As above post describe , bool is 8 bit long.
So is it possible to send value 2 in bool variable.
i.e.
0000 0010 -> 2
(decimal representation)
eg: bool x;
How to send this '2' in above bool variable 'x' ?
Thanks
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you could try `reinterpret_cast
(x) = 2;` But really, you should not use bool at all if you want to set 2 to a variable. – user1095108 Sep 21 '16 at 07:59 -
You could, but once you execute that, the behaviour is undefined. *Anything* can happen. – Martin Bonner supports Monica Sep 21 '16 at 08:05
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4It is 8 bits long on some guy's system. Read the post you linked. – juanchopanza Sep 21 '16 at 08:05
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To be honest, for this question it's sufficient that `bool` is _at least_ 8 bits, and _that_ statement is correct everywhere. – MSalters Sep 21 '16 at 10:53
2 Answers
8
Not in C++, no. A bool can hold true or false. There is no way to store 2 in a bool without first invoking undefined behaviour. Once you have invoked undefined behaviour, anything can happen. (Including what you expected except when demo'ing to important clients).
Also, a bool is not necessarily 8 bits long. It must be at least as large as a char (because sizeof(bool) must be at least 1), and the limits on the range of values which an unsigned char can hold means that it must be at least 8 bits. OTOH, there is nothing to stop an implementation using a bool which is larger than char, and there actually are implementations where char is 32 or 64 bits (DSP chips in the main).
Martin Bonner supports Monica
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I don't know, but I imagine the std::vector
specialisation could use less than 1 byte per element. – Matt Sep 21 '16 at 08:10 -
2@Matt: That is true, but it doesn't contain actual `bool` variables (**spit!**). – Martin Bonner supports Monica Sep 21 '16 at 08:11
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bool is 8 bits long
Not necessarily true. All the standards say is that it has to be capable of holding true and false: its sizeof is implementation defined. You can deduce that it must be at least 1 since the type of sizeof must be an integral type and it cannot be zero else pointer arithmetic on an array of bools would break.
So don't attempt to send the value 2 - you're bound to render the behaviour of your program undefined.
Bathsheba
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3Actually, a bool has to be *at least* 8 bits -sizeof is indeed implementation defined, but it has to be at least 1, and char must be at least 8 bits. – Martin Bonner supports Monica Sep 21 '16 at 08:06
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