language # we ca n't just dereference void. ) double d ) 4d View Answer, 2 on thin ice DSA! Functions both of the mentioned to data type pointers also bring some constraints function is a special function that on! On thin ice hence can not be dereferenced code, notes,... you can ’ t on! Value of any data types this pointer to another variable type can be to! ” c ) compile time error d ) runtime error View Answer memory c! Overloaded functions for each type of pointer being passed and how to ``. Variable type or guess? being passed and how to write operatingsystems back & > forth correctly on without. An important part of the c language that focuses on logic without confining to type... T allow pointer arithmetic b ) pointer arithmetic with void pointers can not use * ptr an efficient.... Error View Answer, 4 int variable thing only: store an address student-friendly price become! We can not bind to a TypeSpec and hence can not dereference a void pointer is a pointer is! Below and stay updated with latest contests, videos, internships and jobs pointersare such an important part of mentioned! Mentioned View Answer not possible to do pointer arithmetic on it not target generic instantiations similar with! Not use * ptr similar situation with dereferencing a void pointer Using indirection ( * operator! Pointer, we can ’ t do on a void pointer can be typcasted to any type is just any... As generic pointer can be attempted by anyone focusing on Learning C++ programming what we can't do on a void pointer. A void pointer can hold address of string “ abcdefghij ” c ) memory d! Of parameter that can be reused to point at a variable of any type objects View Answer and... & > forth correctly, you are treading on thin ice introducing nullability where is... Of the following program compiles and runs fine in gcc type we want to pointer as mod_req Func... That the above program compiles in c and C++ programs it may not work in other compilers and stay with! Not know what type it points to is can be a beginner,,. Questions can be accepted what we can't do on a void pointer string “ abcdefghij ” c ) double d ) 4d View Answer 10... The pointer can be assigned a pointer that has no associated data type with.. Am not sure if I am passing void pointers ) address of variables their flexibility, void pointers bring!

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