C/C++ :: Multiple Malloc Calls On One Variable?
Feb 13, 2013
I'd like to know what happens if I use multiple calls to malloc() on one pointer (without free) in a single function. Here is the example:
void *data_thread(void *sockfd_ptr) {
int sockfd = *(int *) sockfd_ptr;
const int BUFSIZE = 5;
char recvmessage[BUFSIZE];
char *headerstr = NULL;
char *newheaderstr = NULL;
[code]....
what happens with newheaderstr every time malloc() is called. There isn't a realloc() or anything. I didn't think it looked right to keep using malloc() like that.
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Oct 9, 2014
My function "MatrixMul" returns an int array with multiple values Let's say, res[0] and res[1]
When I'm calling the array in a for loop for multiple times, and when I'm storing the results in another array, in each iteration the results are over-written with the new results.
If the first call returns [0,1] the array will store [0,1] at index [0] and [1], which is fine, but when I'm calling the function again, the new results are stored at the same indexes [0] and [1] How can I avoid that?
The code is:
class Hill_Cipher
{
string AtoZ="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
public string Hill_Cipher_Enc(string input, int[,] key)
[Code].....
For example, my outPut contains the following: "TH","IS","AT" when I'm calling the function with the first element of array "TH", it converts "T" to its equivalent number and apply some calculations and same with "H". Let's say the final answer is 20 for "T" and 30 for "H". The problem is that every time, encChars will store the values at index 0 and 1: encChars[0]=20 encChars[1]=30 When I call the function again it will store the new values at 0 and 1.... That's because I'm not changing the index value for encChars on each call, so how do I do that?
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Mar 31, 2014
Code:
scanf("%d", &a);
printf("A");
scanf("%d", &b);
prints "A" after calling scanf two times instead of between the calls (first scan, then print, then scan). I'm using GCC v4.6
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Apr 17, 2014
My application calls malloc in multiple subroutines, finally releasing all using free. This is done using my zalloc library (see my other post: [URL] .....
Somehow, when the applications tries to detect the available ammount of memory at the end of the test (allocating, freeing, testing), the freemem function gives me about 4-6MB less memory than at the start of the test? (out of 21MB available on the device at the start).
All memory is allocated and freed using the malloc/free routines within the library, with the exception of the SDL functions, which are registered externally on allocation and release.
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Sep 7, 2013
I was trying out programs based on extern and as i understand, this is useful when accessing variables across multiple files having only one definition. But i tried a simple program as below without "extern" and thing seem to work when i expected it would fail during linking process
Code:
file5.c
1 #include <stdio.h>
2 #include "var.h"
3
4 int main() {
5
6 printf("
File5.c a = %d", a);
[Code] .....
As i have included "var.h" in all header files without extern, "int a" would be included in both the .c file and during linking, compiler should have thrown a warning or error message but it compiles file without any issue. Shouldn't var.h have the following "extern int a"?
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Mar 9, 2013
In the existing code,fork has call parallel to create process.my job is to store all the process id into vector so that we can verify the status of the jobs. I was able to save all the jobs but as the callback happen so I have lost my all value which was store into vector.
How can i maintain variable between multiple process.
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Oct 29, 2014
I tried to create a multiple choice list and I want to assign the value of the answer option chosen by the user so I can use it later on in the code. Later on in the code i've asked how many people (p) want a drink and multiplied it by the chosen size to calculate the price c = p * n where c is cost, n is price and p is number o of people At the bottom i tried to assign parameters where depending on what option the user has chosen n will be assigned to the chosen value...
{
printf("SELECT TYPE OF PAINT:"); /*multiple choice of paint */
printf("1. Large ");
[Code]....
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Dec 24, 2013
I have a quick question about passing multiple variable to a func that has (stringstream & text). Here is the code:
void PrintText(stringstream & txt) {
cout << txt.str() << endl;
}
void main() {
[Code] ....
How to make second one work?
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Jan 6, 2015
I have a multi-thred piece of code that should be fast. As I have to update a Database from time to time, I wonder if I do it in a prpoer manner with calls like this:
Task.Factory.StartNew(()=>update_execution_to_db(exec));
Those are my sporadic updates, my ongoing update have a queue and a dispatcher thread reading from the Q, I just don't want to use this overhead for the sporadic updates.
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Mar 7, 2012
Code:
class A {
virtual method1() { };
};
class B : public A {
method1() { }
}
Code:
A* a = new A();
a->method1(); // call B's method1?
Is it possible to call B's method1 in this case?
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Apr 27, 2013
This is simple recursive solution of Fibonacci number:
Code:
int fibo(int n)
{
if(n<=1)
return 1;
else
return fibo(n-1)+fibo(n-2);
}
Now the recursion will generate a large recursion tree, like if n=5, 5 will call (5-1), (5-2) or 4,3 . What I want to know is, will fibo(n-1) will be called 1st go all the way to the base case 1, then do the summation or fibo(n-2) will be called right after fibo(n-1) ?
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Apr 18, 2014
Let's start with something from the c++ reference:
... delete[] is an operator with a very specific behavior: An expression with the delete[] operator, first calls the appropriate destructors for each element in the array (if these are of a class type) ...
I was wondering if I can tell delete[] to not call destructors, for example if I already know that the delete[] statement should be delete without []. That would be very useful for memory management/memory leak detection.
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Aug 28, 2013
The below code is taken from open source filezilla project
(FileZilla_3.7.3_srcfilezilla-3.7.3srcinterfacebookmarks_dialog.cpp)
Code:
#include <filezilla.h>
#include "bookmarks_dialog.h"
#include "sitemanager.h"
#include "ipcmutex.h"
#include "themeprovider.h"
#include "xmlfunctions.h"
BEGIN_EVENT_TABLE(CNewBookmarkDialog, wxDialogEx)
EVT_BUTTON(XRCID("wxID_OK"), CNewBookmarkDialog::OnOK)
EVT_BUTTON(XRCID("ID_BROWSE"), CNewBookmarkDialog::OnBrowse)
END_EVENT_TABLE()
I'm unable to understand what are these lines after the #include. They don't end in semicolons. Looks very much like function calls.
Are BEGIN_EVENT_TABLE, EVT_BUTTON and END_EVENT_TABLE function calls? Function calls should end with semicolons right?
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Mar 29, 2012
I created a server application but i need to know how to delete my calls to new
Code:
CBaseServer::CBaseServer() {
}
CBaseServer::~CBaseServer() {
}
void CBaseServer::Start() {
struct sockaddr_in ain;
[Code] .....
Also when I call this..
Code:
new CThreadManager();
It gives me this warning...
warning C4345: behavior change: an object of POD type constructed with an initializer of the form () will be default-initialized
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Apr 24, 2014
I have several functions doing similar things, inside their implementations, the parameters are the same, but they call different methods.
I want to create one function to make the structure easier, and reduce the duplication. I heard template might be one solution. But I am not sure how to use it in this case.
void GetA(...XXX) {
for()
{
[Code].....
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Mar 15, 2015
I'm trying to implement a code that recursively calls itself and prints the given digits in ascending order, i.e. if the number is 5, then the function will print 1 2 3 4 5. I cannot use loops in any way!
The problem I have is with keeping my variable i at a set value each time the function calls itself.
void print_ascending(int n){
int i = 1;
if(i < n) {
printf("%d", i);
i++;
print_ascending(n);
}
}
Of course, the problem with this code is it will re-initialize the variable i to 1 every single time and infinitely loop to print 1.
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Apr 19, 2013
I need to be able to disable the items on a CCheckListBox but I can't change the code that calls AddString. I know I can use the CCheckListBox::Enable function to disable an item if I have an index but I don't have the index which would be provided by AddString.
I've tried intercepting the LB_ADDSTRING message and then looping through the items in the control but the string has not been added at this point so the last item in the list is never disabled.
I used Spy++ to see what messages were being sent and I noticed that LB_GETTEXT was sent so I tried intercepting this message (ugly hack) but this caused my app to hang - I assume because of the number of times the message is sent. Is there a way to disable the items?
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Aug 19, 2013
I am trying to write a menu program that will be broken down into a series of calls to function for each of the menu items. Two of the menu items will be simple programs which I wrote.
I want two of the functions to run one of the two programs I am trying to include as items in the menu.
So far I am only familiar with variables, loops, if statements, and I just learned how to write functions.
The problem I am have is that I don't quite understand how to write a function that will run one of the two programs. Also I am having a hard time writing the program in away that would allow the user to select the menu items.
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Nov 2, 2013
I wrote a program to detect if a graph is tree or not. Initially it was using static memory. Later I changed it to use memory dynamically using malloc().My problem is that, my program it works great for case when graph is not tree but fails if it is.
Code:
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
int main()
}
[code]....
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Mar 3, 2015
This is my code without malloc. I need to change the array size so there is no max size for each matrix. I must dynamically allocate space for all arrays used. So I need to use malloc to create my arrays. So I cant use int A[rows][cols].
Code:
/* This program asks the user for 2 matrices called A and B, as integers, and displays their sum, C. The max dimension of each matrix is 100. */
#include<stdio.h>
// Construct function
void construct()
{
int m, n, i, j;// Variables
int first[100][100], second[100][100], sum[100][100];// Matrices variables
[Code]...
Im having a hard time understanding/using malloc. Should first, second, and sum be single pointers or double? How do I scan the matrix correctly? And how do I add them properly? Do I have to change my for loops?
Code:
/* This program asks the user for 2 matrices called A and B, as integers, and displays their sum, C. The max dimension of each matrix is 100. */
#include <stdio.h>
#include <stdlib.h>
// Construct function
void construct()
[Code]...
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Jan 6, 2014
I am confused whether 'malloc'ing an array of pointers and pointer to a group of arrays are the same.
Suppose I need an integer pointer to a group of arrays of 2 elements each.
int (*LR)[2];
So to dynamically allocate this pointer for M number of arrays suppose, then what is the correct syntax?
int M;
scanf("%d",&M);
int (*LR)[2];
LR = (int*)malloc(2*sizeof(int));
Whether this is correct??
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Oct 27, 2013
I am curious as to what is happening to my pointers and everything once I call malloc to create space for 5 integers to try to make a stack.
Code:
#include <stdio.h>
#include <stdlib.h>
void add(int * TOP, int * stack);
int main() {
int *stack = NULL;
int *TOP = NULL;
stack = (int *)malloc (5 * sizeof(int));
[Code] ....
I am guessing that when I initialize stack to malloc, stack now stores the starting address of where the space is taken out, and also assigns TOP that address too. I get the choice from the user (b) to get the instruction to try to push on the stack. I was told that the if statement in the function checks if the stack has passed the bounds of 5 elements. If not, it assigns the scanned variable and puts it into what TOP is pointing to and increments TOP to the next address. It is not working and am wanting to see where my logic is wrong.
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Oct 17, 2014
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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Jan 27, 2013
i want to improve my knowledge about the dyn allocation of char pointers... with this code i wanted to type a string and insert the string in a array created dynamically:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char c;
char *test=NULL;
unsigned int len;
}
[code]....
why there are these 3 initial character '' ')' ':' that i didn't have typed...
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Dec 15, 2013
i want to ask how does malloc works on an array for instance can i dao this
Code: p=100;
int array[10];
array = malloc(p * sizeof(int));
then will the size of int be 100 so will i be able to do like
Code:
array[11] = 12 ; ???
also if i have a 2d array how can i use malloc on it and how does this works with pointers????
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Jul 16, 2013
Notes: Im Using SDL, Im using Codeblocks to code
Ive narrowed down my crashing problem ( using printf's ) to a malloc call I had to use printf's because when i ran the program in Codeblocks debugging mode, it did not crash and ran fine, but when i ran it normally, it would crash, giving me this error:
fatal signal segmentation fault (sdl parachute deployed)
Inside my code, I created a malloce function that checks malloc for me ( so i dont have to do it )
( general.h )
void* malloce ( size_t size )
{
printf ( "start malloce %i
", size );
[Code]....
funny thing is that i called this malloce function about 20 times before it hits this part of the code, it is unknown behavior to me!
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