Dynamic Array Allocation Random Crashing

Question

I've been trying to learn about pointers and allocating space during runtime. I decided to change one of my older assignments, a weather temperature array into a dynamically allocated array. I think I am close to being done but everytime I run it and enter a temperature my program crashes with no warning. I want to understand why it is crashing.

int dayNumber;
double fahrenheit = 0;
double cTemperature = 0;
const double MAXIMUM_TEMPERATURE = 60;// constants for mix/max
const double MINIMUM_TEMPERATURE = -90 ;
const int MAXIMUM_DAYS = 365;
const int MINIMUM_DAYS = 1;
double *ptrTemperatures;

cout << "How many days would you like to enter? ";
dayNumber = myValidation::GetValidInteger(MINIMUM_DAYS, MAXIMUM_DAYS);
try
{
    double *ptrTemperatures = new double[dayNumber];
}
catch(exception e)
{
    cout << "Failed to allocate memory: " << e.what() << endl;
}
cout << "\n\nTEMPERATURE REPORTER\n____________________________\n Please Enter the temperature for each day.";

for(int dayCount = 0; dayCount < dayNumber; dayCount++){
    cout << "Celsius Temperature for Day " << (dayCount + 1) << ": ";
    ptrTemperatures[dayCount] = myValidation::GetValidDouble(MINIMUM_TEMPERATURE, MAXIMUM_TEMPERATURE);
}





delete[] ptrTemperatures;
return 0;

You have two different variables called ptrTemperatures. — Stack Exchange Broke The Law
– Stack Exchange Broke The Law, Commented Mar 22, 2015 at 23:25
I've rolled back your recent changes, as, by removing the original problem, you made the existing answers incorrect. If you have more problems, please ask a new question. — Simon MᶜKenzie
– Simon MᶜKenzie, Commented Mar 22, 2015 at 23:56
Your variables dayCount and dayNumber are confusing. You're storing the count of days in dayNumber, but the current day number in dayCount. — Cole Tobin
– Cole Tobin, Commented Mar 23, 2015 at 0:10

user0815 · Accepted Answer · 2015-03-22 23:14:56Z

2

You should change your allocation as follows:

try
{
   ptrTemperatures = new double[dayNumber];
}

edited Mar 22, 2015 at 23:14

answered Mar 22, 2015 at 22:52

user0815

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1 Comment

Ryan Over a year ago

This fixed the random crashing. Thanks

Jonathan Potter · Accepted Answer · 2015-03-22 22:51:53Z

0

You're declaring a new variable called ptrTemperatures inside your try clause. This is the one you're allocating. The variable outside the try remains unallocated and uninitialized, so you are accessing random memory.

answered Mar 22, 2015 at 22:51

Jonathan Potter

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1 Comment

Ryan Over a year ago

I get what you mean, the visual below helped me realize what you meant. Thanks for the help :)

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