class VariantChoice {
// Internal implementation of variant choice
// This partition is not exported here or in primary interface unit
// as it is an implementation detail...
};
```
**CMakeLists.txt** files for `PdSTL` directory is:
**Root/PdSTL/Variant/CMakeLists.txt:**
```auto
cmake_minimum_required(VERSION 3.28)
target_sources(PdSTL PUBLIC FILE_SET pdstl___variant TYPE CXX_MODULES FILES
${CMAKE_CURRENT_SOURCE_DIR}/variant_storage.cppm
${CMAKE_CURRENT_SOURCE_DIR}/variant_choice.cppm)
```
**Root/PdSTL/CMakeLists.txt:**
```auto
cmake_minimum_required(VERSION 3.28)
project(PdSTL CXX)
set(CMAKE_CXX_STANDARD 23)
# Default to C++ extensions being off. Clang's modules support have trouble
# with extensions right now and it is not required for any other compiler
set(CMAKE_CXX_EXTENSIONS OFF)
add_library(PdSTL STATIC "")
add_subdirectory(Variant)
target_sources(PdSTL PUBLIC FILE_SET pd_stl_root TYPE CXX_MODULES FILES
Variant.cppm)
set_target_properties(PdSTL PROPERTIES COMPILE_FLAGS "-g -Wall -Werror -Wextra -Wpedantic -ffreestanding -fno-stack-protector -fno-rtti -fno-exceptions")
target_include_directories(PdSTL PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
```
The content of the Kernel directory is as follows:
**Root/Kernel/BootInfo/BootInfo.cppm:**
```c++
// Root/Kernel/BootInfo/BootInfo.cppm
export module Kernel.BootInfo;
struct BootInfo {
// members of BootInfo
};
```
**Root/Kernel/Graphics/FrameBuffer.cppm:**
```c++
// Root/Kernel/Graphics/FrameBuffer.cppm
export module Kernel.Graphics.FrameBuffer;
struct FrameBuffer {
// members of FrameBuffer
};
```
`CMakeLists.txt` files for `Kernel` directory are as follows:
**Root/Kernel/BootInfo/CMakeLists.txt:**
```auto
// Root/Kernel/BootInfo/CMakeLists.txt
cmake_minimum_required(VERSION 3.28)
target_sources(Kernel PUBLIC FILE_SET kernel_bootinfo TYPE CXX_MODULES FILES
${CMAKE_CURRENT_SOURCE_DIR}/BootInfo.cppm)
target_include_directories(Kernel PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
```
**Root/Kernel/Graphics/CMakeLists.txt:**
```auto
cmake_minimum_required(VERSION 3.28)
target_sources(Kernel PUBLIC FILE_SET kernel_graphics TYPE CXX_MODULES FILES
${CMAKE_CURRENT_SOURCE_DIR}/FrameBuffer.cppm)
target_include_directories(Kernel PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
```
**Root/Kernel/CMakeLists.txt:**
```auto
cmake_minimum_required(VERSION 3.28)
project(Kernel CXX)
set(CMAKE_CXX_STANDARD 23)
# Default to C++ extensions being off. Clang's modules support have trouble
# with extensions right now and it is not required for any other compiler
set(CMAKE_CXX_EXTENSIONS OFF)
add_library(Kernel "")
add_subdirectory(BootInfo)
add_subdirectory(Graphics)
target_link_libraries(Kernel PdSTL)
set_target_properties(Kernel PROPERTIES COMPILE_FLAGS "-g -Wall -Werror -Wextra -Wpedantic -ffreestanding -fno-stack-protector -fno-rtti -fno-exceptions")
target_include_directories(Kernel PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
```
**Root/Kernel.cpp:**
```c++
import Kernel.Graphics.FrameBuffer;
int main() {
// some stuff....
return 0;
}
```
Finally, `CMakeLists.txt` in the `Root` folder looks as follows:
**Root/CMakeLists.txt:**
```auto
cmake_minimum_required(VERSION 3.28)
project(Root)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_EXTENSIONS OFF)
add_executable(Root src/Kernel.cpp)
add_subdirectory(PdSTL)
add_subdirectory(Kernel)
target_link_libraries(Root PdSTL Kernel)
set_target_properties(Root PROPERTIES COMPILE_FLAGS "-g -mcmodel=large -Wall -Werror -Wextra -Wpedantic -ffreestanding -fno-stack-protector -fno-rtti -fno-exceptions -fno-pie -O0")
set_target_properties(Root PROPERTIES LINK_FLAGS "-no-pie -T ${LDS} -static -Bsymbolic -nostdlib")
set_target_properties(Root PROPERTIES OUTPUT_NAME kernel.elf)
```
With this setup, IDE (CLion) ran the following commands to build the executable:
```auto
//When loading CMake project
/usr/bin/cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_MAKE_PROGRAM=/usr/bin/ninja -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -G Ninja -S /home/user/CLionProjects/Root -B /home/user/CLionProjects/Root/cmake-build-debug
```
Project loading runs successfully with the following output:
```auto
-- The C compiler identification is Clang 16.0.6
-- The CXX compiler identification is Clang 16.0.6
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/clang - 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: /usr/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- The ASM compiler identification is Clang with GNU-like command-line
-- Found assembler: /usr/bin/clang
-- Configuring done (0.8s)
-- Generating done (0.0s)
-- Build files have been written to: /home/user/CLionProjects/Root/
[Finished]
```
Pressing the **build** button runs the following command **which fails**
```auto
/usr/bin/cmake --build /home/user/CLionProjects/Root/cmake-build-debug --target Root -j 6
```
```auto
[1/199] Building CXX object CMakeFiles/Root.dir/src/Kernel.cpp.o
FAILED: CMakeFiles/Root.dir/src/Kernel.cpp.o
/usr/bin/clang++ -I/home/user/CLionProjects/Root/PdSTL -I/home/user/CLionProjects/Root/Kernel/ASM -I/home/user/CLionProjects/Root/Kernel/Base -I/home/user/CLionProjects/Root/Kernel/BootInfo -I/home/user/CLionProjects/Root/Kernel/Debug -I/home/user/CLionProjects/Root/Kernel/EFI_Memory -I/home/user/CLionProjects/Root/Kernel/Fonts -I/home/user/CLionProjects/Root/Kernel/Graphics -I/home/user/CLionProjects/Root/Kernel -g -std=c++20 -fcolor-diagnostics -g -mcmodel=large -Wall -Werror -Wextra -Wpedantic -ffreestanding -fno-stack-protector -fno-rtti -fno-exceptions -fno-pie -O0 -MD -MT CMakeFiles/Root.dir/src/Kernel.cpp.o -MF CMakeFiles/Root.dir/src/Kernel.cpp.o.d -o CMakeFiles/Root.dir/src/Kernel.cpp.o -c /home/user/CLionProjects/Root/src/Kernel.cpp
/home/user/CLionProjects/Root/src/Kernel.cpp:1:8: fatal error: module 'Kernel.Graphics' not found
import Kernel.Graphics;
~~~~~~~^~~~~~
1 error generated.
ninja: build stopped: subcommand failed.
```
I’m using `cmake` version `3.28`, `clang++` version `16.0.6` and `ninja` version `1.11.1`.
Thanks in advance for your help,
_Johnny_
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [October 22, 2023, 4:09pm UTC](https://discourse.cmake.org/t/using-c-20-modules-in-a-multiple-directory-project/9239/2 "2023-10-22T16:09:07Z")
Taking notes as I see them:
> [@nitroglyceryne](#):
>
> `export module PdSTL.Variant:VariantStorage;`
If you `export module modname:partition;`, you must `export import :partition;` in the primary unit. Given that you do not, I think you want just `module PdSTL.Variant:VariantStorage;` here (same for `:VariantChoice`).
> [@nitroglyceryne](#):
>
> ```auto
> # Default to C++ extensions being off. Clang's modules support have trouble
> # with extensions right now and it is not required for any other compiler
> set(CMAKE_CXX_EXTENSIONS OFF)
>
> ```
Clang 17 is fine now; it was just Clang 16.
> [@nitroglyceryne](#):
>
> `target_include_directories(Kernel PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})`
Do you also have headers? The directory tree seems truncated. If not, this doesn’t seem useful?
> [@nitroglyceryne](#):
>
> `/home/user/CLionProjects/Root/src/Kernel.cpp:1:8: fatal error: module 'Kernel.Graphics' not found`
I see a `Kernel.Graphics.Framebuffer` module, but not a `Kernel.Graphics` module.
---
### Author:  [@nitroglyceryne](https://discourse.cmake.org/u/nitroglyceryne)
#### Post date: [October 22, 2023, 6:09pm UTC](https://discourse.cmake.org/t/using-c-20-modules-in-a-multiple-directory-project/9239/3 "2023-10-22T18:09:03Z")
> [@ben.boeckel](#):
>
> Taking notes as I see them:
>
> > [@nitroglyceryne](#):
> >
> > `export module PdSTL.Variant:VariantStorage;`
>
> If you `export module modname:partition;`, you must `export import :partition;` in the primary unit. Given that you do not, I think you want just `module PdSTL.Variant:VariantStorage;` here (same for `:VariantChoice`).
You are correct. The idea is that `VariantChoice` and `VariantStorage` shouldn’t be used by any user individually. They are needed for the `Variant` class only.
> [@ben.boeckel](#):
>
> > [@nitroglyceryne](#):
> >
> > ```auto
> > # Default to C++ extensions being off. Clang's modules support have trouble
> > # with extensions right now and it is not required for any other compiler
> > set(CMAKE_CXX_EXTENSIONS OFF)
> >
> > ```
>
> Clang 17 is fine now; it was just Clang 16.
Clang 17 isn’t available in distribution’s repository. If you think the Clang version is the culprit, I can try building Clang 17 locally or check AUR.
> [@ben.boeckel](#):
>
> > [@nitroglyceryne](#):
> >
> > `target_include_directories(Kernel PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})`
>
> Do you also have headers? The directory tree seems truncated. If not, this doesn’t seem useful?
I don’t have any headers. I wasn’t sure if this was needed for discoverability.
> [@ben.boeckel](#):
>
> > [@nitroglyceryne](#):
> >
> > `/home/user/CLionProjects/Root/src/Kernel.cpp:1:8: fatal error: module 'Kernel.Graphics' not found`
>
> I see a `Kernel.Graphics.Framebuffer` module, but not a `Kernel.Graphics` module.
You’re correct. I wrote a wrong name in `main.cpp`.
I implemented changes per your review:
- Changed `export module PdSTL.Variant:VariantStorage` to ` module PdSTL.Variant:VariantStorage`
(Same for `VariantChoice`)
- Removed `target_include_directories()`
- Changed `import Kernel.Graphics` to `import Kernel.Graphics.FrameBuffer`
The error stays the same:
```auto
[1/199] Building CXX object CMakeFiles/Root.dir/src/Kernel.cpp.o
FAILED: CMakeFiles/Root.dir/src/Kernel.cpp.o
/usr/bin/clang++ -I/home/user/CLionProjects/Root/PdSTL -I/home/user/CLionProjects/Root/Kernel/ASM -I/home/user/CLionProjects/Root/Kernel/Base -I/home/user/CLionProjects/Root/Kernel/BootInfo -I/home/user/CLionProjects/Root/Kernel/Debug -I/home/user/CLionProjects/Root/Kernel/EFI_Memory -I/home/user/CLionProjects/Root/Kernel/Fonts -I/home/user/CLionProjects/Root/Kernel/Graphics -I/home/user/CLionProjects/Root/Kernel -g -std=c++20 -fcolor-diagnostics -g -mcmodel=large -Wall -Werror -Wextra -Wpedantic -ffreestanding -fno-stack-protector -fno-rtti -fno-exceptions -fno-pie -O0 -MD -MT CMakeFiles/Root.dir/src/Kernel.cpp.o -MF CMakeFiles/Root.dir/src/Kernel.cpp.o.d -o CMakeFiles/Root.dir/src/Kernel.cpp.o -c /home/user/CLionProjects/Root/src/Kernel.cpp
/home/user/CLionProjects/Root/src/Kernel.cpp:1:8: fatal error: module 'Kernel.Graphics.FrameBuffer' not found
import Kernel.Graphics.FrameBuffer;
~~~~~~~^~~~~~
1 error generated.
ninja: build stopped: subcommand failed.
```
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [October 22, 2023, 7:06pm UTC](https://discourse.cmake.org/t/using-c-20-modules-in-a-multiple-directory-project/9239/4 "2023-10-22T19:06:34Z")
Ok. Without a way to try this myself (remaking all of this out would be tedious and prone to introduce new errors or fix something unintentionally), the places to look (per target):
- `CXXDependInfo.json` files (inter-target dependency information for the collator)
- various `.ddi` files (output of scanning)
- `CXX.dd` files (collator → `ninja` edge additions)
- `CXXModules.json` for CMake-oriented module dependency information
If something seems missing or incorrect in there, that gives the next direction. If everything there looks fine, a Gist with a full tree of this example would be appreciated.
---
### Author:  [@nitroglyceryne](https://discourse.cmake.org/u/nitroglyceryne)
#### Post date: [October 24, 2023, 7:28pm UTC](https://discourse.cmake.org/t/using-c-20-modules-in-a-multiple-directory-project/9239/5 "2023-10-24T19:28:37Z")
Hey, I looked at this again.
I made a pretty silly mistake in my **local** files.
Originally I intended `FrameBuffer` to be a module partition unit of module `Kernel.Graphics`. I wanted to add more partitions later.
In my local files `Root/Kernel/Graphics/FrameBuffer.cppm` had a line
```c++
export module Kernel.Graphics:FrameBuffer;
```
which caused the error.
When I was writing this post I didn’t copy & paste any file for the sake of brevity. I wrote what I believed to be important parts which is why the original post states:
> [@nitroglyceryne](#):
>
> **Root/Kernel/Graphics/FrameBuffer.cppm:**
>
> ```auto
>
> // Root/Kernel/Graphics/FrameBuffer.cppm
>
> export module Kernel.Graphics.FrameBuffer;
>
> struct FrameBuffer {
> // members of FrameBuffer
> };
>
> ```
which isn’t what I had locally.
Thanks for your help