Question

I ran across some very interesting code that makes me wonder about what bool is. I’ve always considered it to be a primitive type, like int or char or long. But today, I saw something that looked like this:

void boolPtrTest()
{
    bool thisBool = true;

    boolPtrHere(thisBool);

    printf("thisBool is %s\n", thisBool ? "true" : "false");
}

void boolPtrHere(bool& theBool)
{
    theBool = false; // uhh, dereferencing anyone?
}

And this code runs – no errors – and prints “thisBool is false”!

To further make this odd, I ran the following code:

bool myBool = new bool();

…and the code ran fine!

Before you go and downvote me for asking a “noobish” question

Here’s my question: what is bool? Is it defined on an implementation-by-implementation basis? From the evidence shown above, I would say that it’s a class. From a practical standpoint (disregarding the above), it would also seem proper to define a bool as a typedef to an int / char or have it #define’d. But how does one know what it is, (which would affect how you would treat it)?

EDIT: I thought I’d add that I’m working in VS 2008.

Answer 1

void boolPtrHere(bool& theBool)
{
    theBool = false; // uhh, dereferencing anyone?
}

There is nothing wrong with this code. The bool is taken by reference. No dereferencing is required.

bool myBool = new bool();

new returns an address, which is converted to true, since it never returns a nonzero value. This is a common conversion, especially in C code:

int* my_int = malloc(10 * sizeof(int));
if (!my_int) // my_int is converted to bool
    memory_error();