---
description: "Learn more about the runtime_checks pragma directive in Microsoft C/C++"
title: "runtime_checks pragma"
ms.date: 01/22/2021
f1_keywords: ["vc-pragma.runtime_checks", "runtime_checks_CPP"]
helpviewer_keywords: ["runtime_checks pragma", "pragma, runtime_checks"]
no-loc: ["pragma"]
---
# `runtime_checks` pragma

Disables or restores the [`/RTC`](../build/reference/rtc-run-time-error-checks.md) compiler option settings.

## Syntax

> **`#pragma runtime_checks( "`** [ *runtime-check-options* ] **`",`** { **`restore`** | **`off`** } **`)`**

## Remarks

You can't enable a run-time check that wasn't enabled by a compiler option. For example, if you don't specify **`/RTCs`** on the command line, specifying `#pragma runtime_checks( "s", restore)` won't enable stack frame verification.

The **`runtime_checks`** pragma must appear outside a function, and takes effect at the first function defined after the pragma is seen. The **`restore`** and **`off`** arguments turn options specified in the **`runtime_checks`** pragma on or off.

The *runtime-check-options* can be zero or more of the parameters shown in the following table.

### Parameters of the runtime_checks Pragma

| Parameter(s) | Type of run-time check |
|--------------------|-----------------------------|
| **`s`** | Enables stack (frame) verification. |
| **`c`** | Reports when a value is assigned to a smaller data type that results in a data loss. |
| **`u`** | Reports when a variable is used before it's defined. |

These parameters are the same ones used with the **`/RTC`** compiler option. For example:

```cpp
#pragma runtime_checks( "sc", restore )
```

Using the **`runtime_checks`** pragma with the empty string (**`""`**) is a special form of the directive:

- When you use the **`off`** parameter, it turns the run-time error checks listed in the table above, off.

- When you use the **`restore`** parameter, it resets the run-time error checks to the ones that you specified using the **`/RTC`** compiler option.

```cpp
#pragma runtime_checks( "", off )
/* runtime checks are off in this region */
#pragma runtime_checks( "", restore )
```

## See also

[Pragma directives and the `__pragma` and `_Pragma` keywords](./pragma-directives-and-the-pragma-keyword.md)