C# :: Object Header Size?
Dec 25, 2014
In 32bit, the object header size is always 8bytes.
In 64bit, the object header size is always 16bytes.
Is this safe to assume or are there situations where the header size can be smaller/larger than the numbers above?(Haven't found anything on this, so I assume no?)
I need to know the exact size of the object header, because I need specifically pad a few classes I wrote to avoid false sharing along cache lines. Just need to make sure I have the sizes correct so I don't pad them wrong!
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Dec 1, 2014
Was missing the '.s'
I'm getting this error in the 'my_free' function here "bp->s.size += p->s.ptr->s.size;" and "p->s.size += bp->s.size;" here. This doesn't make sense to me because it seems to be the correct way to access the union, and In the "my_malloc" function I use a similar call "p->s.size = nunits;" and that works fine.
// gcc -o malloctest -Wall -g -ldl main.c
// ./malloctest
#include <stdbool.h>
[Code].....
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Mar 26, 2013
I need to use an instance of an object in a header file. The object requires a lot of pre-computation to be created.
I want to assign it to a "static const *NAMEobject*" field in the .h file, once it has been created. I assume that it is better to create it in another file and somehow pass it into the .h file.
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Apr 25, 2015
I'm working on a grocery store inventory project. One part is to have a shopping cart, where customers can put in up to 20 items. Because there can be up to 20 shopping carts at one time, I want to use a vector inside the cart object to represent all the individual food items.
Here's my code,
Header:
#ifndef CART_H
#define CART_H
#include <vector>
class Cart {
public:
Cart();
Cart(std::vector< int >, std::vector< int >)
[Code] ....
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Jul 19, 2014
Let's say I am using a library containing classes called class1 and class2 but both classes take three arguments to construct them. eg. class1(int a, int b, int c). and the same for class2
The below is an example of how to lay out the structure in the header and source file if class1 and class2 don't have any arguments in their constructor. But.... I'm not sure how to go about the below to take into account the constructor arguments of class1 and class2.
program.h
struct thestructure
{
thestructure(class1, class2); //constructor.
[Code].....
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Feb 5, 2014
hiclass Parent {
};
class Child : virtual public Parent {
};
What is the size of object of Class Child in following case?
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Feb 10, 2014
I am using Visual C++ to write an app. I write CMyObject class and may allocate a lot of instances of CMyObject object, so I want to reduce the size of CMyObject class.
What I can figure out to do is:
1. I can use the following code to get the accurate size used by a single instance of CMyObject object:
CMyObject Object;
//Get the size of memory allocated for CMyObject object
int nSize = sizeof(Object);
is that correct?
2.To reduce the size of CMyObject, I have several ideas:
(1)Change member function to static member function if it is possible, since each member function will take some spaces in the instance of CMyObject.
(2)Change virtual member function to member function if it is possible, since virtual member function may take more spaces.
(3)Eliminate unnecessary member variables to reduce spaces.
(4)Finally, if (1), (2) and (3) does not work well, then change CMyObject from class to a struct that only contains some member variables, thus will eliminate the spaces allocated for constructor and destructor of a class.
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Aug 20, 2013
What is the size of object in c++ , if there is no data member in the class ?
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Apr 11, 2013
My sample.h is
#include <string>
namespace xxx
{
class abc
[Code]....
My Question is when i compile this code in Linux platform Using g++ compiler My sample.o's Size is 1Kb.. But when the same code is compiled in Windows platform using VC++ Compiler , My sample.o's size is 42Kb..to reduce the size in windows... Is there any proble with '#include <string>' in Windows platform.
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May 16, 2014
I'm doing a compiler, and I'm using writing everything in headerfiles.
at the moment I have lexer.h, token.h and for this case I need reservedWords.h
reservedWords.h is made up of enums showing the needed words
in token.h I have a function called reservedWords reservedLookup(string str) which returns a reservedWord (enum)
now in lexer.h I have a function called Token* getNextToken() in which I need to make use of the function reservedLookup found in token.h
note that all of them are classes apart from reservedwords as in
class Lexer
{
public: .....
}
class token
{
public .....
}
how I can call that function?
I tried declaring reservedWords reservedLookup (string str) BUT obviously it's directing me as Lexer::reservedLookup and not as Token::reservedLookup
When I tried using Token::reservedLookup it gave me
E:Universitycompilerslexer.h|65|error: cannot declare member function 'Token::reservedLookup' within 'Lexer'|
N.B I use namespace std, that's why I didnot write std::string str
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Nov 27, 2012
Change the frame window size according to font size increases.
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Feb 1, 2013
I must take an old MFC project in VC++ 6.0 and make changes.
The problem is text size in screen is different from size in print preview.
for example with this font
Code:
CFont f50;
f50.CreateFont(100,0,0,0,FW_BOLD,0,0,0,DEFAULT_CHARSET,OUT_DEFAULT_PRECIS,
CLIP_DEFAULT_PRECIS,DEFAULT_QUALITY,FF_DONTCARE,"Frutiger LT Std 45 Light");
And this text
Code:
s=_T("Let's try to calculate the size of this text");
and with MM_LOMETRIC map mode
GetTextExtent() returns me:
On screen: (1595,99)
Ink printer + print preview: (1589,100)
PDFCreator + print preview: (1580,100)
comparing with screen size the height is bigger but lenght is smaller. I don't understand.
I can understand that different printers process the fonts in different way and then to have different lenghts. That's not the problem. The problem is I need to simulate in screen the same behaviour i will have on printer because these texts are being aligned in the document, and I don't want to see that the text si aligned different in text than in paper.
What can I do to render the text on screen with the same size I will have on the printer? Print preview is doing it. Should I change the font parameters? is something related with pixels per inch?
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Sep 16, 2013
When including a header file in stdafx.h, should that file still be included in the source file where it is actually used?
If it is included in both places, is the one in the source file ignored?
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Jul 11, 2013
I was wondering why, in C, the sizeof of a struct is larger than the the sum of all the sizeofs of it's members. It only seems to be by a few bytes, but as a bit of a perfectionist I fine this a bit annoying.
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Mar 16, 2013
will copy constructor does object initialization using another already created object? I understand that it can be applied for object initialization and not for assignment.Is it correct?
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Jul 3, 2014
I have a method to take a Tile object and make an instances of it based on some data from the original object. Than it is suppose to manipulate the a specific instance and save the results. The first loop through it works but it changes all instance as well as the base.
public static int recurse(int count, Tile[,] b,Huristic h,int check) {
if (check==1) {
boardState.Add(B)/>;
return check;
} if (check == 0)
[Code] .....
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Dec 13, 2012
#include "B.h"
class A {
public :
A()
{
s_b = new B();
b = new B();
[Code] ....
In my project i have seen static object as above . But not able to know what is the exact use of it and how they are different from general object .
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Sep 11, 2014
a function returns a temporary object like
int myfun(){
int x = 0;
return x;
}
this function will return a temporary integer now void fun1(const int & num); this function can receive from myfun().BUT void fun2(int & num); this function cannot receive from myfun() Why is that, Moreover what is lifetime of a temporary object like one returned in myfun() ???
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Mar 28, 2014
I am trying to use web api in order to return custom json response keys. For this i have return a custom class to return json response
Custom Class:
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
[Code].....
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May 4, 2013
I have a combobox with Items 1024
2048
4096
8192
String cach = form.comboCache.SelectedItem.ToString();
I am using the above code to retrive an item selected by user,But this line is giving an exception "Null Reference Exception, Object reference not set to an instance of an object"
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Mar 28, 2014
I am using session to pass object from controller to custom class in MVC Web API. here is my code, i am getting error at session.
public HttpResponseMessage Get()
{
var person = db.Persons.ToList();
[Code]....
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Aug 23, 2013
In Visual Studio 2010 C++
I have a series of existing text objects
The text properties names are
item1_lbl,
item2_lbl,
item3_lbl,
….
Based on a selection I want to change an object. I generate the name of the object I want to change in a string so from this string is there a way to get a pointer to the correct text object that is same name?
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Sep 22, 2014
I'm trying to figure out how I can create a vertex array object at offset of a vertex buffer object.I've created the buffer object. I'd like the "texs" idnex data to start at the texture coordinate content of the vertex_t structure.
Type definitions:
struct vertex_t {
vector3d_t position;
float s; // Texture coordinate s
float t; // Texture coordinate t
};
Code so far:
// How do I make this start at a certain spot of the VBO?!
glVertexAttribPointer(texs, 2, GL_FLOAT, GL_FALSE, sizeof(vector3d_t), nullptr;
//...
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Sep 28, 2013
i have 1 class:
from here: [URL]
template <typename Container, typename ValueType, void (Container::*setptr)(ValueType t),ValueType (Container::*getptr)(), int nPropType=3>
class property {
[code]....
(but i did the version 2;))
my question is: can i put these:
void setContainer(Container* cObject) {
m_cObject = cObject;
}
in header template?
i did these:
template <typename Container,Container* cObject, typename ValueType, void (Container::*setptr)(ValueType t),ValueType (Container::*getptr)(), int nPropType=3>
class property {
[Code] .....
how use it:
property <person2,this,string,&person2::setname,&person2::getname> Name;
(person2 is the class name)
errors messages:
"C:UsersJoaquimDocumentsCodeBlocks esteventsmain.cpp|31|error: invalid use of 'this' at top level|"
"C:UsersJoaquimDocumentsCodeBlocks esteventsmain.cpp|31|error: template argument 2 is invalid|"
how can i use the 'this' in template header?
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Mar 23, 2013
1. Write a program the calculates the volume of a sphere.
Use a define to set Pi to 3.14 and a macro for the formula for the sphere.
V = 4/3PiR3.
In main ask for the radius (R).
Pass it to a function where you calculate the volume and return it to main and print the volume in main.
Use float values. (Save this program as you'll need it later.)
Code:
#include<stdio.h>
void fun (float);
main()
[Code].....
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Nov 2, 2013
I have a piece of code in C with header files included. I run it on Mac OS X Maverick with XCode 4.6.2 installed. GCC is also installed. Note that Command Line Tools in XCode are already installed.
When I compile it, the error I receive says something like this:
add.c:1:19: error: stdio.h: No such file or directory add.c:2:20: error: stdlib.h: No such file or directory add.c:3:20: error: unistd.h: No such file or directory
However when I run it on Ubuntu, it compiles without a problem.What to do?
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