Array passed as arguement to a function showing garbage values

Question

here's the code:

int *num_arr = number_to_array(num);
cout<<"\nNum aaray:"<<*(num_arr+1);
display(num_arr, digit_count);

The cout statement here is showing the correct value, but display() is not. display is showing garbage values

code for display():

void display(int num_arr[],int dc)
{
cout<<"\n";
cout<<"\n"<<num_arr[0];
cout<<"\n"<<num_arr[1];
 for(int i = (dc-1); i>=0; i--)
 {
         cout<<num_arr[i];
 }

}

int* number_to_array(int num)
{
int i=0;
int num_arr[100]; // make dynamic array
  while(num!=0)
  {
    num_arr[i] = num%10;
    num  = num/10;                
    i++;
   }
return num_arr;
}

what could be the reason?

possible duplicate of [Returning Pointer from a Function in C++](http://stackoverflow.com/questions/8969292/returning-pointer-from-a-function-in-c) — Mat, Jul 11 '13 at 09:26

score 2 · Accepted Answer · edited Jul 11 '13 at 09:34

2

You are returning address of local variable (name of array is address of it's first element). It is mistake, because array will not exists after you exit a function.
int num_arr[100]; // make dynamic array - it is static array, not dynamic.

Possible solutions:

(Prefferable) Use std::vector
Use dynamic arrays (int *p = new int[100])

Proposal - learn basics of C/C++: pointers, arrays, function arguments and return values.

edited Jul 11 '13 at 09:34

awesoon

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answered Jul 11 '13 at 09:29

Dmitry Sazonov

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but why is the cout statement after the call to make array function showing the correct value? – user1995120 Jul 11 '13 at 09:35
It is just luck, that value in memory was not overwrited by another variables. – Dmitry Sazonov Jul 11 '13 at 09:37
@user1995120 because no one yet overwritten it - but it can happen at every millisecond – Arioch 'The Jul 11 '13 at 09:38
Btw, there are perfect article for Russian community: http://www.rsdn.ru/article/cpp/ObjectsAndPointers.xml – Dmitry Sazonov Jul 11 '13 at 15:23

Array passed as arguement to a function showing garbage values

1 Answers1