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Diana Richards (v-dirichards) merged 2 commits into from
Aug 19, 2026
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atexit: Clarify DLL behavior is the same as _onexit #5952

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atexit: Clarify DLL behavior is the same as _onexit
jay Aug 11, 2026
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Revise atexit documentation for accuracy
TylerMSFT Aug 18, 2026
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4 changes: 3 additions & 1 deletion docs/c-runtime-library/reference/atexit.md
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@@ -1,7 +1,7 @@
---
description: "Learn more about: atexit"
title: "atexit"
ms.date: "11/04/2016"
ms.date: "8/18/2026"
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api_name: ["atexit"]
api_location: ["msvcrt.dll", "msvcr80.dll", "msvcr90.dll", "msvcr100.dll", "msvcr100_clr0400.dll", "msvcr110.dll", "msvcr110_clr0400.dll", "msvcr120.dll", "msvcr120_clr0400.dll", "ucrtbase.dll"]
api_type: ["DLLExport"]
Expand Down Expand Up @@ -36,6 +36,8 @@ The **`atexit`** function is passed the address of a function *`func`* to be cal

The code in the **`atexit`** function shouldn't contain any dependency on any DLL that could have already been unloaded when the **`atexit`** function is called.

**Microsoft-specific DLL behavior**: When a DLL unloads, after `DLLMain` receives `DLL_PROCESS_DETACH`, the DLL's `atexit` callbacks run in reverse registration order, with the last callback registered running first.

To generate an ANSI-conformant application, use the ANSI-standard **`atexit`** function (rather than the similar **`_onexit`** function).

## Requirements
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