What is the difference between initializing pointers to a memory address using the address operator like int *pointer = &x; or initializing it to a value like int *pointer = x; .. in other words how does p and q point to the same memory address in:
const int ARRAY_LEN = 100;
int arr [ ARRAY_LEN ];
int *p = arr;
int *q = &arr[0];
I have this struct declaration to create a linked list
struct node {
string y;
node* next;
};
If I create a linked list of 3 nodes
A->B->C->NULL
A->y is "a"
B->y is "b"
C->y is "c"
Since they are consecutive in memory. How far apart are the strings in memory?
I tried doing something like
int n = &(head->next->x)-&(head->x);
The problem is that I got 6 while debugging and 2 otherwise.
My project is say that it has memory leaks. When I view it in the debugger, it shows the correct values being passed to the pointers.
Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
bool ConfigGetEntry( char *pcFile, char *pcNameMust, char* &pcResult ) {
char pcBuffer[ 512 ];
[Code] ....
Its saying that i have memory corrupting at..
Code:
if ( !ConfigGetEntry( pcFile, pcName, pcRet ) ) return _strdup( pcDefault );
Also is it normal to have a bad pointer then point data into it to then clear that of the bad pointer. To have valid data now in that pointer.
Jumping into C++, question 5 page 181:
"Write a program that compares the memory addresses of two different variables on the stack and prints out the order of the variables by numerical order of their addresses.
Does my solution look correct
Code:
#include <iostream>
using namespace std;
int main() {
int one = 1;
int two = 2;
if (&one < &two)
cout << one << " " << &one << " " << two << &two << endl;
else
cout << two << " " << &two << " " << one << " " << &one << endl;
}
My question is this: Is it possible to determine where functions are stored at compile time, so that at run time you can pass the memory address as a pointer to the interrupt handler so that it can directly call the function at memory location 'X'?
The newest project I'm working on would require to either somehow capture these addresses or to find a work-around so that instead of passing the pointer to the interrupt handler, the software would then need to be able to be non-interruptable.
the question is; Write a program that prints out the memory addresses of each element in a two-dimensional array. Check to see if the values printed out make sense to you based on the way I explained it before.
Below is the code I have done. I am having problems printing the "-" sign to keep formatting with the board when the user enter in different dimensions other than [4][4].
Code:
#include <iostream>
using namespace std;
void printTable (int x, int y) {
int **p_p_twoDimension = new int* [y];
for (int i = 0; i < y; i++) {
p_p_twoDimension[i] = new int [x];}
[Code]...
I'm learning OpenGL using the C API and some of the functions' argument types have proven a bit challenging to me.
One example is the function Code: glShaderSource(GLuint shader, GLsizei count, GLchar const** string, GLint const* length); It resides in foo() which receives a vector "data" from elsewhere Code: void foo(std::vector<std::pair<GLenum, GLchar const*>> const& data); To pass the pair's second element to glShaderSource's third argument, I do the following:
Code:
GLchar const* const source[] = {data[0].second};
glShaderSource(..., ..., source, ...);
Now I have two questions regarding this:
1. Can I initialize a char const** via initialization list, the way I do a char const*?
Code:
// this works
std::vector<std::pair<GLenum, GLchar const*>> const shader_sources = {
{GL_VERTEX_SHADER, "sourcecode"},
{GL_FRAGMENT_SHADER, "sourcecode"}
};
// but is this possible?
std::vector<std::pair<GLenum, GLchar const**>> = { ??? };
2. Is there an alternative to creating a temporary GLchar**, even though that's specifically what the function wants?
When i return 0; at the function int userselect (int user, int comp)my output displays twice and when i ask the user to run it again the computers selection of rock, paper or scissors remains the same it doesn't find a new random number. So i made the function userselect return to main(). This works and my output is displayed once, but when i run it it skips my while part of my do while loop completely so it loops the program without asking the user if they wish to run it again.
but when i return main() the computers choice re-randomizes every time so i need to find a way to get the while part of my do while to initialize and the program to not loop without the option of ending it.
#include <iostream>
#include <string>
#include <cmath>
[Code]....
declare
int *p[3];
that gives an array with 3 pointers, but how 3 pointers can have a link in the memory?
Pointers point to an address in memory. What if I used 3 pointers: 2 to mark the first/last nodes, and the third to mark the current node being referenced? I would wrap it in a class (to make the memory management automatic, of course), but is this practical?? maybe some pseudo code will get the juices flowing:
template<class type>
class supercondensed_list{
public:
supercondensed_list();
~supercondensed_list();
[code].....
Any things I should take into consideration? I'm not exactly the most experienced with pointers, and manually managing memory, but I think it's worth trying. If this works, then my programs should, in theory, be 100% memory efficient.
we are currently covering double pointers and memory allocation. Currently getScrabbleWords is not working. when I compile with commented code (Main() works fine) I get a segmentation fault.
This is the purpose of getScrabbleWords:
char **getScrabbleWords(char **allWords, char letters[]):
This function takes an array of char* values (i.e. strings) representing all the words read from wordlist.txt. Each of these words is tested by callingcanWeMakeIt as a helper function, and pointers to the words that can be made are put into an array, myWords. Note, copies of the words are not made! In order to indicate the end of myWords, we terminate with a NULL pointer. Thus, if N words can be made from letters then myWords should have length N+1.
I get a memory access violation when I run the below code. void createNewImage(int width, int height); this function deletes any current image data and creates a new image with the specified width/height and allocates the needed number of pixels dynamically. The new image contains four blocks with different color, red, blue, green, and black.
Code:
#include <iostream>
#include "image.h"
image::image() {
pixels = NULL;
width = 0;
height = 0;
[Code] .....
Suppose I wished to reallocate memory (resize) an array of pointers. Why does the following not work?(The program runs, yet yields a faulty segmentation error message. Why?):
Code: char **ptrarr = (char**) malloc(sizeof(char*))
Code: ptrarr = (char**) realloc(ptrarr, (capacity) * sizeof(char*));
I need to use dynamic memory allocation and use pointers to iterate through the arrays that I have already in this program. I am lost, nothing I do works and where to use the pointers. I am just looking for a push in the right direction so I can finish this project and how I can implement pointers in my program.
#include <iostream>
#include <string>
#include <cstdlib>
#include <iomanip>
#include <stdio.h>
using namespace std;
[Code]...
Having some frustrating issues trying to free memory from a dynamically allocated array of pointers to linked lists. I think the problem is in how I initialize the pointers to NULL. Is there a more elegant way to have the program recognize that the list is empty so it knows to create a head node for the linked list in the function 'add_end_stub_to_array'?
I ran the code through Valgrind and it says that memory is definitely lost from this array.
This is the structure definition.
Code: struct stub_edge {
int loc_id;
int anim_type;
int mkt;
struct stub_edge *next_node;
};
Here is the code snippet from main allocating and deallocating memory to the array.
Code:
struct stub_edge **stub_list = (struct stub_edge **)malloc( sizeof(struct stub_edge *) * 12);
for (i = 0; i < 12; i++)
{
stub_list[i] = (struct stub_edge *)malloc(sizeof(struct stub_edge));
stub_list[i] = NULL;
}
stub_list = add_end_stub_to_array(end_stubs, stub_list);
destroy_end_stub_array(stub_list);
Here the function for adding nodes to the lists by reading through a dynamically allocated 2D array. (The end_stubs array is ordered by month and each linked list represents events occuring within the month).
Code:
struct stub_edge **add_end_stub_to_array(int **end_stubs, struct stub_edge **list)
{
long int i = 0;
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
int break1 = 0;
while(i < num_edges && break1 == 0 && mon < 12)
[Code]...
Here is the function for freeing memory from the list.
Code:
void destroy_end_stub_array(struct stub_edge **list)
{
if(list != NULL)
{
int mon = 0;
struct stub_edge *current_node1;
struct stub_edge *new_node1;
for(mon = 0; mon < 12; mon++)
[Code]...
This function below takes a pointer as an argument. What I expect to happen is, since expr++ has higher precedence than *expr, that is, the primary expression operators have higher precedence than the unary operators, pointer arithmetic should occur where we increment to the second address pointed to by dbuf, and then we should dereference the value at that address. Given that logiv, when i print dbuf[3] it should print the value pointed to at the 4th address in dbuf. However, the value it returns is 0x0 not 0x3. Why doesn't it dereference the value 0x3?
Code: void dfill(unsigned char *dbuf)
{
dbuf = (unsigned char*)malloc(4);
memset(dbuf, 0, 4);
*dbuf = 0x0;
*dbuf++ = 0x1;
*dbuf++ = 0x2;
*dbuf++ = 0x3;
printf("dbuf val: 0x%x
", dbuf[3]);
}
I have a school project where I have to create a class with 2 attributes that default to 1. To verify that they are at 1, I have a cout before any user inputs or value manipulation. It works for the most part. What happens is that if I change the defaults to 17, the cout will retain the old values until I have an unsuccessful build (remove a semicolon from the end of the line). When I have a successful build (put that semicolon back), the cout displays the changed values. Change the values back to 1 and the same thing happens again until I have an unsuccessful build then a successful build. Are the old values getting stuck in memory somewhere?
// Rectangle.h
// Chapter 9_Problem 9.11_Page 412
#include <iostream>
using namespace std;
#ifndef RECTANGLE_H
#define RECTANGLE_H
class Rectangle // Rectangle class {
public:
Rectangle(double = 17, double = 17); // default constructor setting values to 1
[code]....
The problem may only apply to VC++ compiler - ??.
Cannot do this:
const unsigned int Port = 0x900E0000;
unsigned int *pData = Port; //Error - can't convert from int to int*.
Solution:
const unsigned int PORT = 0x900E0000;
const unsigned int PORT_PTR = ((unsigned int *)0x900E0000);
unsigned int *pData = PORT_PTR; //No Error.
I found no way to do it but the above.
Ex., you cannot do:
pData = (unsigned int *)0x900E0000;
I'd like to do a MergeSort with sentinels and order the pointers, not the values!
#include <iostream>
#include <limits>
using namespace std;
void
stampa (int *n) {
int i;
for (i = 0; i < 10; i++) {
[Code] .....
I create some code that assign values to a dynamic memory structure. I'm not sure why one code works and the other crashes when it assigns a value.
Working Code
#include <iostream>
using namespace std;
struct WorldOjectCollisionMap
{
[Code].....
I serialize a XML file, and i have this values here:
public class ServiceConfig {
public List<DatabaseDescriptor> Databases { get; set; }
} public class DatabaseDescriptor {
[XmlElement("Name")]
[Code] ....
I have a form1 which is a datagrid view and get's updated like this:
dataGridView1.DataSource = xmlData.Databases;
Now i have a button: get tables, and it opens up form 2, there it's supposed to appear all the tables of the selected Database, when i click on the row i get the database name so i get all the list of Tables from
DatabaseDescriptor
where
DatabaseDescriptor.Name == name
(I get this when i select the row)
But then on the 2nd form, i also have 2 textbox so i add a new table, i add the tablename and id. the new value should appear in the datagridview of the tables, and when i close it and reopen it, it should be there. Maybe i should concatenate first the values or something, how do i do?
typedef struct example_dt_struct {
int a;
float b;
char* c;
};
typedef void(*func)(example_dt_struct *s, int e, int f);
void f(func *n){}
how can i use example_dt_structure with my function pointer into f()
Which is more efficient in functions? Returning values or using pointers to redefine variables passed as arguments?
I mean either using:
void ptr_Func(int *x)
{
*x = *x+1
}
or
int ptr_Func(int x)
{
return x + 1;
}
In terms of speed, memory use etc.I want to know general efficiency, I know it will obviously vary with different uses and circumstances.
I was wondering if it is possible to check if two addresses, so pointers are equal.I was saving the address of an array, and later wanted to identify it by the address, so if my area has the address: int *my_array; // is equal to: 0x1e9aa3a2c ...Later when I go through a list of pointers like:
list=
0x1e9c7e060
0x1e9ba6640
0x1e9aa3a2c <== my address
0x1e9aa3a2c
I want the third one to be equal to my list, but with == it didn't work for me.
I want to take a starting IP on a local network, and loop through to an ending IP on a local network, pinging all the IP addresses in between. For instance, ping all IP addresses between 192.168.1.1 - 192.168.1.255 (user enters desired starting IP and ending IP in text boxes).
I have the ping functionality working, and i can make it all work with lots of messy string parsing.. but it seems sloppy to me.
I have to split the strings (start and end IP) to get the last octet, then subtract to get the range of IPs. Then loop through, adding 1 to the last octet, and converting back to a string each time.
The C# Ping class can use either a string or an IPaddress for its Send method. If I use IPAddress, I just have to convert it from the text box it originates in, but the adding 1 to the last octet in the loop is a hassle.
Anyway, I guess the only question I have is, if you had to loop through a range of IP addresses, how would YOU do it?
public Job(string ipStartIn, string ipEndIn) {
long ip1 = Convert.ToInt64(ipStartIn);
long ip2 = Convert.ToInt64(ipEndIn);
IPStart = new IPAddress(ip1);
IPEnd = new IPAddress (ip2);
this.deviceAlive = false;
[Code] ....
I'm taking a university course and one of our first projects dealing with C is to write a hash table (with chaining as a collision solution) that will hash loads of hexadecimal values into the table. I'm just brain storming right now but how practical is it to hash the values by converting them to decimal and working with that value in another function to organize the values? I'm thinking this might take a lot of time and memory because our code will be tested with text files that could have a few lines of hexadecimal addresses or millions of them.
View 2 Replies View Related
