modify_const.cpp

// Example of a constant being modified
// clang++ -Wall -std=c++17 -O2 -o modify_const modify_const.cpp

#include <iostream>
#include <string>
#include <sstream>

unsigned long long hex_to_dec(std::string str)
{
  unsigned long long result = 0;
  unsigned long long power = 1;
  for (int index = str.length() - 1; index > 1; --index) {
    int c = str.at(index);
    c -= std::isdigit(c) ? '0' : 'a' - 10;
    result += c * power;
    power *= 16;
  }
  return result;
}

int main()
{
  const int x[] = {1, 2, 3};
  std::cout << "Initial value of x[0] " << *x << '\n';
  const int* ptr = x;
  std::stringstream strm;
  strm << ptr;
  auto s = strm.str();
  unsigned long long result = hex_to_dec(s);
  int* y = (int*) result;
  std::cout << "Initial value of *y " << *y << '\n';
  *y = 1234;
  std::cout << "New value of *y " << *y << '\n';
  std::cout << "Addr x and y " << x << ' ' << y << '\n';
  std::cout << "New value of x[0] " << *x << '\n';
  return 0;
}