What advantage does _Bool give?

Question

If the _Bool type acts like an integer and doesn't enforce that a value is true/false or 1/0, for example:

_Bool bools[] = {0,3,'c',0x17};
printf("%d", bools[2]);

> 1

What is the advantage of having that there? Is it just a simple way to coerce things to see how they would evaluate for 'truth-ness', for example:

printf("%d\n", (_Bool) 3);
> 1

Or how is this helpful or useful in the C language?

Answer 1

What advantage does _Bool give?

1. The value of a _Bool is either 0 or 1. Nothing else, unlike an int.

2. Conversion to a _Bool always converts non-zero to 1 and only 0 to 0.

When any scalar value is converted to _Bool, the result is 0 if the value compares equal to 0; otherwise, the result is 1.

Examples:

#include <math.h>
#include <stdlib.h>
_Bool all_false[] = { 0, 0.0, -0.0, NULL };
_Bool all_true[] = { 13, 0.1, 42.0, "Hello", NAN };

Notice the difference of conversion/casting to int vs; _Bool: (int) 0.1 --> 0, yet (_Bool) 0.1 --> 1.

Notice the difference of conversion/casting to unsigned vs; _Bool: (unsigned) 0x100000000 --> 0, yet (_Bool) 0x100000000 --> 1.

3. _Bool adds clarity to boolean operations.

4. _Bool is a distinctive type from int, char, etc. when used with _Generic.

5. Prior to C99, C lacked _Bool. Much early code formed their own types bool, Bool, boolean, bool8, bool_t, .... Creating a new type _Bool brought uniformity to this common, yet non-uniform practice. <stdbool.h> is available to use bool, true, false. This allows older code, which does not include <stdbool.h> to not break, yet newer code to use cleaner names.

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OP's example with "doesn't enforce that a value is true/false or 1/0" does enforce that bools[2] had a value of 1. It did not enforce that the initializer of 'c', an int, had to be in the range of [0...1] nor of type _Bool, much like int x = 12.345; is allowed. In both cases, a conversion occurred. Although the 2nd often generates a warning.