# FASTBuild generator refuses duplicated \`POST\_BUILD\` entry

**URL:** https://discourse.cmake.org/t/fastbuild-generator-refuses-duplicated-post-build-entry/15403
**Category:** Development
**Created:** [December 15, 2025, 4:47pm UTC](https://discourse.cmake.org/t/fastbuild-generator-refuses-duplicated-post-build-entry/15403 "2025-12-15T16:47:39Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![objectx](https://discourse.cmake.org/user_avatar/discourse.cmake.org/objectx/32/1067_2.png) [@objectx](https://discourse.cmake.org/u/objectx)
#### Post date: [December 15, 2025, 4:47pm UTC](https://discourse.cmake.org/t/fastbuild-generator-refuses-duplicated-post-build-entry/15403/1 "2025-12-15T16:47:39Z")

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`cmake -G FASTBuild` refuses duplicated `POST_BUILD` custom\_commands.

I’ve created a simplified example [here](https://github.com/objectx/cmake-fastbuild).

It seems that the label creation algorithm for `add_custom_command` depends on its contents and the exact same content creates the same labels.

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### Author: ![ben.boeckel](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [February 9, 2026, 5:22am UTC](https://discourse.cmake.org/t/fastbuild-generator-refuses-duplicated-post-build-entry/15403/2 "2026-02-09T05:22:21Z")

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@Eduard_Voronkin

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### Author: ![objectx](https://discourse.cmake.org/user_avatar/discourse.cmake.org/objectx/32/1067_2.png) [@objectx](https://discourse.cmake.org/u/objectx)
#### Post date: [April 16, 2026, 1:35pm UTC](https://discourse.cmake.org/t/fastbuild-generator-refuses-duplicated-post-build-entry/15403/3 "2026-04-16T13:35:24Z")

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CMake 4.3.1 still has the same issue.