Editing C preprocessor (section)

====Token stringification operator====
The '''stringification operator''' (a.k.a. stringizing operator), denoted by <code>#</code> converts a token into a [[string literal]], escaping any quotes or backslashes as needed. For definition:

<syntaxhighlight lang="cpp">
#define str(s) #s
</syntaxhighlight>

<code>str(\n)</code> expands to <code>"\n"</code> and <code>str(p = "foo\n";)</code> expands to <code>"p = \"foo\\n\";"</code>.

If stringification of the expansion of a macro argument is desired, two levels of macros must be used. For definition:

<syntaxhighlight lang="cpp">
#define xstr(s) str(s)
#define str(s) #s
#define foo 4
</syntaxhighlight>

<code>str(foo)</code> expands to "foo" and <code>xstr(foo)</code> expands to "4".

A macro argument cannot be combined with additional text and then stringified. However, a series of adjacent string literals and stringified arguments, also string literals, are concatenated by the C compiler.