Why is the size of an empty class 1? Why is the class still one when I add a char member to the class?//using turbo c++ 3.0, yes I know I'm using a very old c++ compiler and software
View 3 RepliesWhat is the size of object in c++ , if there is no data member in the class ?
View 3 Replies View RelatedWas 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].....
Code:
cout<<"Enter Filename for input e.g(inp1.txt .... inp10.txt):"<<flush;
cin>>filename;
ifstream inpfile;
inpfile.open(filename,ios::in);
if(inpfile.is_open())
[Code] .....
The compiler creates virtual table for the base class and also for the derived class whether we override it or not.
That means each class has separate virtual table. when we get the size of the each class with out any data members... the size of base is -- 4 bytes(64 bit) and the size of derived is -- 1
The size of base class 4 is correct since it creates the virtual pointer internally and its size is member data + virtual pointer, but it in this case I have included any data members so it has given 4 byts.
But why in case of derived is 1 byte, since it the derived class has overridden the virtual function from base, this will also contains the virtual pointer which will be pointing to derived class Vtable, it the size of the class suppose to be 4 instead of 1 byte.
#include<iostream>
class A{
public:
[Code].....
How to initialize a static member of a class with template, which type is related to a nested class?
This code works (without nested class):
#include<iostream>
using namespace std;
struct B{
B(){cout<<"here"<<endl;}
};
template<typename Z>
[Code] ,....
I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
I have function that looks like this myfoo(char* Name) Now i want to compare this name to another one . But the another name is a pointer . This my code :
bool Tribe::RemoveSurvavior(char *H_Name) {
const char *p;
p=SurpointArr[i]->GetSurvivor_Name();
}
I need to compare if p is same as H_Name.
Mine is do it with for on each element but when i use sizeof it gives me size of char and not real size of the name.
So I have an ImageManager class, Board class, and Box class. In Board.h I can declare ImageManager imgr; and in Board's constructor I can use imgr and its functions and such. However, in Box.h when I try and declare ImageManager imgr; I get the error "cannot access member declared in class ImageManager". Both declarations are under private, and exactly the same, but one doesn't work. Also, is there a way to only have one instance of ImageManager?
View 19 Replies View RelatedSo I'm trying to make a program, Which has nothing to do with the topic. But I ran into a problem.
I need to get a char array size of 6 doing:
char myChar[6];
but the size (6) is undefined until user input.
So I need to do char myChar[var]; (Var being 6 for now).
When I do:
char myChar[6];
It works!!!
But when I do:
int val = 6;
char myChar[val];
It doesn't work.
I want to save the char[8][8] // fixed size 2 dimension array
to a vector
such as
vector<?????> temp;
is there anyway to approach this?
I have a class that defines a window (a popup dialog of sorts), and I want the name of that window to be constant. The only problem is that the name of the popup needs to match the title of the parent window, and I get the name of the parent in the constructor. So how do I go about defining this member variable to be constant and initializing it with a value in the constructor?
I want to do something like this, but I know this isn't allowed:
/* class.h */
class foo {
public:
foo(*parentWindowPtr);
[Code] .....
I should mention that yes the name of the parent window is const char *, and I would like to keep it this way.
I've been in a strange problem. Im in need to have a dynamic character size, but that increases the outputsize of my program by almost 50kb. (while the program was 11kb previously).
Example:
Char One[7000]; (11kb output)
int Z = 7000;
Char Two[Z];
I'm working on a piece of code written long time ago. Without getting in the details or too much context here, there is a function that declares an array of char of a size of 350,000 elements, in order to fill it (using a pointer) with the list of all running processes on the machine (using "ps -ejf" on a Linux box).
The size of the char array has been changed from 40,000 to 350,000 sometime along the years, probably because of a lack of space required.
What kind on data structure / storage would you use to store the running processes in order to eventually search for a value in it?
I am having compiling issues and am looking for an explanation as to what is causing the error and how to fix it. The declaration of 'g4vuplInstanceID' seems to be global in scope in my option, however I may be wrong.
Compiler Error: error: 'class myPhysListGeneral' has no member named 'g4vupInstanceID'
#include "G4VUserPhysicsList.hh"
#include "G4VUPLSplitter.hh"
#include "G4VPhysicsConstructor.hh"
#include "myPhysListGeneral.hh"
#include "G4ParticleDefinition.hh"
#include "G4ProcessManager.hh"
#include "G4ParticleTable.hh"
[code]....
How can a member function in my derived class call the same function from its base class?
View 1 Replies View RelatedI mount a function (parameter - numeric vector; returns a string). However, this same function is used in several classes. To avoid that I keep duplicating the same code within these classes there is a way to do that as the code below?
std::string func( const vector<int> vec ) {
//processamento
return result;
} class A {
[Code] ....
whether i can define a member function inside a class or not in C++. Is the following code is legal?
#include<iostream> using namespace std;
class adder {
private:
int a;
int b;
int c;
int answer;
public:
[code]....
I am looking to have a member of type bitset in a C++ class. Is it possible ?
Something like below:
Class abc
{
bitset<32> var;
}
This code:
#include <iostream>
class Foo {
};
int main() {
Foo foo;
std::cout << sizeof ( foo ) << std::endl;
std::cin.get();
return ( 0 );
}
produces this result: 1
Why is the size of an instance of Foo 1, although it doesn't have any member variables?
If you are doing some big program, usually, how do you organize the files? Put the class and its member in head file, but where to declare non member functions and where to define them? I don't want to put them all in one cpp file. If not, how to make them visible to the main cpp file?
View 4 Replies View Relatedwe have to make a Invoice class which has a function called computeInvoiceAmount() which multiplies the price and the quantitiy which are private member of the class.
double computeInvoiceAmount(){
return quantity * pricePerItem;
}
This is my function, but if i compile it i get the following error:
"Invoice.cpp:53:11: error: "quantity" was not declared in this scope" and "Invoice.cpp:53:22: error: "pricePerItem" was not declared in this scope"
I tried it with the get functions but i get the same error.
Full code is here: [URL]
I did know that the size of a class is increased by 4 bytes (32bit compiler) if the class has a virtual function. I wrote one program and it is giving strange output. I am using linux g++ compiler.
The program and output is as below
Code:
#include<iostream>
using namespace std;
class Base {
public:
void fun() {
[Code] ....
output=4
Code:
#include<iostream>
using namespace std;
class Base {
public:
virtual void fun() {
[Code] .....
Output is 16
I have the following scenario :
Code:
class test {
public :
int num;
};
int main() {
test t1;
test *ptr = &t1;
int test :: *mem_ptr = &test::num;
}
I need to access mem_ptr (pointer to a class member) through :
a. object (t1)
b. pointer to the object (ptr).
How can i do that ?
I want to have a template function that is a member of a class. Is this possible? This code snippet is how I would think the syntax would go, although it doesn't compile. How would I achieve the same effect?
Code:
class myclass {
public:
int member ;
} ;
template <typename T> void myclass::func( T& arg )
[Code] .....
hiclass Parent {
};
class Child : virtual public Parent {
};
What is the size of object of Class Child in following case?