value   bits
       -----   ----
    T:   1     0001
after bit change
    T:   3     0011
T is true
T is false

#include <iostream>
#include <bitset>

using namespace std;

void set_bits_to_1(void* val){
  char *x = static_cast<char *>(val);

  for (int i = 0; i<2; i++ ){
    *x |= (1UL << i);
  }
}

int main(int argc,char *argv[])
{

  bool T = 3;

  cout <<"       value   bits " <<endl;
  cout <<"       -----   ---- " <<endl;
  cout <<"    T:   "<< T <<"     "<< bitset<4>(T)<<endl;

  set_bits_to_1(&T);


  bitset<4> bit_T = bitset<4>(T);
  cout <<"after bit change"<<endl;
  cout <<"    T:   "<< T <<"     "<< bit_T<<endl;

  if (T ){
    cout <<"T is true" <<endl;
  }

  if ( T == false){
    cout <<"T is false" <<endl;
  }


}

movzx   eax, BYTE PTR [rbp-33]
    test    al, al
    je      .L22

movzx   eax, BYTE PTR [rbp-33]
    xor     eax, 1
    test    al, al
    je      .L23

int foo(bool b, int i) {
    return i + b;
}

foo(bool, int):
        movzx   edi, dil
        lea     eax, [rdi+rsi]
        ret