C++ :: How To Allocate Memory When It Comes To Using Templates
Oct 25, 2013
I'm currently learning templates -- & my logic is in a knot with what I am trying to do which is the following:
-Create a function name load
-Accepts a filename (the filename is a text file of integers)
-Open the file
-Create an array(dynamically allocating an array) filling it with the elements read in from the file & returns the array(so that the return type of the array is a pointer to the element type of the array).
//Header file:
#ifndef BUBBLE_SORT_H
#define BUBBLE_SORT_H
#include <iostream>
template <typename T>
void load(std::string filename, T *&arr, int *size);
[code].....
how to allocate memory when it comes to using templates..
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Nov 8, 2013
I am trying to make a function that allows me to allocate memory to a "mem" variable and setting each of its chunk's status to FREE. FREE is defined as 0. Below is my code of the function.
Code:
int allocate(mem *mm, int num_chunks, int chunk_size) {
int i;
mem *temp;
if((mm = (mem *) malloc((num_chunks + 1) * chunk_size)) == NULL){
perror("Failed to Malloc
[code]...
mem; If my function works the way it should, it should print out five 0 because that is how I set them in the function, but this is not the case. I've looked at my function for 2 hours, but I could not figure out any logical error. Now, I think my problem lies with my limited knowledge of pointer arithmetic. On the other hand, when I insert 1000 as the second argument into my function, it gives seg faults, which is not the case for smaller values like 5, 10, 15, etc.
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Jan 13, 2013
what i want to do is if memory allocation fails it display a message shown in the example but its not working
vehiptr = new VEHICLE[vnum];
if(vehiptr == 0)
{
cout<<"Failed to Allocate Memory"<<endl;
return main();
}
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Mar 8, 2014
I’m writing an application for raw image processing but I cannot allocate the necessary block of memory, the following simple code gives me an allocation error.
double (*test)[4];
int block = 32747520;
test = new double[block][4];
off course with smaller block size (i.e. int block = 327475;) it works fine. Is there an allocation limit? How it is possible to deal with big blocks of memory?
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Sep 24, 2014
I CANT use std::string, classes, constructors for this project. I am required to use this archaic method of c-style strings with dynamic memory allocation occurring outside the struct.. i know its not the best way to go about this, but there's nothing i can go. I have a struct:
struct card {
char *suit;
char *rank;
int cvalue;
}
I've created a pointer of size 52 for my deck
card *deckPtr = new card[52];
card *deckHome = &deckPtr[0];
I then try to use
for(int i=0;i<52;i++) {
(*deckPtr).suit = new char[8];
(*deckPtr).rank = new char[7];
deckPtr++
}
deckPtr=deckHome;
I am essentially trying to fill in these arrays from a card file, but I cannot make it past running the program, i get sa seg fault which I dont understand why.
I dynamically allocate memory in my card read in function..
void cardInit(card *deckPtr) {
card *deckHome = &deckPointer[0];
ifstream fin;
char *finName = new char[13];
cin >> *finName
fin.open(finName)
[Code] ....
Its a pretty simple program..and my dynamic memory works for the file name, but I cant figure out why it doesnt work for structs?
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Nov 5, 2014
There is a part in the lesson that explains how malloc is used to allocate free memory to a pointer and gives us 2 examples:
Code:
float *ptr = malloc( sizeof(*ptr) ); and Code: float *ptr;
ptr = malloc( sizeof(*ptr) );
From my logic in the first case we allocate the memory to *ptr and in the second to ptr.
It's a bit confusing, am I missing something?
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Jun 13, 2014
Consider this program:
Code:
// sb_string class v1.04
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct sb_string {
[Code] ....
And here is the output I got:
Code:
[harshvardhan@hari-rudra] ~/Desktop% gcc49 -o test test.c
[harshvardhan@hari-rudra] ~/Desktop% ./test
-before Value of len = 1
(in_function)-before Value of len = 1
(in_function)-after Value of len = 1
-after Value of len = 1 I was trying to make a little easier to work with string. Once the memory is allocated by malloc via sb_init() function, the sb_massacre function wasn't working to deallocate the memory. I had used multiple versions of gcc and clang but the result is same.
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Aug 30, 2013
So my assignment is to create a program that calls for a function in main that dynamically allocates an array[3] and then have pointers with multiple levels of indirection and pass them by reference so they are not lost after the function. Here is my code:
#include <iostream>
#include <array>
#include <iomanip>
#include <string>
[Code]....
Next part is to ask user for two non-negative numbers and then get the length of those numbers and create an array. for the size of each number they input. Then to separate those numbers and add the cross-sums.
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Jan 2, 2013
A special hardware unit with some storage in it is connected to your computer and is memory-mapped so that its storage is accessible in the address range 0x55500000 – 0x555fffff. You want to interface this hardware unit to your C++ program so that dynamic memory is allocated in this hardware unit, not in your computer’s memory. Implement a class MyHardwareMemAllocator which has the following function.
void * allocMemoryInMyHardware(int numberOfBytesToAllocate);
which returns a pointer to the allocated memory chunk, or null if unable to allocate.
C library calls like malloc are not allowed.
1) How to allocate memory from given address range.
2) How to check whether this required memory space is available or not for allocating
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Apr 9, 2012
I use the array of Radiobutton,string,.. in my project. How i can destruct these array from memory,because i see the stackoverflew exception.
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Jan 24, 2013
I created a structure containing two variables of type char.
i.e. char name[64],char details[128];
And a pointer to structure now when I write this name and details to file and now I want to change the particular name.
i.e. To modify then if the stored file name is greater than the entered name then it is erasing the next record line also I need to allocate some memory.
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May 11, 2012
I have a question about the KLU library for LU factorization of sparse matrices. The KLU library accepts a pointer to a memory allocator function, by default it is malloc(). Then it uses this pointer to allocate the memory required.
I want to extend the library and I now have object of classes. I want to use the operator new instead of malloc to allocate the memory. In the same time I want the new operator to call the constructors of the objects. Is there a way to do it?
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Dec 15, 2013
Let us consider the following two classes:
class case1
{
public:
int n;
float x;
[code]....
Now, let's suppose that I instantiate an array of 100 elements of each class:
case1 c1[100];
case2<20> c2[100];
My question is this: will c2 occupy roughly half of the memory than c1?will the value c1.n be allocated 100 times, while the value c1.n wil be allocated only once?
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Apr 24, 2013
When you have constant arrays, they are stored in the programme memory space. Upon execution, they are copied into the data space for easy access. To save space in the data space, it is possible to stop it from being copied. Some compilers will deal with this by just specifying the array as const, g++ has a type modifier called PROGMEM.
In any case, the problem is that I'd like to generate some data, preferably without using an external programme to do it. Hence, my question using the template system. Now I could possibly use macro metaprogramming via boost instead of template metaprogramming, and I may have to go that route. However there are limitations, especially since its numbering system is only equivalent to an unsigned byte, which I possibly could use, but could become more messy than if I use the template system that has long long types as well as a whole slue of type safety mechanisms.
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Oct 4, 2014
I'm currently learning the Qt framework and doing my first tutorial. Straight away I saw something that baffled me:
notepad.h
Code: namespace Ui {
class Notepad;
}
class Notepad : public QMainWindow
[Code] ....
Note the ui pointer and the heap allocation in the class constructor; I can't wrap my head around why one would do this. What's going on here?
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Jul 26, 2014
I know I can allocate it this way, on the stack:
char* str[5];
for(i = 0; i < 5; ++i) {
str[i] = new char[STR_SIZE];
}
But if I want to allocate array size through 'new', what's the syntax for that?
I thought this might work, but it gives error: "Initialization with {...} expected for aggregate object"
char* newString[] = new char[5][ARRAYSIZE];
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Aug 31, 2014
Write a program that dynamically allocates an array large enough to hold a user-defined number of test scores. Once all the scores are entered by the user, the array must be passed to a function that sorts them in ascending order. It must use another function that calculates the average score. The program should display the sorted list of scores and average with appropriate headings. The program must use pointer notation instead of array notation. Validation: Do not accept negative numbers for test scores; keep prompting the user for a new grade. Do not accept negative numbers for the number of scores the user wants to enter.
#include <iostream>
#include <iomanip>
using namespace std;
// Function prototypes
double getAverage(int*, int);
void sortScore(int *,int );
[Code] ....
I have no errors in my code but when i run it and i enter a positive interger it just goes into a loop to enter a positive number.
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Mar 29, 2012
In the code below:
void test(int * i) {
i = new int;
*i = 10;
cout << "i: " << *i << endl;
[Code] ....
The outuput is:
i: 10
t: (some memory position).
If I really want to allocate an integer variable to t, i need to modify the void test(int * i) procedure to void test(int *& i).
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May 17, 2012
I have the following code:
Code:
unsigned int bh = 3;
unsigned int b= 2*bh+ 1;
float s[b];
I get the following 3 compilation errors:
error C2057: expected constant expression
error C2466: cannot allocate an array of constant size 0
error C2133: 's' : unknown size
I am using Visual Studios 2010. What is wrong?
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Sep 22, 2012
I'm learning now linked list and dynamic allocate. I don't know how can I answer the program writing exercises.
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Jan 31, 2013
i don't understand why this program crash if i'll insert a number more of 5 times... i want to allocate dynamically a vector if the input of the user exceeds 5 times... this is the code:
Code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int * vettore, n;
unsigned int len=1;
}
[code]....
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Jan 22, 2013
Some reading through C++ code I come across template deceleration without any type , I have tested the code it compiles too
Code:
template<>
class abc {
}
similarly template usage
Code:
abc<> a;
example of such usage can be found here [URL] ....
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May 27, 2014
I decided to make a linked list program using classes and templates.I implemented my linked list and added some basic functions, everything worked just fine. Then I proceeded to add templates...First, the error list:
#pragma once
template<class T>
class Node {
private:
Node* next;
[code]....
To sum up: Something's wrong with the templates that I used in "List.cpp" and what it could be.
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Mar 14, 2013
After asking the user to input 2 values i expect my program to read them and then output whether they are equal, bigger or smaller than one another. However i am getting no output what so ever when i input the values
code below:
#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
#include <string.h>
using namespace std;
int intInput1, intInput2;
float floatInput1, floatInput2;
int x, n;
[Code] .....
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Aug 26, 2014
Why wouldn't this code compile when adding '<double>' after the function call?
template<class T>
T add(T& a, T& b){
return a + b;
}
int main() {
int a, b;
cin >> a >> b;
cout << add<double>(a,b);
}
Compiler error:
cannot convert 'a' (type 'int') to type 'double&'
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Feb 25, 2013
How templates are implemented internally?
Theoretically templates are nothing but a generic routines. But how it has been implemented internally?What complier exactly does?
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