A preprocessing token is the minimal lexical element of the language in translation
phases 3 through 6.
The categories of preprocessing token are: header names,
placeholder tokens produced by preprocessing import
, and export-keyword
identifiers, preprocessing numbers, character literals (including user-defined character
literals), string literals (including user-defined string literals), preprocessing
operators and punctuators, and single universal-character-names
and non-whitespace characters that do not lexically
match the other preprocessing token categories.
If a single universal-character-name
does not match any of the other preprocessing token categories,
the program is ill-formed.
If a '
or a "
matches the last category, the behavior is undefined.
Preprocessing tokens can be
this consists of comments ([lex.comment]
), or whitespace
characters (space, horizontal tab, new-line, vertical tab, and
form-feed), or both.
As described in [cpp]
, in certain
circumstances during translation phase 4, whitespace (or the absence
thereof) serves as more than preprocessing token separation.
can appear within a preprocessing token only as part of a header name or
between the quotation characters in a character literal or