Preprocessor Grammar

#define identifier token-string_opt

#define identifier[( identifier_opt, ... , identifier_opt )] token-string_opt

defined( identifier )

defined identifier

#include "path-spec"

#include <path-spec>

#line digit-sequence "filename"_opt

#undef identifier

#error token-string

#pragma token-string

conditional :

if-part elif-parts_opt else-part_opt 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-expression

else-part :

else-line text

else-line :

#else

endif-line :

#endif

digit-sequence :

digit
digit-sequence digit

digit : one of

0 1 2 3 4 5 6 7 8 9

token-string :

String of tokens

token :

keyword
identifier
constant
operator
punctuator

filename :

Legal operating system filename

path-spec :

Legal file path

text :

Any sequence of text

Note   The following nonterminals are expanded in Appendix A, Grammar Summary, of the C++ Language Reference: constant, constant-expression, identifier, keyword, operator, and punctuator.