If I have a pointer variable indicating memory location in which we have stored what user entered and the pointer is of type volatile if the user gives the character 'a' twice , then this character will not be fetched twice from the memory but only when the character is changed???
This is the one meaning of the volatile? the other is that the value will be changed without the program itself change it?
I just started deal with pointers in C, and one stuff confusing me...
Here is simple code:
int main (){
int var1 = 10;
int var2 = 20;
long ms = 10000000;
printf("Address of var1 variable: %p
", &var1 );
[Code] ...
But - when I run pmap - I don't see this addresses there:
Code:
# pmap -x 16496
16496: ./address
Address Kbytes RSS Dirty Mode Mapping
0000000000400000 4 4 0 r-x-- address
0000000000600000 4 4 4 rw--- address
00007f79cf8b8000 1576 260 0 r-x-- libc-2.12.so
00007f79cfa42000 2048 0 0 ----- libc-2.12.so
00007f79cfc42000 16 16 16 r---- libc-2.12.so
I guess - it's is inside stack:
Code:
# cat /proc/16496/maps | grep stack
7fff0d7e5000-7fff0d7fa000 rw-p 00000000 00:00 0 [stack]
But - how I can obtain this variables addreses, to see them with `pmap`? If I put them as "global":
Code: ...
#include <stdlib.h>
#include <sys/types.h>
int var1 = 10;
int var2 = 20;
int millisleep(unsigned ms);
int retpid(void);
[Code] ......
I have odd addresses in result:
Code:
Address of var1 variable: 0x600a94
Address of var2 variable: 0x600a98
I have got this error: I get the error: Identifier 'deposit' cannot have a type qualifier
I have defined this class
class BankAccount {
private:
double balance;
double interest;
int custNr;
[Code] ....
When I compile the program I get the error: Identifier 'deposit' cannot have a type qualifier ....
I'm fairly new to C++ and have begun working with pointers. I wish to create am array called sigmaf_point that reads data from a text file. I have managed to get that working, but when it comes to using this pointer I come across some problems. The array is created as such:
Code:
double sigma [5];
double *sigmaf_point = sigma;
void read(double *&sigmaf_point)
string s;
ifstream Dfile;
std::stringstream out;
[Code] .....
I then create a coordinate system inside the main file, as the program I am writing is about modelling the movement of atoms, which requires you to know the coordinates:
Code:
int main();
double **coords_fluid = new double*[5000];
for (int i = 0; i < n_atoms_methane; i++) {
coords_fluid[i] = new double[4];
}
Now, the problem arises when I want to calculate a new variable as so:
Code:
for (int i = 0; i <= n_atoms-1; i++) {
sf1=sigmaf_point(coords_fluid[i][3]);
}
I get the error C2064: term does not evaluate to a function taking 1 arguments, and a red line under sigmaf_point that says it must be pointer to function type. I am a bit confused about this.
In the code below. I believe I am returning the memory location of the value I am looking for. How can get the value?
main.cpp
int choice = 0;
PlayerMenu *newPM = new PlayerMenu;
File *file = new File;
// Menu for loading, creating or exiting the game
choice = newPM->menuChoices();
PlayerMenu.cpp
[Code] ....
I am not sure how to deference the value so I can get at the value instead of the memory location.
Under Microsoft, I use GlobalAlloc and GlobalFree to dynamically allocate and free memory. Intermittently GlobalFree is reporting error 998 (GetLastError() - Invalid access to memory location). I've checked my logs of addresses returned by GlobalAlloc against those being freed by GlobalFree and when the problem occurs the address causing the error has been allocated by GlobalAlloc and has not been freed before since allocation.
I can't reproduce it. Currently I'm checking for error 998 from GlobalFree and ignoring it if it occurs - which is not satisfactory. I have one function (AllocMem) that calls GlobalAlloc and checks for errors and another function (FreeMem) which calls GlobalFree and checks for errors.
My program uses AllocMem and FreeMem everywhere memory is required or freed. AllocMem and FreeMem are in a DLL. The program is heavily threaded and a different thread may call AllocMem to the one that calls FreeMem. I don't believe I've got a race condition etc as all the code in the program containing the AllocMem and FreeMem calls are part of a CriticalSection using the same variable.
What is a possible cause of this error?
How to change an enum type variable to a string type variable?
View 2 Replies View RelatedI have a contiguous sequence of section headers in a file (all the data in the file is stored in void * data), where each section header is the same size and has the same fields in the same order. So it's laid out like an array.
I have to:
- Use an offset value and the number of section headers variables to identify the location and length of the section header table (these are hdr.offset and hdr.length respectively).
- The offset value shows the distance between the start of the file and the start of the first section header (so I need a pointer to the start of the first section header)
- Apply a typecast to location of the section header table to process it as an array of section headers.
Here is what I have done, but I am getting a segmentation fault. What am I doing wrong? How do I fix this?
typedef struct {
unsigned int name;
unsigned int type;
} SectionHeader;
[Code] ....
I would like to convert a float or double variable into unsigned char variable and back.
float number_float = 23.453f;
unsigned char* number_char = (unsigned char*)malloc(sizeof(float));
number_char = reinterpret_cast<unsigned char*> (&number_float);
float* number_float_0 = reinterpret_cast<float*>(&number_char);
I am not getting the same value back.. why?
/*using GENERIC_COMMAND* A; as volatile generates error. but here i have to use union object as volatile i.e. volatile GENERIC_COMMAND* A; */
#include <iostream>
using namespace std;
typedef unsigned int uint32_t;
typedef unsigned long long uint64_t;
union GENERIC_COMMAND {
[Code] .....
I'm making a system like twitter for class called ShoutOut.com I want to be able to get the PublicShoutOut pointer pointed to by the start iterator and assign it to firstShoutOutToDisplay and secondShoutOutToDisplay because I need that in order to pass the pointers to one of my functions. When I step through the debugger the values in start are all default values like "" and so are the values in this->firstShoutOutToDisplay but the message that start points to is being output just fine.
EDIT: got rid of irrelevant code. Am I using the correct syntax to do this?
if (start != finish) {
//getting these because a shoutout needs to be passed to the function that displays
//options for a shoutout
this->firstShoutoutToDisplay = (*start);
[Code] ....
Why is it that in the STL it is standard to indicate a sequence of elements in a container by a begin iterator that points to the first element and an end iterator that points to one past the last element?
View 2 Replies View RelatedI'm writing a program that communicates with another program over TCP/IP. I need to assemble contiguous buffers of mixed data to send to the server. For example, one of the messages must contain multiple 32-bit integers and 64-bit floats, each in its own appropriate field. I also need to receive and decode similar buffers.
The Windows TCP function "send(socket s,char *buf, int len, flags)" takes a pointer to a character array to send. Likewise, the TCP function "recv(socket s,char *buf,int len,flags)" takes a pointer to a character array to fill. I've tried creating structures describing the send and receive messages, with the fields appropriately laid out. But the CODE::BLOCKS compiler complains when I try to hand send and recv the pointers to the structure variables. Am I on the right track, or is there a better way to do this?
We have to write a function named fibonacci that takes an int indicating the length of the series and then store it in an array of size 20 printing the sequence from largest to smallest. Here is the small bit i have so far:
#include <iostream>
#include <iomanip>
using namespace std;
void Fibonacci( int );
int main( ) {
[Code] ....
I just need something to get me on the right track.
I'm searching a program that can detect a special type of memory leaks, like these:
int a = 12;
char c[10];
char cc = c[a];
I am having a problem with a small exercise program. The program works the first time through the loop but not the second. It faults on this line:
cin >> *(pint + i1);, with this error: pint <Unable to read memory>.
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
int MAX(5);
int count(4);
int value(MAX);
[Code] ....
I 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* .
I am trying to make a function that allows me to allocate memory to a "mem" variable and setting each of its chunk's status to FREE. FREE is defined as 0. Below is my code of the function.
Code:
int allocate(mem *mm, int num_chunks, int chunk_size) {
int i;
mem *temp;
if((mm = (mem *) malloc((num_chunks + 1) * chunk_size)) == NULL){
perror("Failed to Malloc
[code]...
mem; If my function works the way it should, it should print out five 0 because that is how I set them in the function, but this is not the case. I've looked at my function for 2 hours, but I could not figure out any logical error. Now, I think my problem lies with my limited knowledge of pointer arithmetic. On the other hand, when I insert 1000 as the second argument into my function, it gives seg faults, which is not the case for smaller values like 5, 10, 15, etc.
So, I've made programs like Prime number searchers and such. But the problem is if I use an int or long int variable for the program I am limited by the variable size. I can't search through numbers larger than their memory size. So my question is: Is there a way to allocate memory to a single variable, NOT AN ARRAY, so I can make a variable as many bytes as I want?
View 3 Replies View RelatedWhat I'm trying to do is:
int *p;
someType memoryLocation;
cout<<"Enter your memory location: ";
cin >> memoryLocation;
p = memoryLocation;
cout << *p;
I was just messing around with some code, and was curious to if this was possible.
I'm working with memory mapped files and I have a block of memory that I've mapped to.
I want to write a function that returns a pointer to a portion of the mapped memory at an offset and length so I can write to it. I've never worked with memory at this level, is what I'm attempting possible?
I know that mapping functions can map to a part of the file at length and offset but I'm not sure if I should make multiple calls to map the memory from the file or just map the memory once and work with the portions I'm interested in using my proposed GetMemory function.
Code:
LPVOID m_lpData;
LPVOID GetMemory(DWORD pos, DWORD length) {
BYTE* buffer = (BYTE*)m_lpData;
buffer += pos;
// how to get a length of the memory?
return ((LPVOID)buffer);
}
How to draw a hollow triangle given a user input indicating the number of rows.
Eg:
Number of rows = 4
___*
__*_*
_*___*
*******
My idea was to split up the triangle into three parts (first row, middle part, last row) and I've managed to write some code on printing the first and last row of the triangle
Code:
int main() {
//Declaring the variables.
int rows, position;
//Prompts user to enter number of rows.
printf("Enter the number of rows in the triangle: ");
scanf("%d", &rows);
[Code] .....
What to do so that I can print the middle part of the triangle. All I know is that I need to use loops. I've also been told that drawing a flow chart would work but I really don't know how to even begin with a flow chart then transform it into code.
How do you store a variable in memory so that it isn't changed when the program closes? I don't have any experience with this and am just wondering how it is possible. I am creating a program and want it to store your preferences and scores. In a simple program, everything is just reset and I don't want this for my program. How do I store a variable so that it stays the same, but can be changed even when the program is turned off?
View 2 Replies View RelatedI'm attempting to pass a couple of variables over to my Item.cpp class, that is description and item_price. However under item.set(description,item_price), i get three errors. One under the . (period) saying : expected an identifier and two more under description and item_price stating that variable " xxx " is not a type name.
Main.cpp
#include <iostream>
#include "item.h"
using namespace std;
using namespace items;
int main(){
int n;
[Code] .....
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?
I 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 &.