I have a question about memory allocation.I have a function that calls a lot of object constructors, which in return these constructors will allocate a lot of memory.Now, in my program I am sure that if I first call this function , say it will call the constructor of 100 object.If I call this function again and again, I am sure that it will only call the constructor 100 times again, and thus I am sure that the memory allocated in the first call can be reused again.
How can I reuse the memory allocated in the first call?Can I use something like boost:object_pool so that I can tell the pool to restart from the begining and do not allocate extra memory, just use what you already have?
We have a proprietary third-party library that we make calls into via an API. Through a series of API calls, this library manipulates specific sets of data. Prior to making these calls, there are some API calls that are necessary in order to initialize the library in preparation for a specific set of data. One of the calls tells the library to allocate some memory and then perform whatever initialization is required. This particular API call returns a pointer to char (char*) that is later used as an argument for a few other API calls. My question is... Is there a way, or maybe some kind of trick, to tell exactly how much memory was allocated? It doesn't matter whether or not the solution (if there is one) is C++ related, or some series of OS commands. FYI: We're running on Redhat Linux 6.2 and using GNU C++ 4.4.6.
I'm trying to free allocated memory for structure. It seems like free() gets only pointer and not regular types . my question is basic and simple – is passing pointer to free() frees the pointer or the variable it points at? or both?
I have a pretty big std::vector<matrix>, where matrix is a custom class defined by me. I would like to know how much memory has been allocated to that vector at a certain point in time. Is there any way of doing this in c++?
Or is my only shot, taking a look at the task monitor of windows/unix/whatever at execution time to estimate this?
When declaring char array[10], memory is allocated for 10 1-bit memory locations. Is extra memory allocated for storing the address of array[0]? In expressions, is array equivalent to a pointer constant or is it an identifier for a memory cell containing the address of array[0]? In other words, is array a variable or an alias for &array[0]?
I am having issues freeing memory that I allocated when adding a node to a doubly linked list. I have tried adding free() at the end of the remove function from the list with no luck. I have tried using all sorts of temporary nodes and dummy nodes to free without losing node information. Have tried storing current node, moving to next one, then freeing the old current one, without luck. Everytime I try to free a node it destroys the list. It loses important node information and can no longer operate properly and I am met with all sorts of memory crashes. I will post my add and delete nodes functions here:
/** * Adds a node to a given list * * @param q pointer a a list * @param node pointer to the node to be added */ void list_add(list *q, path *node){ path *pn; if(!(pn = (path*)malloc(sizeof(*pn)))){ perror("malloc"); exit(1);
[Code] ....
Those free's at the end are to get rid of nodes I malloced in find_path. This find_path works really well when run once lol. It finds shortest path and prints it no problem, but doing it over and over again will be problematic as it is leaking almost every bit of memory it uses />.
So in short, how to free an allocated node when I remove it from a list while still being able to use it? I have tried moving the remove function to different locations like the end of the file and still no luck. I even tried allocating a new current_node each iteration of while loop, using it, then freeing it at the end of the while loop and took out the allocation in the list_add() function. This didn't work either />. How to stop the leakage.
I am trying to store each value of a column from a text file into an dynamically allocated array, which needs to be globally declared for further usage in the program.The input textfile contains the following:
#include<stdio.h> #include<stdlib.h> #include<string.h> int main() }
[code]....
The commented printf line gives the entire values of the column, which proves that the file is correctly being read.But on compiling this program I get both compiler warnings and finally segmentation fault.
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.
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.
I am currently taking a C# class. Our current assignment has us entering a player name, and number of hits and displaying these in one set of labels. I have coded everything for the primary function of this program and it works. However, I also have to have a second set of labels that show the highest number of hits entered (if I enter 44, the first and second labels change to 44; if I then enter 27, the first label changes to 27 and the second stays at 44; and if i enter 55, the first label changes to 55 and the second label changes to 55) and the corresponding player name. I have tried searching and reading and I can't seem to figure out how this is done.
On line 128 I'm attempting to delete an image file that was previously shown in an ItemsControl, but was removed by line 126. So the image is not being shown in the program at the time I'm wanting to delete the file.
Error:Additional information: The process cannot access the file 'c:StudioExit PopupKeith Sketch.png' because it is being used by another process.
My Code:
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows; using System.Windows.Controls; using System.Windows.Data;
I have a small questions in the behavior of Structure, I have declare a structure with 10 components. Some of the components in the structure has already their value but when I use
The structure components in a function DLL function those value I set previously has been deleted or empty. I don't know what is the problem...
I'm using web cam to save,update the image in base directory folder.I can save the image but, while attempting to update the image..I caught an error!!
C#.Net: The process cannot access the file 'C:..~..inDebugcustomer_photos10.jpg' because it is being used by another process.
Unoptimized problem: I work on a table (vector of vectors). vector< vector<double> >
Optimization: If the current set of vectors is v1...vn (so each vk is a vector of double), my problem is such that I will only work on the last M of the vectors, the earlier vectors are irrelevant. I would like to reuse space to make the algorithm scalable, so I want to delete the vectors that can be forgotten. I read in a new vector, I delete the oldest vector.
Im tasked with reading a data file, this is an example snippet
list of trophy winners year facup leaguecup 1stdiv 2ndiv 1960/61 Tottenham Hotspur Aston Villa Tottenham Hotspur Ipswich Town 1961/62 Tottenham Hotspur Norwich City Ipswich Town Liverpool 1962/63 Manchester Utd Birmingham City Everton Stoke City
The file starts in 1892 and is up to 2011/12, there is data missing for some years due to the wars etc,
once ive read the file, i need to store the data, for me to re-use.
There are a lot of useful link regarding reading data in, but they tend to be with very small files with say 10 lines of numbers.
I've got some code in C++ that does some basic analysis on price data and I run it from the cmd prompt. One of the functions I had built to read in the data is as follows:
How would one merge this type of code into a Qt GUI? Ideally, I'd like to use something like QFileDialog to open up a folder with my data files, select a file, and then read the file that the user selects. Would the main.cpp look something like this?
int main (int argc, char *argv []) { QApplication prog (argc, argv); QPushButton *load_button = new QPushbutton ("Load File"); QObject:: connect (load_button, SIGNAL (clicked()), &prog, SLOT ( (ReadPricesfromFile function?); load_button-> show (); return prog.exec ();}
is it better to reuse an existing variable or create a new variable for the following situation:
/* Is this faster: */ glm::mat4 newViewModelMatrix = (*existingViewMatrix) * (*existingModelMatrix); /* Or is this faster? */ glm::mat4 existingViewModelMatrix; /* declared in class header - initial value assigned in class constructor */ existingViewModelMatrix = (*existingViewMatrix) * (*existingModelMatrix);
I have the following dynamically allocated 2D array:
Code:
int num_rows = 100; int num_cols = 3; double **myArray= (double**)malloc( sizeof(double *) * num_rows); for(i = 0; i < num_rows; i++) { myArray[i] = (double*)malloc( sizeof(double) * num_cols); }
After sorting the array based on the values in column 1,:
Code:
qsort(myArray, num_rows, sizeof(myArray[0]), comp_function); int comp_function(const void* a, const void* b) { double **p1 = (double**)a; double **p2 = (double**)b; double *arr1 = *p1; double *arr2 = *p2;
return arr1[0] - arr2[0]; }
I need to split the array into two halves so that I can pass each separately into another function that accepts a type double ** pointer. What is the most efficient way of splitting the array? Is it possible to keep the original double ** pointer for the first half of the array and then assign a new double ** pointer to the second half of the array?
When I first learned about dynamically allocated arrays in school, I always thought we used them for passing arrays as parameters to functions. But the more I have been practicing coding, I see now that normal arrays can be passed as parameters to functions. So, what is the advantage? Why do we even need them?
I am trying to delete these arrays NumArray1.array and NumArray2.array at the end of my program so that there is not a memory leak. However I always get a double free or corruption error in runtime error with delete[] array_name. I have tried many times to use nullptr, but no matter what my compiler does not recognize it as being declared in the scope of my delete function. (I have commented out the that function for now.)
What is also strange about this is that I can perfectly use delete[] a1.array, which corresponds to NumArray1.array, but any of the other times I have tried to use the command, it has always resulted in syntax or runtime errors. Online resources do not adequately explain this scenario, though I am sure it exists elsewhere. all of my attempted solutions have failed, and I am completely at a loss. how to free the dynamically allocated arrays at the end of my program?
#include <iostream> #include <assert.h> using namespace std; // Define a struct type, each struct type variable has three // member variables: array, capacity, and length. Togther these // three variable represent a partially filled array.
I have an abstract class Base, with derived classes Derived1, Derived2, etc. I don't know how many there are. So, I have declared an object of Derived like so:
Base* der1 = new Derived1(/* constructor details */);
That gets passed to a function, which modified the data contained by this pointer. However, I need to keep the data from the object, which means that I need to copy the data somehow. The problem is, this copying needs to be done within the function, due to the requirements of the program. I do not know what type the object is, This function will need to reset this data potentially hundreds of times, so I can't just provide lots of objects, as either the function will run out of objects to call or I will run out of space in memory.
How would I create a copy of this, so that I would be modifying a temporary object that could be deleted and I would keep the data that I started with?
I have changed my const global int NUMLABS to a non constant variable so that the user can decide how many labs to input. I adjusted the parameters of each function to add NUMLABS becuase the variable is no longer constant. But now main() returns 0 right after the user chooses how many stations to put in each lab. I am having difficulty understanding these dynamically allocated arrays.
This program uses dynamic arrays to store login information for four labs. Each of the four labs is referenced by the labs[] array which is indexed from 0-3. A pointer in the labs[] array then references a dynamic array that is of size for however many computers are in that lab.
Written by: Luca Del Signore Last modified on: October 3rd Known bugs: N/A *********************************************************************/ #include <iostream> #include <cstdlib> using namespace std;
I understand why you cant define them but why cant you name them. Or is it that you must always define them in order to name them?
Why do I have to always use a pointer???
Or is it that dynamically allocated variables on allocate space for a type to be stored and not really the variable itself so you must use a pointer???
