# 16 Preprocessing directives [cpp]

## 16.9 Pragma operator [cpp.pragma.op]

A unary operator expression of the form:

`_Pragma ( string-literal )`

is processed as follows: The string literal is destringized by deleting the L prefix, if present, deleting the leading and trailing double-quotes, replacing each escape sequence \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The resulting sequence of characters is processed through translation phase 3 to produce preprocessing tokens that are executed as if they were the pp-tokens in a pragma directive. The original four preprocessing tokens in the unary operator expression are removed.

Example:

```#pragma listing on "..\listing.dir"
```

can also be expressed as:

```_Pragma ( "listing on \"..\\listing.dir\"" )
```

The latter form is processed in the same way whether it appears literally as shown, or results from macro replacement, as in:

```#define LISTING(x) PRAGMA(listing on #x)
#define PRAGMA(x) _Pragma(#x)

LISTING( ..\listing.dir )
```

— end example ]