Memory safety

But what do we mean by a program being memory safe? Memory safety is the idea that your program never touches a memory location it is not supposed to, and that the variables declared in your program cannot point to invalid memory and remain valid in all code paths. In other words, safety basically boils down to pointers having valid references all of the time in your program, and that the operations with pointers do not lead to undefined behavior. Undefined behavior is the state of a program where it has entered a situation that has not been accounted for in the compiler's because the compiler specification does not clarify what happens in that situation.

An example of undefined behavior in C is accessing out of bound and uninitialized array elements:

// uninitialized_reads.c

#include <stdio.h>
int main() { 
    int values[5]; 
    for (int i = 0; i < 5; i++) 
        printf("%d ", values[i]); 
}

In the preceding code, we have an array of 5 elements and we loop and print...