# Is there a downside for a toolchain to set vars in cache instead of \_INIT?
**URL:** https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034
**Category:** Usage
**Created:** [September 28, 2024, 11:01am UTC](https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034 "2024-09-28T11:01:46Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@redbaron](https://discourse.cmake.org/u/redbaron)
#### Post date: [September 28, 2024, 11:01am UTC](https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034/1 "2024-09-28T11:01:46Z")
One of game console vendor official toolchains sets variables like `CMAKE_CXX_FLAGS` as `CACHE` vars, instead of setting `CMAKE_CXX_FLAGS_INIT` and let CMake propagate it.
I found it when tried to create wrapper for vendor toolchain and saw that my updates to `CMAKE_CXX_FLAGS_INIT` has no effect. Did they create toolchain incorrectly then? What is the downside of settings cache vars directly instead of (as I understand it) recommended approach of setting just `_INIT` vars.
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [September 28, 2024, 9:22pm UTC](https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034/2 "2024-09-28T21:22:56Z")
Setting the `CMAKE__FLAGS_INIT` variables is the more correct thing to do. If a toolchain file sets `CMAKE__FLAGS` instead, there are a few consequences:
- Depending on what policies the project has set, this can discard a variable by the same name if it has already been set by the user or the project.
- If the toolchain file is using `FORCE` when setting `CMAKE__FLAGS`, it will discard any cache variable set by the user. This can hinder the user from doing things like experimenting with flags (e.g. different debugging levels or info formats), or adding flags for use cases the toolchain file didn’t consider (e.g. using sanitisers).
- It prevents CMake from providing its standard set of flags. The `CMAKE__FLAGS_INIT` variables are usually _combined_ with default values CMake gives.
There are scenarios where a user might need to set `CMAKE__FLAGS` in a toolchain file to achieve a particular set of flags. If a vendor is supplying a toolchain file, they can’t know all the scenarios a user may face, so the vendor should not force the flags with `CMAKE__FLAGS`. They should use `CMAKE__FLAGS_INIT` instead, unless the default flags CMAKE automatically combines them with are known to cause problems.
---
### Author:  [@redbaron](https://discourse.cmake.org/u/redbaron)
#### Post date: [September 30, 2024, 8:56am UTC](https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034/3 "2024-09-30T08:56:49Z")
I was incorrect in my initial assessment, `_FLAGS` vars are _not_ set as `CACHE FORCE`, but just as normal vars. I suppose this way users are still free to experiment with flags after project was first configured. Vendor do set other vars as `CACHE FORCE`, like `CMAKE_CXX_COMPILER`, but I guess that is fine because those vars 100% should never be altered by user (that’s the purpose of the toolchain after all).
It leaves downside of not being able to provide initial set of vars in `CMAKE_CXX_FLAGS_INIT` as a configure option, but it can be mitigated by adding `add_compile_options` early in CMakeLists.txt file.
As for default flags CMake might be adding, what they could be? Vendor ships toolchain with custom `CMAKE_SYSTEM_NAME`, so unlikely CMake can/should have any meaningful defaults.
Overall, without `CACHE FORCE` their approach doesn’t have much downside I can see. I’ll still open support request asking to switch to a recommended way of using `_INIT` vars, but case to do so is not as strong as I thought initially.
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [September 30, 2024, 10:06pm UTC](https://discourse.cmake.org/t/is-there-a-downside-for-a-toolchain-to-set-vars-in-cache-instead-of-init/12034/4 "2024-09-30T22:06:37Z")
> [@redbaron](#):
>
> As for default flags CMake might be adding, what they could be? Vendor ships toolchain with custom `CMAKE_SYSTEM_NAME`, so unlikely CMake can/should have any meaningful defaults.
It depends on the toolchain. For example, it is common for embedded toolchains from vendors to be based on gcc or clang. While the toolchain might be targeting some less common processor or architecture, CMake will still recognise them as a gcc or clang compiler and set up appropriate default flags for debugging, optimisation, etc.