Troubles with C++20 modules and CMake

Troubles with C++20 modules and CMake

[Hlusicka, Jakub (Ceske vysoke uceni technicke v Praze -...)]

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Hello, I am trying to use C++20 modules with CMake and GCC, but I cannot seem to be able to get it to work. I am getting the following error message when running CMake to generate build files:

CMake Error in core/CMakeLists.txt:
  The target named "core" has C++ sources that may use modules, but the
  compiler does not provide a way to discover the import graph dependencies.
  See the cmake-cxxmodules(7) manual for details.  Use the
  CMAKE_CXX_SCAN_FOR_MODULES variable to enable or disable scanning.

The versions of the software I am using:
GCC version: 13.2.1
CMake version: 3.28.3

Is this feature currently not supported, or am I doing something wrong?

Thank you,
Jakub Hlusička


INTERNAL

Re: Troubles with C++20 modules and CMake

[Jonathan Wakely]

On Wed, 21 Feb 2024 at 12:43, Hlusicka, Jakub (Ceske vysoke uceni
technicke v Praze -...) via Gcc-help <gcc-help@gcc.gnu.org> wrote:
>
> Hello, I am trying to use C++20 modules with CMake and GCC, but I cannot seem to be able to get it to work. I am getting the following error message when running CMake to generate build files:
>
> CMake Error in core/CMakeLists.txt:
>   The target named "core" has C++ sources that may use modules, but the
>   compiler does not provide a way to discover the import graph dependencies.
>   See the cmake-cxxmodules(7) manual for details.  Use the
>   CMAKE_CXX_SCAN_FOR_MODULES variable to enable or disable scanning.
>
> The versions of the software I am using:
> GCC version: 13.2.1
> CMake version: 3.28.3
>
> Is this feature currently not supported, or am I doing something wrong?

As it says at https://cmake.org/cmake/help/latest/manual/cmake-cxxmodules.7.html#compiler-support
you need GCC 14 (which won't be released for a few months) to use
CMake's modules support.