# PR_AtomicSet

Atomically sets a 32-bit value and return its previous contents.

## Syntax

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

PRInt32 PR_AtomicSet(
  PRInt32 *val,
  PRInt32 newval);
```

### Parameters

The function has the following parameter:

`val`

: A pointer to the value to be set.

`newval`

: The new value to assign to the `val` parameter.

### Returns

The function returns the prior value of the referenced variable.

## Description

{ref}`PR_AtomicSet` first reads the value of var, then updates it with the
supplied value. The returned value is the value that was read*before*
memory was updated. The memory modification is unconditional--that is,
it isn't a test and set operation.