[cpp.stringize]

# 15 Preprocessing directives [[cpp]](./#cpp)

## 15.7 Macro replacement [[cpp.replace]](cpp.replace#cpp.stringize)

### 15.7.3 The # operator [cpp.stringize]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/preprocessor.tex#L1795)

Each# preprocessing token in the replacement list for a function-like
macro shall be followed by a parameter as the next preprocessing
token in the replacement list[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/preprocessor.tex#L1802)

A [*character string literal*](#def:character_string_literal "15.7.3 The # operator [cpp.stringize]") is a [*string-literal*](lex.string#nt:string-literal "5.13.5 String literals [lex.string]") with no prefix[.](#2.sentence-1)

If, in the replacement list, a parameter is immediately
preceded by a# preprocessing token,
both are replaced by a single character string literal preprocessing token that
contains the spelling of the preprocessing token sequence for the
corresponding argument (excluding placemarker tokens)[.](#2.sentence-2)

Let the [*stringizing argument*](#def:stringizing_argument "15.7.3 The # operator [cpp.stringize]") be the preprocessing token sequence
for the corresponding argument with placemarker tokens removed[.](#2.sentence-3)

Each occurrence of whitespace between the stringizing argument's preprocessing
tokens becomes a single space character in the character string literal[.](#2.sentence-4)

Whitespace before the first preprocessing token and after the last
preprocessing token comprising the stringizing argument is deleted[.](#2.sentence-5)

Otherwise, the original spelling of each preprocessing token in the
stringizing argument is retained in the character string literal,
except for special handling for producing the spelling of[*header-name*](lex.header#nt:header-name "5.6 Header names [lex.header]")*s*,[*character-literal*](lex.ccon#nt:character-literal "5.13.3 Character literals [lex.ccon]")*s*,
and [*string-literal*](lex.string#nt:string-literal "5.13.5 String literals [lex.string]")*s* (including the delimiting U+0022 quotation mark ("))
contained within the preprocessing token:
a U+005c reverse solidus character (\)
is inserted before each U+0022 quotation mark andU+005c reverse solidus character of a[*header-name*](lex.header#nt:header-name "5.6 Header names [lex.header]"),[*character-literal*](lex.ccon#nt:character-literal "5.13.3 Character literals [lex.ccon]"),
or [*string-literal*](lex.string#nt:string-literal "5.13.5 String literals [lex.string]"),
and each new-line character is
replaced by the two-character sequence \n[.](#2.sentence-6)

If the replacement that results is not a valid character string literal,
the program is ill-formed[.](#2.sentence-7)

The character string literal corresponding to
an empty stringizing argument is ""[.](#2.sentence-8)

The order of evaluation of# and## operators is unspecified[.](#2.sentence-9)