C.7 Preprocessor

#define identifier token-string #define identifier ( identifier , ... , identifier ) token-string

#include "filename"
#include <filename>

#line constant "filename"opt
#undef identifier

conditional:
if-part elif-partsopt else-partopt endif-line

if-part:
if-line text

if-line:
# if constant-expression
# ifdef identifier
# ifndef identifier

elif-parts:
elif-line text
elif-parts elif-line text

elif-line:
# elif constant-expressionelse-part:
else-line text

else-line:
# else

endif-line:
# endif