C :: Allocating Memory To Array Of Struct?
Sep 9, 2013Do you have to allocate memory(malloc) for an array of structs? Example:
Code:
typedef struct{
char * name;
}First;
struct name{
First fname;
};
struct name Names[10];
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C/C++ :: Allocating Memory For 2D Array In Other Class?
Jun 10, 2014I'm making some multi-threaded program, but thats not my problem as i've done that already. I have a class with user-functions containing a structure which then contains a two dimensional array for each user with 25 elements. So I dont want to limit the user and make the array for example with just 10 rows, but allocate the needed memory to match the amount of 'users' a potential user of my program would want. The problem is, that i know how i should allocate it using 'new int' but it just doesnt work ! It gives an error:
Error: no operator "=" matches these operands
UserStuff.h:
struct userDataStruct {
bool* isAdmin;
[Code]...
Then, in some completely other class function inside the file mentioned above: (I know i could do a function in CUsers class which could allocate the memory, but I have this function which is used for some other things and it already has the amount of max users
void OtherClass::somefunction(maxusers)
{
// This gives an error: Error: no operator "=" matches these operands
curUsers->uData.userNumbers = new int*[maxusers]; //maxusers is the int variable of max users specified by the client
// However this doesn't
for( int i = 0 ; i < maxusers ; i++ )
curUsers->uData.userNumbers[i] = new int[25]; // 25 columns, this doesnt give any error
}
I'm not really sure what I'm doing wrong. Doing this in some function from CUsers class works (without curUsers-> or with, doesn't give any error) but doing it from some other class's function doesnt.
C++ :: Allocating Memory For Vectorized 2D Array?
Mar 2, 2015I want to be able to dynamically allocate and index an array like the following: vv2d[1][2].x and vv2d[1][2].y. In order to accomplish that I have chosen to use a std::vector of a std::vector of a 2D point class.
Code:
/// Here is my templated version of a 2d point class which I have adopted from
/// one by Alexander Chernosvitov, Function Graphics, 2001 (see ogview.h)
/// http://www.codeguru.com/cpp/g-m/opengl/article.php/c5581/Function-graphics-in-3D.htm
template <typename T>
[Code]....
Boundary violation occurs as soon as vv2d[1][0].x is encountered. I believe the problem is my inability to dynamically allocate the size of the (primary) typedef vector. However, eliminating the typedef for the following does not change the result. Further examination shows the vv2d[1][0] size and capacity to be 0.
Code:
vector<vector<CPoint2D<double>>> vv2d;
vv2d.resize(3);
vv2d[0].resize(3);
C :: Allocating And Freeing Memory For Array Of Structures
Jul 27, 2014I have to allocate memory for an array of structures, and my structure looks as following:
Code:
typedef struct {
char *name;
Uint *start_pos;
Uint len;
}
example_struct;
And now I want to allocate memory, for a variable number (so an array) of example_struct, so I first do:
Code:
example struct *all_struct;
int total_num = 3;
//will be set somehow, but for the example I set it on 3 all_struct = malloc (sizeof(example_struct) * total_num);
And now, as far as I now, I will have to allocate for each field of the structure memory, in order to be able to use it later. But I have problem at this point, a problem of understanding:
- I just allocated memory for 3 structures, but don't I have to allocate then memory for each structure separately, or can I just now allocate the fields like this:
Code: all_struct[0].name = malloc.....
But if yes, why the hell this works...
C :: Dynamically Allocating Memory?
Sep 18, 2013I have created a database for music cds:
Code:
#include<stdio.h>
#include<stdlib.h>
#define array
typedef struct cd_database
[Code]....
When I am using malloc instead of arrays the code is not working properly after exit. I have tried alot but can't came up with a way
C :: Error Allocating Memory
Jun 1, 2014Code:
# include <stdio.h>
# include <math.h>
# include <stdlib.h>
# include <malloc.h>
}
[code]...
I am compiling it on a 64 BIT ubuntu machine having 64GB ram using gcc 4.6 compiler. I am getting the following output Error allocating memory. But (914*866*2724) is approximately 8 GB, Whats wrong with the code?
C++ :: Not Allocating Enough Memory To Pointer?
Jan 24, 2014I wrote the following C++ constructor, and I get an error - BUFFER too small on strcpy_s
Trace::Trace(const char *str) {
if (str) {
int len = strlen(str);
this->m_name = new char[len+1]; // asking for 'len+1' memory elements of char
strcpy_s(m_name, len, str); // **** I get here an error "BUFFER TOO SMALL" ****
[Code] .....
m_name is a private data member of type char* .
C :: Under-allocating Memory For A Tagged Union
Mar 6, 2015What i'm interested in is the behavour of a struct/union constructed like this:
Code:
typedef struct {
uint64_t num1;
uint64_t num2;
} st_a;
typedef struct {
uint64_t num1;
uint32_t num2;
[Code] .....
What kind of behavour could I expect from object, in the following cases:
1. newsomestruct(0)->u.a.num1 = 2;
2. newsomestruct(1)->u.b.num1 = 2;
3. newsomestruct(0)->u.a.num2 = 2;
4. newsomestruct(1)->u.b.num2 = 2;
5. newsomestruct(0)->u.b.num1 = 2;
6. newsomestruct(1)->u.a.num1 = 2;
7. newsomestruct(0)->u.b.num2 = 2;
8. newsomestruct(1)->u.a.num2 = 2;
9. Code:
somestruct* ss1 = newsomestruct(0);
somestruct* ss2 = newsomestruct(1);
* ss1 = * ss2; 10. Code: somestruct* ss1 = newsomestruct(0);
somestruct* ss2 = newsomestruct(1);
* ss2 = * ss1;
This is what I'd expect, but I can't find any evidence online in C standards or elsewhere:
1. Works as expected, sets the value of a.num1 to 2.
2. Works as expected, sets the value of b.num1 to 2.
3. Works as expected, sets the value of a.num2 to 2.
4. Works as expected, sets the value of b.num2 to 2.
5. Works as expected, sets the value of b.num1 to 2.
6. Works as expected, sets the value of a.num1 to 2.
7. Works as expected, sets the value of b.num1 to 2.
8. Crashes/Memory Corruption, attempted to alter memory outside struct.
9. Works as expected, * ss1 == * ss2
10. Crashes/Memory Corruption, attempted to alter memory outside struct.
I've tested simular code on my machine (Xubuntu 14.04LTS compiled with gcc on -O3) and it appears to be reliable, given that you stick with acessing the type tagged in the struct or the common initial union struct members (in this case num1).
C++ :: Integer Pointer - Get Address Without Allocating Memory
Jun 3, 2013I have an integer pointer and i want its address without allocating memory,
main() {
int *a;
cout<<a;
}
This is giving 00000000 and its but obvious. Now if i use address of a (&a) along with *a,
main() {
int *a;
cout<<a;
cout<<&a;
}
'cout<<a' gives me a constant address but 'cout<<&a' gives me different address.
what is the reason behind & and why behaviour of 'cout<<a' changes when using with &.
C++ :: Allocating Array Of Pointers To Dynamically Allocated Array?
Jan 18, 2014I'm trying extremely hard to understand pointers and I have the basic concept down.. I feel as though my knowledge of dynamically allocated pointers and pointers in general is not enough to understand the logic behind what I'm trying to do. The problem is that the donations array must be able to accept any number of donations. I've made it do just that, but there is also an array of pointers which must each point to the same element in the donations array. The program works if I assign int *arrPtr[100] for example, but it does not work if I try to dynamically allocate it to accept the same number of elements for donations entered by the user. Here it's the snippet
#include <iostream>
using namespace std;
//Function Prototypes
[Code]....
C++ :: Dynamically Allocating Multidimensional Array?
Nov 24, 2013Working on this one from the Jumping into c++ book. The book asks that I create a multidimensional array at run time based on user input and fill it with a multiplication table
My code compiles fine but throws an uninitiated error for p when I try and run it.
Code:
void multiDimentionalMultiplication(int x, int y, int z){
int ***p;
**p = new int[x];
std::cout << "Allocating array.
[code]....
C++ :: Dynamically Allocating One Dimension Of 3D Array?
Jun 14, 2013I am trying to figure out the syntax to dynamically allocate a single dimension of a triple dimensional array. Basically i have a 2D array of structs. but each struct is an array (basically rows of the information). The rows of this structure need to be allocated dynamically, but the height and width of the overarching structure are static.
Basically: Struct * ts_FieldInfo[100][100] = new Struct[Class.returndataitems()];
C++ :: Allocating Number Of Element On Array
Mar 7, 2013#include <iostream>
using namespace std;
int main() {
int elm = 0;
int size = 0;
int *array;
[Code] ....
C/C++ :: Dynamically Allocating Pointer Array
Apr 15, 2014so I have this code that dynamically allocates a pointer array increasing and removing elements of the array as its operated on.then it sorts and prints out the array when the user is finished operation on the array. i get this error message when running the program though.
"Unhandled exception at 0x0F474F98 (msvcr110d.dll) in Lab10_VarArray.exe: 0xC0000005: Access violation reading location 0xCCCCCCC0."
this is my code
#include <iostream>
#include <cstdlib>
#include "Header.h"
using std::cout; using std::endl; using std::cin;
int main(void) {
char op='x';
[Code]...
C :: Segmentation Fault When Dynamically Allocating 2D Array
Apr 20, 2013This is a homework assignment where I have to read a file into a dynamically allocated 2d array. The file format is
10
Jim 3.6
Jake 4.0
Will 3.0
Sara 3.4
Mike 2.5
Ellen 2.9
Melissa 3.9
Eric 3.8
John 3.5
Beth 3.9
where 10 is the number of students followed by the students and the gpa's. There is more to the program but I have not implemented it yet because I am getting a segmentation fault. The output I am getting when I print the array is
Jim 3.6
Jake 4.0
Will 3.0
Sara 3.4
Segmentation fault
I can see where the problem lies. If I raise value for row when I am allocating the rows of the array, all of the names print. I just do not see why I need to. From my understanding the row * sizeof(char*) should give me enough room for 10 entrie.
Code:
#include <stdio.h>
#include <stdlib.h>
void sort();
int main()
[Code] .....
C/C++ :: Dynamically Allocating Array Passed As Parameter
Apr 18, 2015I'm trying to dynamically allocate a standard array at runtime in the function of a class where the array is "owned" by the calling class. The calling class knows nothing about the array before it makes the call to create the array other than the datatype of the array. But the full array of data needs to be returned.
It appears that the pointer being passed makes a copy of the pointer on the stack and then when the function returns it pops it off the stack and the array is a memory leak because the pointer is once again a nullptr as it was before being passed and the array has not been deallocated with delete yet (as it should not have been).
(Edit:Unexpected value of MyArray being a nullptr instead of pointing to an array after returning from line 09.)
class Class1 {
void FunctionA() {
Class2 OwnedClass;
int* MyArray = nullptr;
int SizeOfMyArray = 0;
[Code] ....
C++ :: Dynamically Allocate Memory To Struct
Sep 24, 2014I 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?
C :: Shared Memory / Cannot Read Last Element In A Struct
Jun 27, 2014I have trouble reading the last element in a struct.I do get the correct value for the first two elements. In my example that is:
a = 11 and c = H
however I get:
b = 0
but I am expecting b=2
I got two files to handle this.The first one is writing data to memory -
Code:
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
}
[code]....
why I cannot get correct value for the third element in my struct?In the second file where I'm reading from memory I allocate some space. Is this incorrect in some way? I'm running this on a Linux machine.
C :: Parsing Char Array To Array Of Struct To Process Packets
May 28, 2013I wrote this simplified version of a program i am writing that parses data in UDP packets. In the process of doing so i pretty much answered all my questions and fix all the problems i was having.
decodeSystemMap function will be in loop, and will proccess packets that have mostly the same data, only a few items will be added or changed or deleted.
whats the best way to check if there are any new, deleted, or removed items in the packet and only modify those?
Is there anything unsafe / dangrous about the way the code is now?
Code:
/* * File: main.c
* Author: david
*
* Created on May 23, 2013, 11:57 AM
*/
#include <stdio.h>
#include <stdlib.h>
[Code] ....
C++ :: Allocating Space Only For Two Characters
Jan 15, 2013I am allocating space only for two characters but it fits all of them, if you run this it will print the whole string literal "hello my friend". How is that possible?
I am using gcc 4.6.3., I know about strncpy().
#include<iostream>
#include<cstring>
using namespace std;
int main(){
char* str = new char[2];
strcpy(str, "hello my friend");
cout << str << endl;
return 0;
}
C++ :: Declare Not Allocating Storage?
Jan 22, 2014decalration won't allocate storage, while definition will. This is a test program:
#include <iostream>
using namespace std;
extern int ei;
int i;
[Code].....
Others are all fine in this program except ei.
compiler error: undefined reference to ei.
I understand ei is only declared so there is no memory address, but when I do ei=1, then ei completed it's definition, why still cannot use pei to get it's address?
C :: Array Of Pointers To A Struct?
May 10, 2013I am working on an assignment identical to another post from a couple years ago, for reference here is the thread:
array of pointers to structures sorting addresses by zip code
They way it is written on that thread is almost identical to the way the teacher implied to have it done (only wrote part of the input block). But I am having an error:
When it gets to the output section it outputs then next name along with the zip code... I tried strncpy and strxfrm but both cause more problems than they did work.
The last part of the project is to have the output put out in order of least zip code to most zip code (00000<99999), so this is causing me a real problem and I do not see what exactly is making this happen.
Here is my code (we dont HAVE to use gets but professor suggested using it for this assignment, next lab is to rewrite this using files and fgets rather than I/O redirection):
header.h Code: #ifndef lab_6b_7b_Header_h
#define lab_6b_7b_Header_h
//header file intiating other headers
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct{
[code]....
I have not started the sorting code because I cannot get past this, but once I have proper zip codes I am sure I can make a sort function no problem.
I am using xcode with some breaks to read variables as various points and do not notice anything wrong until it makes it to the output functions, although this page briefly pops up between input and output functions when the breaks are up:
C :: Passing Struct Through Array
Apr 2, 2013I am trying to pass a struct through an array to another array from one microprocessor to another microprocessor and then dereference that array to update the same exact struct on the other microprocessor.My goal is to always have values inside of both structs while sending any updates to the struct on the other microprocessor in the mean time but I seem to be looping through the data and the members of the struct seem to be cleared out after every clock cycle. I can verify this by the flashing of my leds which the struct controls.
FIRST MICROPROCESSOR
Code:
extern struct i2c_data * TX_Data;
extern struct i2c_data TX_Data_1;
extern struct i2c_data TX_Data_2;
}
[code]....
C++ :: Array Of Struct Initialization
Apr 4, 2014In a book I'm reading, the author has the following struct:
struct VertexPos {
XMFLOAT3 pos;
};
Where XMFLOAT3 is a structure with x,y,z floating point values within. He declares and initializes an array as the following.
VertexPos vertices[] =
{
XMFLOAT3(0.5f, 0.5f, 0.5f),
XMFLOAT3(3.3f, 5.6f, 3.6f),
XMFLOAT3(-4.5f, 2.2f, 6.4f)
};
It doesn't make sense to me why this is working. The way my mind is thinking about this is that vertices is an array of type VertexPos, so then why can it be initialized with objects of type XMFLOAT3?
C++ :: Length Of Array Of Struct
Jan 23, 2015I'm trying to make an application and I need the length of the array of a struct. Like this:
struct myStruct {
int integer;
};
myStruct struct[] =
{
1,
2,
};
I want to get how many ints are in the array...
C++ :: Reading A File Into Array Of Struct
Nov 20, 2014Code:
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
struct inventory
[Code]...
This is my program output Enter the file name : "filename".txt ..... (Nothing shows up)