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Heap overflow and Stack overflow in C
Heap Overflow
Heap is used to store dynamic variables. It is a region of process’s memory. malloc(), calloc(), resize() all these inbuilt functions are generally used to store dynamic variables.
Heap overflow occurs when −
A) If we allocate dynamic large number of variables −
int main() {
float *ptr = (int *)malloc(sizeof(float)*1000000.0));
}B) If we continuously allocate memory and do not free after using it.
int main() {
for (int i=0; i<100000000000; i++) {
int *p = (int *)malloc(sizeof(int));
}
}Stack Overflow
Stack is a Last in First out data structure. It is used to store local variables which is used inside the function. Parameters are passed through this function and their return addresses.
If a program consumes more memory space, then stack overflow will occur as stack size is limited in computer memory.
Stack overflow occurs when −
C) If a function is called recursively by itself infinite times then stack will be unable to store large number of local variables, so stack overflow will occur −
void calculate(int a) {
if (a== 0)
return;
a = 6;
calculate(a);
}
int main() {
int a = 5;
calculate(a);
}D) If we declare a large number of local variables or declare a large dimensional array or matrix can result stack overflow.
int main() {
A[20000][20000]
}
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