---
title: Warning C26453
description: "Describes the causes of MSVC code analysis warning C26453, and shows how to fix it."
ms.date: 07/15/2020
f1_keywords: ["C26453", "LEFTSHIFT_NEGATIVE_SIGNED_NUMBER"]
helpviewer_keywords: ["C26453"]
---
# Warning C26453

> Arithmetic overflow: Left shift of a negative signed number is undefined behavior (io.4)

## Remarks

This warning indicates the code left shifts a negative signed integral value, which is non-portable and triggers implementation defined behavior.

Code analysis name: `LEFTSHIFT_NEGATIVE_SIGNED_NUMBER`

## Example

```cpp
void leftshift(int shiftCount)
{
  const auto result = -1 << shiftCount;  // C26453 reported here

  // code
}
```

To correct this warning, use the following code:

```cpp
void leftshift(int shiftCount)
{
  const auto result = static_cast<unsigned>(-1) << shiftCount; // OK

  // code
}
```

## See also

[ES.102: Use signed types for arithmetic](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Res-unsigned)