Question

let’s say we have a c++ class like:

class MyClass {    void processArray( <an array of 255 integers> )    {      int i ;      for (i=0;i<255;i++)      {         // do something with values in the array      }    } } 

and one instance of the class like:

MyClass myInstance ; 

and 2 threads which call the processArray method of that instance (depending on how system executes threads, probably in a completely irregular order). There is no mutex lock used in that scope so both threads can enter.

My question is what happens to the i ? Does each thread scope has it’s own ‘i’ or would each entering thread modify i in the for loop, causing i to be changing weirdly all the time.

Answer 1

i is allocated on the stack. Since each thread has its own separate stack, each thread gets its own copy of i.