C++ :: Memory Allocation With Sprintf And Strcat For Reading 1-Wire Device
Mar 9, 2012
I'm using a uC to read the device ID from a One Wire device. I'm trying to have the ID read every second and output to over a USART serial stream for debugging, however I'm having a number of problems getting this to work correctly and I think it has to do with my misunderstanding of memory allocation in this case.
The problem is that when I upload the binary to the uC, it gets the device ID correctly the first time, and from thereafter the program is unstable and starts returning garbage (1st screenshot).
Ideally everything inside of the while loop would be inside of its own function, however I have had nothing but trouble doing that. In fact, when I put that all into it's own function that returns void and takes BUSES as an input, the correct data comes out the first and therefore it somehow exits the "while" loop and never gets back in (2nd screenshot). Another thing I noticed is that when I put the variable declaration outside of the while loop in the code below, I get the same behavior.
I haven't include the code for OWI_DetectPresence and OWI_SendByte ... I've hooked up an oscilloscope and have visually confirmed they are working correctly. Once the OWI_ROM_READ byte is sent over the bus the slave responds with it's device ID. I feel like my issue here is memory allocation and not hardware.
how to fix the issue with the output to USART and how to make this into a function that returns the string of the hex ID?
Code:
int main(void) {
unsigned char OWI_on_bus = FALSE;
// initialize UART for debugging
Init_USART();
[Code].....
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Jul 14, 2013
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Code:
int *p, ar[100];
p = (int *)malloc(sizeof ar);
.. *p is a pointer variable, but what means another * here --> (int *)?
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I am trying to allocate a memory to vector but while running the program,my window appear and PC get halt state then i have to force fully shutdown my PC I found that due to the vector i am getting this problem.
#define SCOPEPLOT_MAXNUM_SAMPLES (1000000)
QHash<int, std::vector<double>*> m_sampleHash;
m_sampleHash.insert(1, new std::vector<double>(SCOPEPLOT_MAXNUM_SAMPLES));
std::vector<double>* vec_p = m_sampleHash.value(1);
for(int k = 0;k < numSamples;k++)
{
count++;
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Apr 15, 2014
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vector<Type*> vect; //vect will be on stack and Type* will be on heap.
What I would like to know is, are all of the above statements true?
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Jul 13, 2014
1) int *a=new int[10]
2) int a[10]
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Dec 18, 2013
Here is my code:
Code:
class Base {
};
class Derived1 : public Base {
};
class Derived2 : public Base {
} class Bar {
public:
void SomeFunc();
[code].....
MSVC2010 throws out compiler error which says:
Code:
no operator found which takes a right-hand operand of type 'Derived *' (or there is no acceptable conversion)
What I don't understand is why? The pointer is an address of 0 element of an array. So what is the problem? I can eliminate the error by using double pointer but it will be an overkill.
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Feb 24, 2014
I have recently bought a copy of "Jumping into C++" and have come to chapter 14 ( dynamic memory location) and have a question.
On page 153-154 an example of dynamic allocation is given for array's of int. How would the code look like for strings or structs ?
The allocation was given by:
Code:
int *growArray (int* p_values, int *size)
{
*size *= 2;
int *p_new_values = new int[ *size ];
for ( int i = 0; i < *size; ++i )
{
p_new_values[ i ] = p_values[ i ];
}
delete [] p_values;
return p_new_values;
}
Sample Code I tried to use this for an array of structs but failed completely....
I used the following struct Code:
struct user{
int days;
string name;
};
and the allocation function (which does not work):
Code:
struct user *growarray (struct user *p_values, int *size) {
*size *= 2;
struct user *p_new_values = new struct user[ *size ];
for ( int i = 0; i < *size; ++i )
[Code].....
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Jul 3, 2013
I am creating a connect 4 game using dynamic memory allocation the question is;
Write a two-player game of Connect Four where the user can set the width and height of the board and each player gets a turn to drop a token into the slot. Display the board using + for one side, x for the other, and _ to indicate blank spaces.
I have created the board. However I am unsure as how to make a start on getting the players to make moves.
Code:
#include <iostream>
using namespace std;
char **create_table(int width, int height, char blank) {
char **p_p_connect4 = new char*[height];
for(int i = 0; i < height; i++) {
p_p_connect4[i] = new char [width];
[Code]....
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Jul 11, 2013
Small code to show overflow...But when I compile and run - buffer_one is not being overwritten when the byte size of buffer_two overflows .
Code:
#include <stdio.h>#include <string.h>
int main(int argc, char *argv[]) {
int value = 5;
char buffer_one[8], buffer_two[8];
strcpy(buffer_two, "two"); //Put "one" into buffer_one
strcpy(buffer_one, "one"); //Put "two" into buffer_two
}
[code]....
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Apr 17, 2014
I'm having problems with this code:
#include <iostream>
using namespace std;
class Foo {
public:
Foo( int n );// Constructor
~Foo();// Destructor
int *ptr;
int N;
[Code] ....
I'm using Visual C++ 2008 version. The problem arises at the end, after the sentence 'system("pause")' is reached, which makes me think that the problem happens when calling the destructor. The destructor is called twice, the first time it's called is in the function print. The problem seems to be that the destructor can only be called once.
I know I can avoid this situation by defining the function print like this:
void print ( const Foo &f )
...
but I would like to know if there is some way I can do this keeping the definition that I've provided.
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Dec 27, 2014
I've been working on a matrix class and I ran into a problem in writing my matrix class. I keep getting 0 as a determinant and with some debugging, I found that I was losing allocated data or something similar. This algorithm I'm pretty sure works because I used this same algorithm in a function I made in python. [URL] .... That's where I found the algorithm.
/*template <class T>
double Matrix<T>::det(T* array, size_t dim, bool recursion)*/
double det(T* array = NULL, size_t dim = 0, bool recursion = false) {
if (recursion == false) {
if (m != n) {
return 0;
[Code] .....
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Aug 7, 2013
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typedef techsoft::matrix<double> dMatrix;
dMatrix A(nDataPoints, numCol);
dMatrix z(numCol, 1);
dMatrix b(nDataPoints, 1);
dMatrix (nDataPoints, nDataPoints);
nDataPoints and numCol are globally defined integers which get the values 120 and 13 (just about the size of those matrices).
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return HeapAlloc(_crtheap, 0, size ? size : 1);
(in malloc.c).
This program debugged without any problem with same code - now I just edited the size of the matrices. And I tried the same with another library called "Eigen" and I get the same problem - so I guess there is a problem with the heap and I have to do some kind of memory allocation...
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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[]):
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Why cant a dynamic memory allocation work with references? I was told that references work with const pointers deep down so shouldn't this be legal code?
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unsigned char* dataBuffer2 = (unsigned char *) (pci_buffer2.UserAddr);
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double* Rin = new double[length];
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Jun 17, 2013
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Code: #include <iostream>
using namespace std;
char SQAURE_CHAR = {' '};
const int Board_Size = 14;
[Code] ....
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May 23, 2013
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?):
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Dec 21, 2014
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#include <iostream>
#include <string>
#include <cstdlib>
#include <iomanip>
#include <stdio.h>
using namespace std;
[Code]...
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Jun 27, 2013
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class AbstractSocket {
public:
AbstractSocket();
AbstractSocket(const int file_descriptor, const struct addrinfo* local_address,
[Code].....
My problem and question is the following, on ServerSocket::accept method I have to do a "client_socket = new Socket(abstractSocket);", and in Socket::recv_all method I do something like "buffer = new unsigned char[bytes_to_receive];". These two situations are somewhat problematic to me, because I don't wish to make the caller of the methods responsible for deleting this memory.
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I thought of placing an "unsigned char* buffer" inside Socket class, and to delete the memory allocated in the destructor and on consecutive calls to recv_all, but i don't believe this is the solution, and it doesn't solves me the problem for the "accept" method.
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Jul 30, 2014
recently I developed a class header only in C++ to deal with byte arrays. Since I developed programs in other languages that had some libraries to dial with byte arrays, I developed one that the syntax is very similar to other languages.
Since I'm not very familiar with memory management, I was concerned about somethings I've read about (ex: memory fragmentation).
Here is a very simple example of my practice:
class ByteArray {
public:
ByteArray(size_t size) {
buffer = (int8_t*)malloc(size);
}
[Code].....
The class is intended to be used as part of comunication protocol in a webserver, byte arrays are created and destroyed a lot. Should I use pools? Is there a better practice? Am I doing everything wrong (laugh)?
For those who wants to see the entire class: [URL]
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May 19, 2014
I am working on an OOP assignment (text handler) which part of its description is:
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My problem is first to allocate a dynamic memory like char** without defining the number of array elements (Each text loaded should only occupy the space needed for the text to fit. )and then store each story from text file (comprise of a few lines of text) into that dynamically located memory(char **)to be able to do some operation on it later.
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Dec 2, 2013
Dynamic memory allocation in array in c programming. I am trying to make the user to choose the size of array they want to engage in the game.
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And i also need limit the board size only from 4 to 9. And how do i do that.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <conio.h>
#include <malloc.h>
#include <ctype.h>
#include <stdbool.h>
[Code] .....
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Mar 31, 2013
Say I have a class with a few member functions, and only two data members: an int* Table; and an int Size;, to store the number of elements in Table.
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