# How to include subdirectory with a different generator?

**URL:** https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594
**Category:** Usage
**Created:** [April 6, 2026, 11:16am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594 "2026-04-06T11:16:00Z")
**Posts on this page:** 11
**Page:** 1

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [April 6, 2026, 11:16am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/1 "2026-04-06T11:16:00Z")

</div>

Hello,

I have two working `CMakeList.txt` files -

`<project root>CMakeList.txt`

```auto

#[[

# build with shared prebuilt SDL3 library (DLL)

cmake -B build -G "Ninja Multi-Config"

cmake --build build

build\Debug\hello.exe

cmake --build build --config Release

build\Release\hello.exe

]]

cmake_minimum_required(VERSION 3.20)

project(hello)

set(CMAKE_C_COMPILER "C:/Program Files/LLVM/bin/clang.exe")

set(CMAKE_CXX_COMPILER "C:/Program Files/LLVM/bin/clang++.exe")

add_library(SDL3 SHARED IMPORTED)

set_target_properties(SDL3 PROPERTIES

INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_SOURCE_DIR}/SDL3-3.4.2/include"

IMPORTED_IMPLIB "${CMAKE_SOURCE_DIR}/SDL3-3.4.2/lib/x64/SDL3.lib" # SHARED

)

add_executable(${PROJECT_NAME} hello.cpp)

target_link_libraries(${PROJECT_NAME} SDL3)

#set(ENV{CMAKE_GENERATOR} Ninja)

#add_subdirectory(emscripten)

```

which builds a SDL3 Hello, World! C++ program using generator (-G) Ninja Multi-Config and

`<project root>/emscripten/CMakeList.txt`

```auto

#[[

cmake -B build -G Ninja

cmake --build build

python -m http.server 8000

http://localhost:8000

]]

cmake_minimum_required(VERSION 3.21)

set(CMAKE_TOOLCHAIN_FILE "../../emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake")

project(hello_wasm)

set(CMAKE_BUILD_TYPE MinSizeRel)

# Set the name of the future application (in Windows this would be app.exe, while for web it will be app.js / app.wasm)

add_executable(${PROJECT_NAME} ../hello.cpp)

# Tell CMake where to find the SDL3 library configuration files

set(SDL3_DIR install_libSDL3/lib/cmake/SDL3)

# Load SDL3 package settings (compilation parameters and paths to headers)

find_package(SDL3 REQUIRED)

# Link SDL3 to our application (configures linking and include paths)

target_link_libraries(${PROJECT_NAME} PRIVATE SDL3::SDL3)

```

which builds SDL3 Hello, World! as emscripten (javascript and WASM files) from the same C++ source file using generator (-G) Ninja

I want to control the entire build from a single CMakeList.txt, so I thought to trigger emscripten build from the end of the C++ build by adding the following to the end of `<project root>CMakeList.txt`

```auto

set(ENV{CMAKE_GENERATOR} Ninja)

add_subdirectory(emscripten)

```

However it fails with errors -

```auto

CMake Error at emscripten/CMakeLists.txt:23 (find_package):

Could not find a configuration file for package "SDL3" that is compatible

with requested version "".

The following configuration files were considered but not accepted:

<project root>emscripten/install_libSDL3/lib/cmake/SDL3/SDL3Config.cmake, version: 3.4.2 (32bit)

The version found is not compatible with the version requested.

```

I also tried adding `add_subdirectory(emscripten)` to the end of `<project root>CMakeList.txt` and building with `cmake - B build -G Ninja`, i.e the same generator for both `CMakeList.txt` files but it gave the same error.

Is there a way I can control the entire build from a main `CMakeList.txt`?

---

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [April 8, 2026, 8:48am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/2 "2026-04-08T08:48:02Z")

</div>

After further research, CMake seems to expect a single build system per invocation. In other words, `add_subdirectory` does not support a different generator, toolchain or compilers from the calling `CMakeLists.txt`. Can anyone confirm this?

---

<div class="post-metadata">

### Author: ![hsattler](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/h/59ef9b/32.png) [@hsattler](https://discourse.cmake.org/u/hsattler)
#### Post date: [April 8, 2026, 6:10pm UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/3 "2026-04-08T18:10:58Z")

</div>

If you want to build with several toolchains, you can use a CMake project that wraps each sub- build as ExternalProject.

---

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [May 28, 2026, 8:25am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/4 "2026-05-28T08:25:13Z")

</div>

> [@hsattler](#):
>
> ExternalProject

I have a working master `CMakeLists.txt`

```auto
cmake_minimum_required(VERSION 3.23)

project(checkers)
add_subdirectory(src)

```

where directory `src` contains my cpp files and their associated `CMakeLists.txt`. I successfully generated the build system with

`cmake -B build -DCMAKE_CXX_COMPILER=clang++ -DSDL_STATIC=ON -DSDL_SHARED=OFF -G "Ninja Multi-Config"`

Now I want adapt the master `CMakeLists.txt` to build external projects

```auto
cmake_minimum_required(VERSION 3.23)

project(checkers)

include(ExternalProject)

ExternalProject_Add(checkers_cpp
SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/src
CMAKE_ARGS -DCMAKE_CXX_COMPILER=clang++; -DSDL_STATIC=ON; -DSDL_SHARED=OFF
CMAKE_GENERATOR "Ninja Multi-Config"
)

```

but received error:

```auto
The current configuration mixes Clang and MSVC or some other CL compatible
    compiler tool. This is not supported. Use either Clang or MSVC as the
    compiler for all of C, C++, and/or HIP.

```

I suspect the error comes from my `CMAKE_ARGS` options. I have tried with and without quotes but it did not help. Can anyone see where I went wrong?

Shane

---

<div class="post-metadata">

### Author: ![jtxa](https://discourse.cmake.org/user_avatar/discourse.cmake.org/jtxa/32/1535_2.png) [@jtxa](https://discourse.cmake.org/u/jtxa)
#### Post date: [May 28, 2026, 8:51am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/5 "2026-05-28T08:51:14Z")

</div>

By default CMake enabled `C` and `CXX`.  
Specify `LANGUAGES CXX` in your `project` call, if you only want to use C++.

---

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [May 28, 2026, 9:40am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/6 "2026-05-28T09:40:13Z")

</div>

> [@jtxa](#):
>
> LANGUAGES

I added the language to the project command -

`project(checkers LANGUAGES CXX)`

but it still fails. See full cmake output below. Any ideas?

```auto
(3.13) PS C:\Users\sss\dev\SDL3\checkers> cmake -B build     
-- Building for: Visual Studio 18 2026
-- Selecting Windows SDK version 10.0.26100.0 to target Windows 10.0.26200.
-- The C compiler identification is MSVC 19.50.35728.0
-- The CXX compiler identification is MSVC 19.50.35728.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: d:/Program Files/Microsoft Visual Studio/18/Community/VC/Tools/MSVC/14.50.35717/bin/Hostx64/x64/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: d:/Program Files/Microsoft Visual Studio/18/Community/VC/Tools/MSVC/14.50.35717/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (2.5s)
-- Generating done (0.0s)
-- Build files have been written to: C:/Users/sss/dev/SDL3/checkers/build
(3.13) PS C:\Users\sss\dev\SDL3\checkers> cmake --build build
MSBuild version 18.4.0+6e61e96ac for .NET Framework

  1>Checking Build System
  Creating directories for 'checkers'
  Building Custom Rule C:/Users/sss/dev/SDL3/checkers/CMakeLists.txt
  No download step for 'checkers'
  No update step for 'checkers'
  No patch step for 'checkers'
  Performing configure step for 'checkers'
  -- The C compiler identification is MSVC 19.50.35728.0
  -- The CXX compiler identification is Clang 22.1.1 with GNU-like command-line
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Check for working C compiler: D:/Program Files/Microsoft Visual Studio/18/Community/VC/Tools/MSVC/14.50.35717/bin/
  Hostx64/x64/cl.exe - skipped
  -- Detecting C compile features
  -- Detecting C compile features - done
  CMake Error at C:/Program Files/CMake/share/cmake-4.3/Modules/Platform/Windows-Clang.cmake:187 (message):
    The current configuration mixes Clang and MSVC or some other CL compatible
    compiler tool. This is not supported. Use either Clang or MSVC as the
    compiler for all of C, C++, and/or HIP.
  Call Stack (most recent call first):
    C:/Program Files/CMake/share/cmake-4.3/Modules/Platform/Windows-Clang.cmake:196 (__verify_same_language_values)
    C:/Program Files/CMake/share/cmake-4.3/Modules/Platform/Windows-Clang-CXX.cmake:1 (include)
    C:/Program Files/CMake/share/cmake-4.3/Modules/CMakeCXXInformation.cmake:48 (include)
    CMakeLists.txt:16 (project)
  
  
  -- Configuring incomplete, errors occurred!
d:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppCommon.targets(254,5): err
or MSB8066: Custom build for 'C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\894992f8c63144c2b6569698e9070c33\checke
rs-mkdir.rule;C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\894992f8c63144c2b6569698e9070c33\checkers-download.rule
;C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\894992f8c63144c2b6569698e9070c33\checkers-update.rule;C:\Users\sss
\dev\SDL3\checkers\build\CMakeFiles\894992f8c63144c2b6569698e9070c33\checkers-patch.rule;C:\Users\sss\dev\SDL3\checke
rs\build\CMakeFiles\894992f8c63144c2b6569698e9070c33\checkers-configure.rule;C:\Users\sss\dev\SDL3\checkers\build\CMa
keFiles\894992f8c63144c2b6569698e9070c33\checkers-build.rule;C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\894992f8
c63144c2b6569698e9070c33\checkers-install.rule;C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\a64faf56fd3aea4aaeca02
d0bd1f2afb\checkers-complete.rule;C:\Users\sss\dev\SDL3\checkers\build\CMakeFiles\8405834ee13b11410e6fbd86de8364be\ch
eckers.rule;C:\Users\sss\dev\SDL3\checkers\CMakeLists.txt' exited with code 1. [C:\Users\sss\dev\SDL3\checkers\buil
d\checkers.vcxproj]

```

---

<div class="post-metadata">

### Author: ![jtxa](https://discourse.cmake.org/user_avatar/discourse.cmake.org/jtxa/32/1535_2.png) [@jtxa](https://discourse.cmake.org/u/jtxa)
#### Post date: [May 28, 2026, 4:26pm UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/7 "2026-05-28T16:26:03Z")

</div>

Your log still says that the C compiler is detected, for your super project and for your external project.

So you maybe have changed the wrong file, maybe you need a fresh configure (simply remove your build directory).

---

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [May 28, 2026, 4:32pm UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/8 "2026-05-28T16:32:51Z")

</div>

In the cmake output above, I did delete the `build` directory before running `cmake -B build` followed by `cmake --build build`

---

<div class="post-metadata">

### Author: ![jtxa](https://discourse.cmake.org/user_avatar/discourse.cmake.org/jtxa/32/1535_2.png) [@jtxa](https://discourse.cmake.org/u/jtxa)
#### Post date: [May 28, 2026, 5:02pm UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/9 "2026-05-28T17:02:35Z")

</div>

Can you add a `--trace` to the `CMAKE_ARGS`, so the log clearly show the commands used.

If it’s really just `CXX` and the C compiler still gets detected, I would consider this a bug of the Visual Studio generator.  
I don’t use VS, so I do not have experience with it, but I can’t find a documented exception to the normal behavior.

---

<div class="post-metadata">

### Author: ![Shane](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/s/dbc845/32.png) [@Shane](https://discourse.cmake.org/u/Shane)
#### Post date: [May 28, 2026, 5:35pm UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/10 "2026-05-28T17:35:44Z")

</div>

I added `--trace` to the master `CMakeLists.txt` -

```auto
cmake_minimum_required(VERSION 3.23)

project(checkers LANGUAGES CXX)

include(ExternalProject)

ExternalProject_Add(checkers_cpp
SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/src
CMAKE_ARGS -DCMAKE_CXX_COMPILER=clang++ --trace; -DSDL_STATIC=ON; -DSDL_SHARED=OFF
CMAKE_GENERATOR "Ninja Multi-Config"
)

```

Trace (too large for [discourse.cmake.org](http://discourse.cmake.org)) : [MSBuild version 18.4.0+6e61e96ac for .NET... - Pastes.io](https://pastes.io/cM9FZ13Q)

---

<div class="post-metadata">

### Author: ![jtxa](https://discourse.cmake.org/user_avatar/discourse.cmake.org/jtxa/32/1535_2.png) [@jtxa](https://discourse.cmake.org/u/jtxa)
#### Post date: [June 5, 2026, 9:10am UTC](https://discourse.cmake.org/t/how-to-include-subdirectory-with-a-different-generator/15594/11 "2026-06-05T09:10:42Z")

</div>

At the very top of your log it reports the project call looks like this:

```plaintext
C:/Users/sss/dev/SDL3/checkers/src/CMakeLists.txt(16): project(checkers_cpp )

```

Please confirm from the command line, what that line really looks like, e.g. `TYPE C:\Users\sss\dev\SDL3\checkers\src\CMakeLists.txt`