# Fail cmake if there are unused variables defined
**URL:** https://discourse.cmake.org/t/fail-cmake-if-there-are-unused-variables-defined/840
**Category:** Usage
**Created:** [March 21, 2020, 4:54pm UTC](https://discourse.cmake.org/t/fail-cmake-if-there-are-unused-variables-defined/840 "2020-03-21T16:54:57Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@shukron](https://discourse.cmake.org/u/shukron)
#### Post date: [March 21, 2020, 4:54pm UTC](https://discourse.cmake.org/t/fail-cmake-if-there-are-unused-variables-defined/840/1 "2020-03-21T16:54:57Z")
Hi all!
I want make cmake fail if there are some unused variables defined.
Currently I do get a warning, but I couldn’t find a way to cause cmake exit with non-zero return value.
For example, I want the following invocation to fail:
```auto
cmake -S . -B build -DSOME_UNUSED_VAR=ON
```
I tried with both `-Wdev -Werror=dev` but it did not help.
Any ideas?
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [March 21, 2020, 9:11pm UTC](https://discourse.cmake.org/t/fail-cmake-if-there-are-unused-variables-defined/840/2 "2020-03-21T21:11:29Z")
The `--warn-unused-*` flags predate the `-Wdev` mechanism. It could be converted over to be `-W` flags with `-Werror=` alternatives for consistency. I know I don’t have time to work on the change, but an issue and/or MR for it would be the place to start.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [November 9, 2020, 8:32pm UTC](https://discourse.cmake.org/t/fail-cmake-if-there-are-unused-variables-defined/840/3 "2020-11-09T20:32:43Z")
I’ve filed [an issue](https://gitlab.kitware.com/cmake/cmake/-/issues/21412).