### Author:  [@DavidA](https://discourse.cmake.org/u/DavidA)
#### Post date: [April 6, 2022, 4:53pm UTC](https://discourse.cmake.org/t/pattern-for-choosing-compiler-options-based-on-toolchain/5388/1 "2022-04-06T16:53:11Z")
I need to set different compiler options (using target\_compile\_options) depending on which toolchain is used.
What is the recommended pattern for doing so? Should I do something like this in CMakeLists.txt?
```auto
if("${CMAKE_TOOLCHAIN_FILE}" STREQUAL "gnu_arm_toolchain.cmake")
target_compile_options(${EXECUTABLE} PRIVATE
-mcpu=cortex-m4
)
endif()
```
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [April 6, 2022, 10:55pm UTC](https://discourse.cmake.org/t/pattern-for-choosing-compiler-options-based-on-toolchain/5388/2 "2022-04-06T22:55:12Z")
I would not assume any particular toolchain file is used unless you are in a company environment where the toolchain files are prescribed (i.e. you have to use theirs and only theirs).
For problems like the one you describe, I usually first look at whether I can use `CMAKE_SYSTEM_NAME` to tell me enough about the target platform. In this case, it looks like you’re targeting an embedded platform, so I wouldn’t expect `CMAKE_SYSTEM_NAME` to be all that useful. It could be anything, since there’s no real convention for most embedded platforms, except maybe `Generic`, which isn’t of use to you anyway. Similarly, `CMAKE_SYSTEM_PROCESSOR` is conceptually what you should be looking for, but it is very unreliable and toolchain files rarely bother to set it. Even if they did, the contents can be pretty arbitrary.
It really comes down to where might the toolchain files come from. If you want to give the user freedom to use their own toolchain file, then you can’t use the name of the toolchain file as a determinant. You could, however, potentially require the toolchain file to set a particular variable and also require that variable to have one of a prescribed set of values. That variable might be `CMAKE_SYSTEM_PROCESSOR`, or it might be your own custom project-specific variable. I’ve seen this used in one company’s mono repo, where it provides a set of toolchain files, but you could still use your own if you wanted to.
---
### Author:  [@benthevining](https://discourse.cmake.org/u/benthevining)
#### Post date: [April 6, 2022, 11:47pm UTC](https://discourse.cmake.org/t/pattern-for-choosing-compiler-options-based-on-toolchain/5388/3 "2022-04-06T23:47:44Z")
Based just on the example above, it looks like the options need to be set if the compiler is GCC and the target platform is ARM. Can’t this be achieved almost entirely with generator expressions?
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [April 6, 2022, 11:52pm UTC](https://discourse.cmake.org/t/pattern-for-choosing-compiler-options-based-on-toolchain/5388/4 "2022-04-06T23:52:07Z")
You can detect the compiler reasonably reliably with generator expressions, but not the processor/platform. There’s no authoritative list of processor names, so you could get anything, or nothing at all.
---
### Author:  [@DavidA](https://discourse.cmake.org/u/DavidA)
#### Post date: [April 7, 2022, 8:03am UTC](https://discourse.cmake.org/t/pattern-for-choosing-compiler-options-based-on-toolchain/5388/5 "2022-04-07T08:03:51Z")
@craig.scott @benthevining Thank you both for your answers.