CODEWITHSUNDEEP
c++pointersstldeque
moooni moon
moooni moon

Reputation: 363

Issue settings value to deque pointer

#include <iostream>
#include <string.h>
#include <deque>

using namespace std;

void insertValues(deque<float*> mydeque)
{
    *mydeque.at(0)=12;
}

void initArray(deque<float*> mydeque, float* values)
{
    for(int i=0;i<3;i++)
        mydeque.push_back(values+i);
}

int main ()
{
    float values[3];
    deque<float*> mydeque;
    initArray(mydeque,values);

    insertValues(mydeque); //Gives out of range - memory error

    cout<<values<<" "<<values+1<<" " <<values[0]<<endl;
    values[0]=5;
    cout<<values<<" "<<values+1<<" " <<values[0]<<endl;

    getchar();

    return 0;
}

In the above code, i bump into memory issues on calling insertValues() function and it gives out of range error but i don't know why that happens because the deque has the correct addresses which i verified.

Where am i going wrong?

Upvotes: 0

Views: 68

Answers (1)

WhiZTiM
WhiZTiM

Reputation: 21576

Your problem is here.

void initArray(deque<float*> mydeque, float* values)
{
    for(int i=0;i<3;i++)
        mydeque.push_back(values+i);
}

mydeque is going to be a copy of whatever you passed, mydeque was filled and later destroyed. The originally passed parameter remains untouched. Modify it to take the parameter by reference...

void initArray(deque<float*>& mydeque, float* values)
{
    for(int i=0;i<3;i++)
        mydeque.push_back(new float(values+i);
}

Though your code will work as it is, but you should not use a std::deque of pointers to float. Its way too fragile and its less performant in time and memory. Prefer to use integral types by value.

Upvotes: 3

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