In the example you gave, any compiler from the last 10 years would have given a warning message when converting the pointer to an int. Ignoring error messages is extremely, extremely bad practice. If you are still doing that, I suggest auditing your code right now to see if there are more problems such as mismatched printf arguments and so forth.

bool is a bad thing in C and C++, because of the implicit conversion rules. In C++, pointers implicitly convert to bool in every context-- there is never any warning message. This effectively reduces the compiler's ability to typecheck your program, since so many variables are pointers already, and C++ will happily stuff them into any bool argument to a function.

It seems like the C99 _Bool type implements the same implicit type conversion brain damage. That makes it a step backwards in terms of type safety, not forwards. That's right, using the old-fashioned, fuddy-duddy, plain old int and 0 and 1 gives you better type checking than the shiny new C++ feature.

As Linux points out, the worse typechecking comes with a side order of compatibility problems. And it is not any more efficient or readable.