# CMake commands cause project build to walk entire drive.

**URL:** https://discourse.cmake.org/t/cmake-commands-cause-project-build-to-walk-entire-drive/2913
**Category:** Usage
**Created:** [March 7, 2021, 9:14pm UTC](https://discourse.cmake.org/t/cmake-commands-cause-project-build-to-walk-entire-drive/2913 "2021-03-07T21:14:31Z")
**Posts on this page:** 1
**Showing post:** 2

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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: [March 7, 2021, 10:17pm UTC](https://discourse.cmake.org/t/cmake-commands-cause-project-build-to-walk-entire-drive/2913/2 "2021-03-07T22:17:13Z")

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The comma? It’s a valid variable character (though one we could possibly deny as a literal name via a policy). This will still always work:

```cmake
set(varname "foo,")
set("${varname}" value)

```

That said…maybe one shouldn’t use `GLOB_RECURSE` for source file listings 🙂 . I, personally, [would never recommend it](https://discourse.cmake.org/t/is-glob-still-considered-harmful-with-configure-depends/808).

That said, there are warnings for unused/undefined variables you can ask for upon request (`--warn-unused` and `--warn-undefined`).

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