# PR_EXTERN

Used to define the prototypes for functions or variables that are to be
exported from a shared library.

## Syntax

```{code}
#include <prtypes.h>

PR_EXTERN(type)prototype
```

## Description

{ref}`PR_EXTERN` is used to define externally visible routines and globals.
For syntax details for each platform, see
{searchfox}`prtypes.h <nsprpub/pr/include/prtypes.h>`.
The macro includes the proper specifications to declare the target
`extern` and set up other required linkages.

:::{warning}
**Warning**: Some platforms do not allow the use of the underscore
character (\_) as the first character of an exported symbol.
:::