C++ :: How To Know If Variable Has Been Accessed
Jul 21, 2014
How to tell whether a variable has been accessed in memory, no matter what it's been used for... Whether it's actually been set to something else, or whether it's been get for an operation or function call that doesn't actually do anything to affect the variable itself. Either way the variable has been "accessed" for something.
I'm not entirely certain that it's possible to detect a program getting the variable but I know that programs exist where they can trace what has accessed a certain part of memory... CheatEngine is one example, although I'm not entirely sure whether this can only detect changes in the variable and then trace what did it
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May 17, 2013
Suppose I have a class "A", which has a method "void AMP_call()" that calls paralel_for_each in which another method, "float amp_function(float) restrict(amp)". When I call that method, can it then use members of "A"?
class A {
void AMP_call();
float amp_function(float) restrict(amp); // do something on a device
float allowed_variable;
std::vector<bool> not_allowed;
[Code] ....
Another way to frame my question, perhaps to make it easier to understand what I am after, would be that I want to know what happens if an amp-restricted method is called where the body of the class itself (which is not amp-compatible and afaik doesn't have to be since it's not passed to the device) may contain members that are not amp-compatible.
All of the msdn blogs I could find deal with which functions and methods can be called from within a parallel_for_each loop, but not with which variables are available to the lambda function itself.
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Sep 9, 2013
I'm redesigning some code and I'm wondering what the best ways to store and access certain data is. The characteristics are as followed:
1) Based on data from a file, a distance matrix (N x N) is calculated.
2) Once the matrix is complete, the data will never change (unless a new file is read, but I can work around that by iteratively calling the problem with a new datafile on as command line parameter).
3) The data from the matrix is accessed billions of times from pretty much every other line of code.
In my old version, I had a class "Data" which a sub-class "Data::Distance" and I would put a reference in every other class that needed it. Now, my class hierarchy will be much flatter (basically all logic will be in one class; other classes will be POD structs).
Given the characteristics of the Distance table, is there a way to store them in a very efficiently-accessible way? Does it matter if it's stored in the main class where all the action happens in contrast to being a different class? Does making it static improve the performance? Casting it to const? Anything?
Again, the data is accessed billions of times so even minor differences can save a lot of time.
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Apr 24, 2014
Here in below code, the private data member is accessed directly using dot operator IN COPY CONSTRUCTOR and the program runs without error.
#include <cstdlib>
#include <iostream>
using namespace std;
class array {
int *p;
int size;
public:
array(int sz)
[code]....
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Feb 25, 2014
I'm getting some errors while i try to make a program code in C#Net. Here is the part of code that are returning error and a printscreen...
public static void Func_Register(string function, Del func) {
funcs.Add(function, func);
return;
}
Image 1: [URL] ....
private void console_Load(object sender, EventArgs e) {
CAPI.SetRTB(cmd_text);
CAPI.Func_Register("Console.Test", test);
CAPI.Func_Register("APP.Exit", Application.Exit);
[Code] .....
Image 2: [URL] ....
The idea of the code is to make a console to parse some commands. And have some commands with arguments and others no. Without the static the program return other error that is...
Image 3: [URL] ....
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Mar 15, 2013
I currently have globally declared arrays, which are accessed by multiple functions. I want to turn the program so that the arrays are no longer globally declared, but are passed to functions by reference.
I have one problem with passing the arrays: I found that, through debugging, I HAVE TO resize the array when I pass it by reference. For instance, I was using int a[10] when it was globally declared, when it is passed by reference with size 10, it does not work, instead it should be higher than 10 (certain number). Why is this happening? I do not get it...
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May 18, 2013
"A nested class has free access to all the static members of the enclosing class. All the instance members can be accessed through an object of the enclosing class type, or a pointer or reference to an object."
How can the members be accessed through an object of the enclosing class type? I understand the pointer and reference part because for them you dont need the full definition, but for creating a object you do?
Also it has free access to all static members because the nested class is part of the enclosed class and with static it exists in everything inside the enclosing class? Right or am I missing something?
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Oct 17, 2012
I have a basic vector/point class where I've overloaded a bunch of arithmetical operators:
Code:
#pragma once
class point {
public:
point() {
}
point(float p_x, float p_y, float p_z) : x(p_x), y(p_y), z(p_z)
[Code] ...
I can use it fine like
Code:
point p(50,50,50);
point q(50,50,50);
point t = p * q + q;
However when I put this point type into a struct and try to access the members after passing it through by const reference:
Code:
struct sextic {
point a,b,c,d,e,f,g;
};
inline static sextic sexticDifference(const sextic &p_sextic1, c
[Code] ....
This gives me an "operator not defined" error for compilation.
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May 10, 2013
I would like to convert a float or double variable into unsigned char variable and back.
float number_float = 23.453f;
unsigned char* number_char = (unsigned char*)malloc(sizeof(float));
number_char = reinterpret_cast<unsigned char*> (&number_float);
float* number_float_0 = reinterpret_cast<float*>(&number_char);
I am not getting the same value back.. why?
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May 1, 2013
I am having trouble compiling my interface. I am trying to store a reference variable as a member variable of the interface object. Compiler says that the variable has not be initiated correctly.
LCD inherits from VisualInterface which is expecting a DisplayDriver object to be passed in (DisplayDriver is another interface, but thats not important).
I pass the displayDriver object in when LCD is instantiated in maininterfaces.zip
I was pasing it before as a pointer but was told that this could cause me problems with memory leaks and a reference was better, but now I cant seem to get it to compile.
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Mar 2, 2013
This problem is best explained by looking at its output below. I stored 15 different values but when retrieved some are wrong.
#include <iostream>
using namespace std;
class A {
public:
int ** pointer;
[Code] ....
I need to store and retrieve the 15 different values correctly. How to solve this? The main thing is, I need to store the pointer in class A objects.
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Sep 8, 2013
I have to write a loop assigning a variable x to all positions of a string variable and I'm stuck. I don't have extensive experience with arrays and I'm also a bit confused about C-String. The problem is below.
"Given the following declaration and initialization of the string variable, write a loop to assign 'X' to all positions of this string variable, keeping the length the same.
char our_string[15] = "Hi there!";
(Please note this is a 'C-string', not C++ standard string.)"
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Oct 25, 2014
I need to transform a local variable into a global variable so I can use it in one of my functions. I thought about passing the value as a parameter to this function but I can do this since the function is called inside the while loop and this variable counts how many times the while loop does (so the final value is outside the loop). Example to visualize better:
Code:
while(condition) {
function(parameter1, parameter2);
count = count + 1;
}
printf("%d
", count);
So, I need to transform the final value of "count" into a global variable. Can I do this?
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Oct 15, 2013
I want to store few different functions to a variable for different structs/classes and then call it later using that variable, is it possible? something like
struct item {
int ID;
int special; // for function
};
item Key;
Key.special = UseKey(KEY_KING);
// now when I want to call function "UseKey(KEY_KING)" I want to use "Key.special", like this
if(iCurrRoom == ROOM_KING)
Key.special;
else if(iCurrRoom == ROOM_DRAGON)
Fireball.special;
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Feb 3, 2014
I've been experimenting with pointers and am getting the below error.
'error: cannot convert 'int**' to 'int*' in assignment'
I thought it was ok to assign a variable address to another variable. Line 18 is where I get the error.
I am trying to show the progression of memory as I increment it as I have done on line 17 and again, I don't know why I don't see a progression through memory locations when output to the console on line 20.
Here's the code:
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
int main() {
int *tt = new int;
int *p = new int;
[Code] .....
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Jun 16, 2013
Any way to create a variable using a variable in the name? So E.g. if you wanted to create an int named nr(x), and x was 1, you would get an int variable named nr1? How would you do this?
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Aug 10, 2014
How to change an enum type variable to a string type variable?
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Aug 5, 2013
Here is the code,
Code:
class A {
};
A& CreateObject() {
static A a;
return a;
} static A aa;
int main() {
return 0;
}
So is there any difference between a defined in CreateObject and aa?
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Aug 31, 2014
So I have a class object that contains the private member variable spot and the public member function MoveLock. Within MoveLock, is a member variable called numbers that holds the place where a user is on a "lock knob". Now, what I'm trying to accomplish is that whenever the user turns the "knob" in the wrong direction, the position is updated with that current numbers so that the clicks needed to unlock the first state is also updated. But I get these errors:
Error E2096 C:Users...switchtest.cpp 34: Illegal structure operation in function main()
Error E2294 C:Users...switchtest.cpp 39: Structure required on left side of . or .* in function main()
Ultimately, what I have in main() is a piece of what I'm going to implement in a class member function. I'm also thinking about moving the if else statements out of the for and creating a second one for the else portion.
#include <iostream>
#include <windows.h>
#include <iomanip>
using namespace std;
HANDLE inKeys = GetStdHandle(STD_INPUT_HANDLE);
HANDLE screen = GetStdHandle(STD_OUTPUT_HANDLE);
[code]....
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Nov 28, 2013
Is it possible to increment a number but have it print out at a maximum value I assign if it reaches that number? For example, if I have 99 tickets total and only 5 of those tickets are still available, and a person requests 10, how can I give them the 5 available and make sure it doesn't go over the max (99)?
Code:
if (strcmp(word2, "RAFFLE") == 0) {
fscanf(ifp, "%d", &purchased_raffle_tix[p]); //scans purchase
fscanf(ifp, "%d", &person[q]); //scans purchaser
num_raffle_sold += purchased_raffle_tix[p];
available_tix = 99 - last_raffle;
if (available_tix >= 1)
[Code] ....
It would out put with the number of the tickets that the purchaser received:
RAFFLE TICKETS 0 - 29 given to PERSON 22
RAFFLE TICKETS 30 - 69 given to PERSON 209
RAFFLE TICKETS 70 - 95 given to PERSON 123
RAFFLE TICKETS 96 - 99 given to PERSON 211
NO RAFFLE TICKETS given to PERSON 27
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Jul 17, 2014
Code:
#include <iostream>
using namespace std;
void f();
extern int x;
int main() {
[Code] .....
x is declared outside the functions and defined inside main(). Then why this code produces a compile error?
x is already declared so it can be used in f(); and when I call f(), x is already defined. Then why can't f() sets the value of x (in main) to 10?
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Nov 12, 2013
I am writing a console program for a class. I have satisfied the assignment, but I want to clear up what is mostly a cosmetic problem. The program prints a form to the console and places the cursor at a location on the form where the user inputs data. The problem occurs when the user presses the enter key without entering data. The cursor goes to the beginning of the next line. If the user enters data after this, the program functions correctly. I want to know how I can reposition the cursor if the user enters no data.
This is the code that reads one of the values:
Code:
void getHousing(HANDLE screen, MonthlyBudget &inputBudget) {
placeCursor(screen, HOUSING_ROW, ACTUAL_COL);
cin >> inputBudget.housing;
while (!validateEntry(screen, inputBudget.housing)) {
placeCursor(screen, HOUSING_ROW, ACTUAL_COL);
cout << SEVEN_SPACES << endl;
placeCursor(screen, HOUSING_ROW, ACTUAL_COL);
cin >> inputBudget.housing;
}
}
validateEntry checks that the entered value is >= 0 SEVEN_SPACES is a string of seven spaces to cover up the previous entry.
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Mar 6, 2015
I remember that the syntax exists I just don't remember what it is.I want to write a conditional function () prior to main (). in that function I'm using a variable that isn't introduced until main (). How do I let C know that I will be int'ng this function prior to the point where it is going to be accessed so that it doesn't freak out? alternatively is it possible to int the variable in both main() and my conditional function so that it exists? I imagine this would cause an issue because I would essentially be int'ng it twice.
I've done the cursory google searches however I don't think I'm using the correct keywords to get the results I'm looking for. If necessary I would be more than happy to post the code it's just a simple 40 line homework assignment.
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Feb 6, 2013
I'm writing a program to sum up the even numbers in between 1 and 100, using a while loop. At the beginning of my program, I initialize a variable "sum" to 0, and a variable "temp" to 1. Afterwards I enter a loop where I determine if "temp" is even or not, and if so add it to sum. However, at the end of my program, when I print "sum", I get a result of 0. Below is my code.
Code:
#include <stdio.h>
int main(void)
{
int sum = 0, temp = 1;
}
[code]...
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May 6, 2013
I have declared and initialized where needed but keep getting a Debug Error: Variable F is being used without being initialized.
Code:
#include "stdafx.h"
#include<stdio.h>
void Signboard (void)
{
/* This function prints the Signboard onto the output page */
int n;
}
[code]....
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Jan 27, 2013
#include<iostream>
#include<iomanip>
#include<fstream>
#include<string>
#include<cmath>
using namespace std;
int studentdetails_mean();
double standard_deviation();
[Code] .....
its showing Run-Time Check Failure #3 - The variable 'mean' is being used without being initialized.
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