Describe the “placement new" and why would i use it?, C/C++ Programming

Assignment Help:

Describe the “placement new" and why would I use it?

How do i develop a subscript operator for a matrix class?, Employ operator ...

Employ operator () instead of operator[]. While you have multiple subscripts, the cleanest way to do it is along with operator () instead of with operator[]. The reason is that

C program for reverse the word in string, C Program for REVERSE THE WORD IN...

C Program for REVERSE THE WORD IN STRING #include conio.h> #include stdio.h> #include string.h> void main() {           char a[50],b[25][25],temp;           i

Padovan String Problem Description A Padovan string P(n) for a natural number n is defined as: P(0) = ‘X’ P(1) = ‘Y’ P(2) = ‘Z’ P(n) = P(n-2) + P(n-3), n>2 where + denotes s

Input function

Program, Define a class polynomial with three private data members a, b and...

Define a class polynomial with three private data members a, b and c of type double to represent the coefficient of two degree polynomial(ax^2+bx+c). Include a constructor in a pol

Find area under curve, write a c program to find the area under the curve4...

write a c program to find the area under the curve4 f=(x) between x=a and x=l integrate y=(x) between the limits of a and b Solution: #include float    start_point,

Identifier and constant, What are  Id e n t i f ie rs a n d C o...

What are  Id e n t i f ie rs a n d C o n s t a n ts in C++? Id e n t i f ie r a n d C o n s t a n t : I d e n t i f ie r

HASH., Define hash functions. Explain the Division method, Mid square metho...

Define hash functions. Explain the Division method, Mid square method and Folding method of hash functions.

#compiler design limit the instruction, #compiler design limit the instruct...

#compiler design limit the instruction#

C program to remove vowels in sentence , C program to remove vowels in sent...

C program to remove vowels in sentence : void main() {                 char  str[100];                 int n;                 printf("enter string\n");

 3/15/2013 5:37:27 AM A: There are several uses of placement new. The simplest use is to place an object at a specific location in memory. It is done by supplying the place as a pointer parameter to the new part of a new expression: #include // Must #include this to use "placement new" #include "Fred.h" // Declaration of class Fred void someCode() { char memory[sizeof(Fred)]; // Line #1 void* place = memory; // Line #2 Fred* f = new(place) Fred(); // Line #3 (see "DANGER" below) // The pointers f & place will be equal ... } Line #1 creates an array of sizeof(Fred) bytes of memory, that is adequate to hold a Fred object. Line #2 creates a pointer place which points to the first byte of this memory (experienced C programmers will note  down that this step was needless; it''s there just to make the code more obvious). Line #3 in essence just calls the constructor Fred::Fred(). The this pointer in the Fred constructor will be equal to place. Therefore the returned pointer f will be equal to place. ADVICE: Don''t use this "placement new" syntax if not you have to. Use it only while you really care that an object is placed at a specific location in memory. For instance, while your hardware has a memory-mapped I/O timer device, and you wished to place a Clock object at that memory location. DANGER: You are taking solitary job that the pointer you pass to the "placement new" operator points to a region of memory which is sufficient and is appropriately aligned for the object type which you''re creating. Neither the compiler nor run-time system makes any effort to check whether you did this right. If your Fred class requires to be aligned on a 4 byte boundary however you supplied a location which isn''t properly aligned, you can have serious disaster on your hands You have been warned. You are also exclusively responsible for destructing the placed object. It is done by explicitly calling the destructor: void someCode() { char memory[sizeof(Fred)]; void* p = memory; Fred* f = new(p) Fred(); ... f->~Fred(); // Explicitly call the destructor for the placed object } It is about the only time you ever explicitly call a destructor. Note: there is a much apparent but more sophisticated way of handling the destruction / deletion situation.