Should i never return a pointer to a local variable. i have seen the following code in the standard text book.
Code:
struct node *add_to_list(struct node *list, int n)
{
struct node *new_node;
new_node = malloc(sizeof(struct node));
// some code here
return new_node;
}
new_node is a local pointer then why is he returning the new_node? Is it wrong or am i failing to understand something?
I hear all the time about the rule of not returning a local pointer, but I'm not exactly sure what that insinuates. Would this example be classified as violating that rule?
class Foo {
public:
Bar* ReturnBar() {
Bar* temp = &bars.at(0);
return temp;
}
private:
vector<Bar> bars;
};
I know that this code is wrong because it returns the address of local variable which no longer exist after function:
int *f1()
{
int x = 2;
return &x;
}
However, why this one does not show problem and runs fine, here the pointer p is also a local variable:
int *f2()
{
int x = 2;
int *p;
p = &x;
return p;
}
I need to transform a local variable into a global variable so I can use it in one of my functions. I thought about passing the value as a parameter to this function but I can do this since the function is called inside the while loop and this variable counts how many times the while loop does (so the final value is outside the loop). Example to visualize better:
Code:
while(condition) {
function(parameter1, parameter2);
count = count + 1;
}
printf("%d
", count);
So, I need to transform the final value of "count" into a global variable. Can I do this?
#include<iostream>
#include<stdlib.h>
using namespace std;
int Name(),Minimum(),Maximum();
int main() {
int name=Name(),minimum= Minimum(),maximum= Maximum();
[Code] ...
There are error to let user to key in minimum and maximum values, i would like to know whats the problem?
Here is my overloaded operator :
const double & Waz::operator()(int i,int j) const {
return ((WazImpl const)(*p))(i,j);
}
Where in Waz class I have : WazImpl* p; and in the class WazImpl I have an operator () const
The warning is : Warning C4172 returning address of local variable or temporary
As far as I understand I'm returning a temp variable which is destroyed somewhere else what can I do to fix it?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Furniture {
class Program {
static void Main(string[] args)
[Code] ....
I tried changing the type of variable to char but i still get the same result. i also tried using a switch statement which was my first choice but i had the same issue.
I keep getting the "Uninitialized Local Variable" error. But for my code it's says it's the variable 'pay' in my Manager Function. This is the only error that is popping up.
I've tried setting pay to 0 but when I do, I get a bunch of external errors. I've also tried assigning pay to WeeklySalary like this:
double pay = WeeklySalary;
//Calculating pay for a company
#include <iostream>
#include <iomanip>
using namespace std;
//Function prototypes
double managerFunction();
double hourlyWorkerFunction();
double commissionWorkerFunction();
[Code] .....
{
//Declare Variables
decimal hrsWrkd, otPay, grossPay, taxRate=0, taxAmount, netPay,basePay, wage;
string maritalStatus;
const decimal WORKWEEK = 40;
const decimal OTRATE = 1.5m;
const double m = 0.15;
[Code] ....
The error message I am getting is Use of unassigned local variable 'otPay' . I see its been declared and been used in the code so the error is confusing, also when i run the program i noticed that it doesn't take out the taxes.
So I have been working my way through this assignment and I'm just stuck now. I cannot get this work properly It just tells me I'm trying to return a local variable when attempting to return postfix in the to_postfix function. It is line 97 that wont compile. Also I cannot change anything in runner.c.
Calculator.c
Code:
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <ctype.h>
4 #include <string.h>
5 #include "stack.h"
[Code] .....
I got the following lines of code from a book. The variable char c is being used here to demonstration local variable declaration.
while(char c = cin.get() != 'q') {
cout << c << " wasn't it" << endl;
if(char x = c == 'a' || c == 'b')
cout << "You typed a or b" << endl;
else
cout << "You typed " << x << endl;
}
It compiles and runs. There are two issues when I try to run it.
1) It seems to loop through two times for every entry. If I insert cin.ignore() just before the closing bracket, it seems to work better.
2) the variable c does not seem to have the character I entered when examined in the if statement.
What is happening with the variable c inside the while loop scope?
Does c actually get initialized?
#include <iostream.h>
#include <conio.h>
int main() {
int a;
cout<< "ingrese un numero entre 1 y 4 gracias
";
cin>> a;
switch(a)
[code].....
is it possible to have a global variable pointing to a different address depending on the thread?
Imagine one would like to use threads with the loop:
for (i=0;i<n;i++){
globalPointerVariable=getAddress(i);
DoThingsUsingThe_globalPointerVariable();
}
I am doing a piece of gui code on some embedded system.
I'm trying to find a way of eliminating the local variable kEvent:
Code:
EVENT kEvent;
....
Code:
kEvent = EVENT_UPSTREAM;
xStatus = xQueueSendToBack(getEventProcessorQueue(),&kEvent, 0 );
....
I tried this, it doesn't work:
Code:
xStatus = xQueueSendToBack(getEventProcessorQueue(),(EVENT *)EVENT_UPSTREAM, 0 );
Shouldn't this work?
Here is the code,
Code:
class A {
};
A& CreateObject() {
static A a;
return a;
} static A aa;
int main() {
return 0;
}
So is there any difference between a defined in CreateObject and aa?
i always get error case bypasses initialization of a local variable
here's my coding
my header files
Code: #include <stdio.h>
#include <conio.h>
#include <iostream.h>
#include <fstream.h>
[Code].....
i'm using borland c++ v5.02
When a declare a string e.g.
Code:
char str[30]; as a global variable, the srting is initialized to NULL.
But if I declare char str1[30] INSIDE main(), then the string has garbage inside.... Why this happens??
E.g. the following code snippet...
Code:
#include <stdio.h>
char str[50];
int main(){
char str1[50];
[Code] ....
i have highlighted the errors in block letters.
#include<fstream.h>
#include<conio.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
void login();
struct date {
int dd,mm,yy;
[code].....
Can local variable be passed as the parameter for a new created thread procedure? Here is the example code:
Code:
void CDLG::some_function()
{
CString strFileName="abc.doc";
//local variable, can it be valid for being passed into the following new thread???
//Can strFileName still be accessed from within the stack of thread procedure?
::AfxBeginThread(ProcessContentThread,(LPVOID)&strFileName);
}
[Code]...
There is another method using variable on the heap,
Code:
void CDLG::some_function()
{
CString strFileName="abc.doc";
CString* pstrFN=new CString(strFileName);
::AfxBeginThread(ProcessContentThread,(LPVOID)pstrFN);
}
[Code]...
I test these code, both methods work as expected, but I doubt whether the first method is a good way. OR if only the second method is the correct way to pass a parameter to a thread.
In Visual Studios I keep getting this error. cpp(36): error C4700: uninitialized local variable 'Eligible' used
Code:
#include <iostream>
#include <string>
#include <iomanip>
#include <fstream>
#include <cmath>
using namespace std;
void Getinput(int& Loantype, double& Income, double& Totaldebt, double& Loanamount);
[Code] ....
As the title says, i'm using a function which returns a pointer to a struct:
the struct is the following:
Code:
typedef struct POINT
{
uint16_t x;
uint16_t y;
}
Coordinate; the function i'm using:
Code:
Coordinate * Read_XTP2046(void)
{static Coordinate screen;
//calculations to determine the coordinates
screen.x=(temp[1]+temp[2])/2;
screen.y=(temp[0]+temp[2])/2;
// and so on...
return &screen;}
The question is: how do i catch this pointer and make it into a Coordinate struct in which i can read the x and y.
In my main program i would do the following:
Code:
Coordinate cor;
cor = Read_XTP2046();
This does not work, as the function returns a pointer, but how to transform this pointer into a Coordinate struct.
I am trying to return a char pointer so that i can re use it again. I am writing a vigenere function that takes a message, a key and an initialization vector where it performs the encryption, prints out the encrypted message and returns the encrypted message. I print out the process step by step and everything works, however i pass the answer and print it out again and only the first letter gets changed. I put my code below and my output right after that.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
void decrypt(char *to_encrypt, char *key, char* pct);
enum flag{encryption = 1, decryption = 0};
[code].....
I have a class which looks like the following:
Code:
class Gadgets {
public:
Data* GetData() const {
return _data.data();
}
const Data * GetDataConst() const {
return _data.data();
}
private:
QSharedPointer<Data> _data;
}
You may ask why i have the second GetData() method that return a pointer to my private member, which will then expose my private member externally. I provide this function just for the case where user can do the following
Code:
Gadgets * myGadgets = new Gadgets();
myGadgets->GetData()->ModifyData(.....);
My question pertains to the use of QSharedPointer of data(), where in the doc, it says
T * QSharedPointer::data () const
Returns the value of the pointer referenced by this object.
Note: do not delete the pointer returned by this function or pass it to another function that could delete it, including creating QSharedPointer or QWeakPointer objects.
Whereas, if i were to use
Code:
Data* data as my private member class instead of QSharedPointer;
I will not need to worry if the caller do as follow
Code:
Data * data = new Data();
Data *data2 = myGadgets.GetData();
data2 = data;
delete data;
int sift(int a[], int b[], int n, int p) {
int i,k,x, tmp,index=0,count=0;
for(x=0; x<n; ++x)
b[x]=a[x];
[Code] .....
This is a function for a quicksort... Everything works; however, when I return index it returns the value for 'n'... I printed the value for index right before the function returns it and its 4, as it should be.
I have a program that is trying to find all factors of an integer given. It needs to be done in a recursion function. Right now i have code similar to just getting the prime factors of a integer.
unsigned int * find_factors_using_recursion(unsigned int x ) {
unsigned int * factor = new unsigned int[];//do i put x in here ?
for(unsigned int i = 2; i < x; ++i) {
if(x % i == 0) {
find_factors_using_recursion(x / i);
*factor = (factor[i] = i);
} }
return factor;
delete [] factor;
}
When i cout the *factor = (factor[i] = i) it gives me the prime numbers of the integer passed into the function but when I return the pointer it only returns one of the prime numbers. I'm new to c++, how to return pointers from functions that would be great with an example to go with it.
I know how to pass a 2-D array to a function. The prototype for that is void f(int (*p)[2]) assuming the array is of integers and there are 2 columns in it.
However, if I wanted the same function to return a pointer to a 2-D array, what would be the prototype?