I read that booleans in C first came with C99. Now I wonder why bool nevertheless gets colored by Xcode's syntax highlighting, or what you call it...
When one searches "dial" in the build settings in Xcode, the "Language Dialect" pops up, and there I "dial-in" the C89 standard, and still bool gets colored.
Why is that?
I also read this:
Using boolean values in C
and I see how they did it, but I also don't understand how Example 3 and 4 works...
Option 3
typedef int bool;
enum { false, true };
Option 4
typedef int bool;
#define true 1
#define false 0
Note: I don't understand how the typedef int bool; could in anyway be connected with the line enum { false, true };.
Why is xcode with C89 not ignoring the bool keyword?
How do the examples work?
The syntax highlighting is an approximation used by XCode; it's not guaranteed to follow any standard. Not to say the syntax highlighting in XCode is not fairly advanced, but it would be very difficult to tell without compiling for a specific standard, what the symbols mean exactly, in real-time.
In the case of Option 3, it's performing an implicit conversion from an anonymous enum to an int. Since they are compatible types, it is "always a no-op and does not change the representation." The default enum values for { false, true } are { 0, 1 }, so this should result in the same assembler output. This answer has the order of preference when one doesn't know what to pick.