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?
View 2 RepliesHaving 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 compiles o.k.:
Code:
int main(void){
char *a;
a = (char*) malloc (100*sizeof(char));
[Code]....
I get an error saying "pointer being freed was not allocated". This happens for free(a), free(*a), free(&a), free(&*a).
So if I no longer need "1234567"... how do I get rid of this memory element?
There is a part in the lesson that explains how malloc is used to allocate free memory to a pointer and gives us 2 examples:
Code:
float *ptr = malloc( sizeof(*ptr) ); and Code: float *ptr;
ptr = malloc( sizeof(*ptr) );
From my logic in the first case we allocate the memory to *ptr and in the second to ptr.
It's a bit confusing, am I missing something?
Consider this program:
Code:
// sb_string class v1.04
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct sb_string {
[Code] ....
And here is the output I got:
Code:
[harshvardhan@hari-rudra] ~/Desktop% gcc49 -o test test.c
[harshvardhan@hari-rudra] ~/Desktop% ./test
-before Value of len = 1
(in_function)-before Value of len = 1
(in_function)-after Value of len = 1
-after Value of len = 1 I was trying to make a little easier to work with string. Once the memory is allocated by malloc via sb_init() function, the sb_massacre function wasn't working to deallocate the memory. I had used multiple versions of gcc and clang but the result is same.
How to free the memory and address,value
Server:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
[Code] .....
Client:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
[Code] .....
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.
An attempt to create a class which is basically a mimic of vector<int> i don't seem to know how to delete pointer x in a destructor to free memory, also on pushback and pushfront methods, i can't free y when i implement delete[] y; y=NULL; i get some NULL out put when cout 'ing the object in main, why is that happening and how do i free memory y.
#include<iostream>
using namespace std;
class vectorOfint{
int* x;
int size;
public:
vectorOfint();
[Code] .....
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.
View 5 Replies View RelatedSuppose if i code like this,
while( true ) {
int x;
// do some thing;
// break on some condition match;
}
whether memory is allocated for ints x one time or each time it hits int x.
For static variables when the memory will be allocated? During compilation or linking or loading time? In below program i am getting error :
(Error C2099: initializer is not a constant in microsoft visual studio) .
If i initialize x = 10 or any constant it works , why?
Code:
main() {
int i=10;
static int x = i;//error ?
if(x==i)
printf("Equal");
[Code] .....
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?
How can I view the number of bytes that have been allocated by using the malloc function?I tried:
mem = (float*)malloc(num*sizeof(float));
printf("The amount of memory allocated using malloc is %d.", mem);
Note: The variable "num" in my program is equal to 7.But every time I run the program, this value changes.
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]?
View 6 Replies View RelatedI 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:
34932 13854 13854 2012-01-07
172098 49418 53269 2012-01-07
I have written the following code:
Code:
#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.
I am trying to simulate memory in C. I want to create a structure in C that will hold a 8bit opcode and a 32bit memory address. This would simulate a 40 bit instruction for my simulator.
I read in an old book that packed structs could be used for this to not waste space. What are the draw backs for using this? I am not worried about wasting space, but just looking for a simple way to access the memory instructions. Below is a sample of the structure that I want to use.
struct memory_area {
unsigned int opcode:8;
unsigned int address:32;
};
I have one requirement to store an array of structure at shared memory. Also the shared memory should have one counter to store number of elements in the array.
I tried to look at some placed but didn't find anything relevant.
So my first question, is it possible that we can store two things on same shared memory. And second if not then how to achieve the same?
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 have an assignment that wants me to better understand how certain calls like malloc() and free() work. I'm supposed to have one function that allocates a pool of memory for the program to use (this is the only place where I'm allowed to use the malloc function. Anyplace else is off limits, except when allocating space for data structures.) Another function needs to be defined that allocates memory from this large pool of memory that we have already allocated. A third function needs to free a block of memory when a call from function main is made and a fourth does something else (haven't gotten that far yet.) I'm not sure if it's ok or not, but I'll attach the pdf form that describes all the requirements. If that's not ok, I'll delete it.)
Anyways, when thinking of data structures to use for this particular problem, one doesn't jump out at me as being THE data structure that would be most useful. How I would imagine using it is to store the addresses currently being used as well as the block length of those addresses (so basically, each node of the linkedlist would have a pointer that points to an allocated address and another field that told the size of the allocated block of memory.) How to communicate to the large pool of memory that a certain block of memory has been allocated and shouldn't be used until a free is made on that specific block of memory.
Attached File(s)
pa3.pdf (61.07K)
I am trying to run a programme implementing a function with structures in c... which is:
#include<stdio.h>
#include<conio.h>
struct store {
char name[20];
float price;
int quantity;
[Code] .....
Code:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
/* h(a)=abcab,h(b)=acabcb,h(c)=acbcacb */
void h_i(int i, char *w, char *a, char *b, char *c)
[Code] .....
Above program increases string like this example.
Let say h(0)=01 and h(1)=10 and let say our first string is w=0 h(w)=01, h^2(w)=0110 h^3(w)=01101001..etc.
We have used h map, which is given in the program comment statement. Same thing, program is doing for three letters. These three letters we have passed as argument in h_i function. e.g. h_i(2,w,"a","d","g") function will apply the 3 letter map h(definition is given in commented form in program) 2 times on string w.
In program w=a; and three letters are a, d and g. /* h(a)=abcab,h(b)=acabcb,h(c)=acbcacb */ here b=d and c=g.
Above program gives core dump at free(w2) free(w1). if we remove these free statements then it gives correct answer. But, we want to free w1 and w2 in the above code. How can we make free both w1 and w2 strings?
how is the best way to free unsigned pointer array allocated with cmallc?
Code:
uint8_t *buf;
buf = cs_calloc(ca->len + 13);
i do like this , but i know this is not quite right , since i got compile warning passing argument 1 of ‘free’ makes pointer from integer without a cast
Code:
for (i = 0; i < ca->len + 13; i++)
{
free(buf[i]);
buf[i] = NULL;
}
free(buf); do i need to free each element of array like above?
I don't use Visual Studio and/or C++ so I would like to do it without them. I found this article c++ - How to determine CPU and memory consumption from inside a process? - Stack Overflow
I tried some lines of code but no one works for me.
Code:
#include "windows.h"
typedef struct _MEMORYSTATUSEX {
DWORD dwLength;
[Code]....
These was just my first tries to work with da MEMORYSTATUSEX.
I would like to find out if there is free memory at least ... (some value) and similar.
I'm currently trying to write a program that takes an integer input from the user and displays that number of square-free numbers. I've gotten most of the program to work, but I encounter an error during the noSquare function that causes it to print incorrectly.
A square-free number is a number that is not evenly divisible by the square of any prime number. It's hard to see the bold in the code area, but it begins after the "//I think below is where the problem is"
#include <iostream>
#include <vector>
using namespace std;
[Code]........