# CMakePresets: What is the overwrite order for multiple inheritance?
**URL:** https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775
**Category:** Code
**Created:** [August 19, 2023, 8:10pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775 "2023-08-19T20:10:13Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [August 19, 2023, 8:10pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/1 "2023-08-19T20:10:13Z")
I have the CMakeUserPreset.json:
```json
{
"version": 6,
"cmakeMinimumRequired": {
"major": 3,
"minor": 25,
"patch": 0
},
"configurePresets": [
{
"name": "dev",
"displayName": "developer Ninja build on macos with Coverage",
"inherits": ["ci-darwin", "coverage-darwin"],
"generator": "Ninja"
}
],
"buildPresets": [
{
"name": "dev",
"configurePreset": "dev",
"configuration": "Coverage"
}
],
"testPresets": [
{
"name": "dev",
"configurePreset": "dev",
"configuration": "Coverage",
"output": {
"outputOnFailure": true
}
}
] ,
"workflowPresets": [
{
"name": "dev",
"steps": [
{
"type": "configure",
"name": "dev"
},
{
"type": "build",
"name": "dev"
},
{
"type": "test",
"name": "dev"
}
]
}
]
}
```
The `ci-darwin (Release build)` should be overwritten by `coverage-darwin`!
But the result is this:
```bash
bash-3.2$ cmake --workflow --preset dev --fresh
Executing workflow step 1 of 3: configure preset "dev"
Preset CMake variables:
CMAKE_BUILD_TYPE="Release"
CMAKE_CXX_EXTENSIONS="OFF"
CMAKE_CXX_FLAGS="-fstack-protector-strong -fcf-protection=full -Wall -Wextra -Wpedantic -Wconversion -Wsign-conversion -Wcast-qual -Wformat=2 -Wundef -Werror=float-equal -Wshadow -Wcast-align -Wunused -Wnull-dereference -Wdouble-promotion -Wimplicit-fallthrough -Wextra-semi -Woverloaded-virtual -Wnon-virtual-dtor -Wold-style-cast"
CMAKE_CXX_FLAGS_COVERAGE="-Og -g --coverage"
CMAKE_CXX_STANDARD="17"
CMAKE_CXX_STANDARD_REQUIRED="ON"
CMAKE_EXE_LINKER_FLAGS_COVERAGE="--coverage"
CMAKE_SHARED_LINKER_FLAGS_COVERAGE="--coverage"
ENABLE_COVERAGE="ON"
-- The CXX compiler identification is AppleClang 14.0.3.14030022
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY
-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY - Success
-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY
-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY - Success
-- Performing Test COMPILER_HAS_DEPRECATED_ATTR
-- Performing Test COMPILER_HAS_DEPRECATED_ATTR - Success
-- Configuring done (2.1s)
-- Generating done (0.0s)
CMake Warning:
Manually-specified variables were not used by the project:
CMAKE_CXX_FLAGS_COVERAGE
CMAKE_EXE_LINKER_FLAGS_COVERAGE
CMAKE_SHARED_LINKER_FLAGS_COVERAGE
ENABLE_COVERAGE
-- Build files have been written to: /Users/clausklein/Workspace/cpp/cmake-init-shared-static/build/coverage
Executing workflow step 2 of 3: build preset "dev"
[2/2] Linking CXX static library libshared.a
Executing workflow step 3 of 3: test preset "dev"
Test project /Users/clausklein/Workspace/cpp/cmake-init-shared-static/build/coverage
No tests were found!!!
bash-3.2$
```
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [August 19, 2023, 10:08pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/2 "2023-08-19T22:08:43Z")
> [@ClausKlein](#):
>
> The `ci-darwin (Release build)` should be overwritten by `coverage-darwin`!
No, that’s not how `inherits` works for presets. The presets documentation makes clear the behavior with the following statement:
> If multiple `inherits` presets provide conflicting values for the same field, the earlier preset in the `inherits` array will be preferred.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [August 20, 2023, 5:47am UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/3 "2023-08-20T05:47:16Z")
**That seems wrong to me!**
For single inheritance, the **last** preset overwrites a value.
So I expected the same rules for multiple preset inheritance in a list.
What is the reason for this **different** rules?
---
### Author:  [@crealsgachoud](https://discourse.cmake.org/u/crealsgachoud)
#### Post date: [January 23, 2024, 4:16pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/4 "2024-01-23T16:16:16Z")
Hi,
I believe they are considered two different concepts. The multiple inheritances is a “diamond shape”, but it seems to me you think about it as an inheritance chain.
Let’s say you have the preset “release”, “debug”, “env”. If you create “default” that inherits from “debug” which in turn inherits from “env” it is a chain of inheritance “default"→"debug"→"env”. However, if you put [“release”, “debug”] in the inheritance of “default”, “default” inherits from both at the same level. The rule of resolution has nothing to do with the inheritance overwrite and the order in which the inheritance priority should be decided is a new question entirely, so why not choose to put priority from left to right (from the start of the list to the end)?
I hope this answer helps you despite being a few months late!
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [January 30, 2024, 1:01pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/5 "2024-01-30T13:01:51Z")
I can’t follow your arguments?
For me, I would expect that` [release, debug, coverage]` will result in same cache values than
```auto
release
|
debug
|
coverage
```
### The last set values overwrite the previous one.
---
### Author:  [@crealsgachoud](https://discourse.cmake.org/u/crealsgachoud)
#### Post date: [January 31, 2024, 12:40pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/6 "2024-01-31T12:40:15Z")
If I understand correctly, you expect that [release, debug, coverage] would behave like if coverage was inheriting from debug, and debug from release. However, in a chain of inheritance, you do not have to choose between multiple values for a single variable. Let say coverage has CMAKE\_BUILD\_TYPE set to RELEASE, debug inherits from coverage and defines CMAKE\_BUILD\_TYPE to DEBUG. Then debug only contains one value for CMAKE\_BUILD\_TYPE, which is DEBUG. So if you would make “default” that inherits from debug, default would have DEBUG as value for CMAKE\_BUILD\_TYPE because there is no other choice.
If instead you define “default” as inheriting from [release, debug, coverage], then you are in a completely different situation, you might have 3 definitions of CMAKE\_BUILD\_TYPE and need to choose which one you are going to keep. Their choice was to put priority on the first one in the list, but they could have done the opposite.
I am not saying I agree or disagree with this choice, the argument is here only to try to explain that the rules do not differ between chained inheritance and multi-inheritance but rather that we have two different concepts that have their set of rules. I am trying to address your last question:
> What is the reason for this **different** rules?
I hope this makes it clearer.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [January 31, 2024, 7:15pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/7 "2024-01-31T19:15:03Z")
In the meantime, I am completely confused from cmake docu and discussion:
```rst
The preset will inherit all of the fields from the inherits presets by default
(except name, hidden, inherits, description, and displayName),
but can override them as desired.
```
Does this mean, there is no inheritance hierarchy possible with cmake presets?
If I want to merge values from different presets, I have to use an inheritance list?
---
### Author:  [@crealsgachoud](https://discourse.cmake.org/u/crealsgachoud)
#### Post date: [February 1, 2024, 8:19am UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/8 "2024-02-01T08:19:03Z")
I do not think so. Let’s say you have a preset “default” that inherits from “debug”. “debug” has CMAKE\_BUILD\_TYPE set to DEBUG, then “default” inherits the field CMAKE\_BUILD\_TYPE with value DEBUG. Therefore “debug” has the field CMAKE\_BUILD\_TYPE set to DEBUG. Thus, if you would now create a preset “custom” that inherits from “default”, “custom” would inherit CMAKE\_BUILD\_TYPE with value DEBUG from “default”. So, indirectly, “custom” inherits from “debug”, but “debug” is not in the inheritance field of “custom”. If it is not clear enough, consider this specification as a technicality and keep in mind that, “custom” inherits fields from “debug” unless they have been redefined in “default”, or in “custom”.
I hope it helps
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [February 1, 2024, 11:37am UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/9 "2024-02-01T11:37:31Z")
**IMHO** , the CMake preset documentation is not easy to understand.
_The handling of multiple inheritance is given, but without good reasons!_
A good example and a clear specification can be found [multiple inheritance and C3\_linearization](https://en.wikipedia.org/wiki/C3_linearization)
and [what is the exact order of constructors in a multiple and/or virtual inheritance situation?](https://isocpp.org/wiki/faq/multiple-inheritance#mi-diamond)
---
### Author:  [@crealsgachoud](https://discourse.cmake.org/u/crealsgachoud)
#### Post date: [February 1, 2024, 2:00pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/10 "2024-02-01T14:00:21Z")
Is it clearer for you now?
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [February 1, 2024, 4:15pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/11 "2024-02-01T16:15:05Z")
Yes, I work with multiple inheritance since years.
The problem is the missing consistent concept for `cmake presets inheritance rules`.
### There must also respect the condition results!
see i.e.:
```json
{
"version": 8,
"configurePresets": [
{
"name": "ninja-multi",
"hidden": true,
"generator": "Ninja Multi-Config",
"binaryDir": "${sourceDir}/build"
},
{
"name": "windows-only",
"inherits": "ninja-multi",
"hidden": true,
"condition": {
"type": "equals",
"lhs": "${hostSystemName}",
"rhs": "Windows"
},
"environment": {
"PLATFORM": "WINDOWS64"
}
},
{
"name": "unix-only",
"inherits": "ninja-multi",
"hidden": true,
"condition": {
"type": "notEquals",
"lhs": "${hostSystemName}",
"rhs": "Windows"
},
"environment": {
"PLATFORM": "POSIX64"
}
},
{
"name": "default",
"displayName": "Ninja Multi-Config",
"description": "Default build using Ninja Multi-Config generator",
"condition": {
"type": "const",
"value": true
},
"inherits": [
"windows-only",
"unix-only"
]
}
]
}
```
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [February 1, 2024, 4:18pm UTC](https://discourse.cmake.org/t/cmakepresets-what-is-the-overwrite-order-for-multiple-inheritance/8775/12 "2024-02-01T16:18:24Z")
see too [Condition field for workflow presets](https://discourse.cmake.org/t/condition-field-for-workflow-presets/6934)