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Printing an uninitialized bool using cout (C++)

Answer 1

+14 A:

Is this behavior compliant with the standard?

Yes! Using garbage values(uninitialized) in your code invokes Undefined Behavior

Prasoon Saurav 2010-01-28 11:40:25

Answer 2

+4 A:

Yes. An uninitialized variable can have any value.

KennyTM 2010-01-28 11:40:27

It is difficult to talk about values in the presence of undefined behavior. `bool` only has two possible values, `false` and `true`. The fact that `cout << b` outputs something other than `0` and `1` is a consequence of the behavior not being defined, not of `b` having a "value" other than `false` or `true`.

avakar 2010-01-28 11:51:06

True. It could also print nothing at all, 0.5, "blue", or emit smoke

MSalters 2010-01-28 12:01:58

You could turn into a cat. Demons could fly out of your nose.

jleedev 2010-01-28 12:34:59

Answer 3

A:

As soon as "<<" operator does not check the bool, this behavior is correct.
The problem here is hidden in the bool itself: program uses more than one bit to store the bool. This is dependent on implementation. Sometimes only one bit can be used to store the bool.
Sometimes more, and it is such a case.

avp 2010-01-28 13:30:48

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Printing an uninitialized bool using cout (C++)

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