3.2 Preprocessor directives layout

• The preprocessor directive mark (#) MUST appear on the first column.
• Preprocessor directives following #if and #ifdef MUST be indented by one character:

            #ifndef DEV_BSIZE
            # ifdef BSIZE
            #  define DEV_BSIZE BSIZE
            # else /* !BSIZE */
            #  define DEV_BSIZE 4096
            # endif /* BSIZE */
            #endif /* !DEV_BSIZE */
       

• As shown in the previous example, #else and #endif SHOULD be followed by a comment describing the corresponding initial condition.
• The pre-processor MUST NOT be used to split a token. For instance, doing this:

            in\
            t ma\
            in ()
            {
            }
       

  is strongly forbidden.

• Trigraphs and digraphs MUST NOT be used.