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Just read on an internal university thread: #include <iostream> using namespace std; union zt { bool b; int i; }; int main() { zt w; bool a,b; a=1; b=2; cerr<<(bool)2<<static_cast<bool>(2)<<endl; //11 cerr<<a<<b<<(a==b)<<endl; //111 w.i=2; int q=w.b; cerr<<(bool)q<<q<<w.b<<((bool)((int)w.b))<<w.i<<(w.b==a)<<endl; //122220 cerr<<((w.b==a)?'T':'F')<<endl; //F } So a , b and w.b are all declared as bool . a is assigned 1 , b is assigned 2 , and the internal representation of w.b is changed to 2 (using a union ). This way all of a , b and w.b will be true , but a and w.b won't be equal, so this might mean that the universe is broken ( true!=true ) I know this problem is more theoretical than practical (a sake programmer doesn't want to change the internal representation of a bool ), but here are the questions: Is this okay? (this was tested with g++ 4.3.3) I mean, should the compiler be aware that during boolean comparison any non-zero value might mean true? Do you know any case where this corner case might become a real issue? (For example while loading binary data from a stream) EDIT: Three things: bool and int have different sizes, that's okay. But what if I use char instead of int . Or when sizeof(bool)==sizeof(int) ? Please give answer to the two questions I asked if possible. I'm actually interested in answers to the second

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