CODEWITHSUNDEEP
c++pointerssizemax
ninbit
ninbit

Reputation: 529

Maximum number of pointer in one variable

In my project, there are one million inputs and I am supposed to take different numbers of inputs in order to compare sort/search algorithms. Everything was allright till I tried to take five hundread thousand inputs. Therefore, I have realized that I can't create five hundred thousand pointers to my class or even an integer type by using array. However, I can create five pointers with size of one hundred thousand.

If I didn't explain very well, just look these two codes;

int *ptr[500000]; // it crashes

int *ptr1[100000]; // it runs well
int *ptr2[100000];
int *ptr3[100000];
int *ptr4[100000];
int *ptr5[100000];

What is the reason of crashing? Is there a limiting or is it about memory? And of course, how can I fix it?

Upvotes: 1

Views: 753

Answers (1)

Graham Borland
Graham Borland

Reputation: 60701

You are trying to allocate a 500,000-entry array on the stack. The stack is not really designed for holding large amounts of data like this. In your case, the stack just happens to be big enough to hold 100,000 entries (or even several different lots of 100,000 entries) but not 500,000 in a single block. If you overflow the stack, behaviour is undefined but a crash is likely.

You will get much better results by allocating your array on the heap instead.

int **ptr = malloc(500000*sizeof(int*));

Remember to check for a NULL return value from malloc, and free the memory when you're finished with it.

Upvotes: 1

Related Questions