Are comments always processed before the preprocessor? [duplicate]

Question

/*
#define FOO
*/

#ifdef FOO
#define BAR "pirate"
#else
#define BAR "ninja"
#endif

int main() { printf(BAR); getchar(); }

In this code FOO is not defined (Visual Studio 2008). I assume that comments are processed first, then preprocessor, and then code. Are comments always processed before the preprocessor? Is this part of a standard?

Answer 1

I assume that comments are processed first, then preprocessor, and then code. Are comments always processed before the preprocessor?

Sort of -- part of the preprocessor's job is to remove comments. In this case, it doesn't care that you have the directive inside the comments; it's still removed just like any other comment.

Answer 2

According to the C standard, there are 8 translation phases during translation (compilation) of a program. Each comment is replaced by a whitespace character in translation phase 3, whereas preprocessing directives are executed in phase 4.