Is it possible to use import std; with CMake?

[Jaakkko]

I'm using

• Android NDK 28.0.12674087
• CMake 3.31.2

According to cmake-cxxmodules import std can be used if Clang 18.1.2 or newer with -stdlib=libc++ is used. And if I'm understanding the NDK documentation correctly libc++ should be enabled by default. I'm meeting all these requirements (Clang version is 19.0.0).

However, I'm getting this error:

CMake Error in CMakeLists.txt:
  The "CXX_MODULE_STD" property on the target "myapplication" requires that
   the "__CMAKE::CXX23" target exist, but it was not provided by the
   toolchain.  Reason:
     Only `libc++` is supported

My CMakeLists.txt looks like this:

cmake_minimum_required(VERSION 3.31.2 FATAL_ERROR)

set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")

project("myapplication" LANGUAGES CXX)

set(CMAKE_CXX_MODULE_STD ON)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS ON)

add_library(${CMAKE_PROJECT_NAME} SHARED myapplication.cpp)

target_link_libraries(${CMAKE_PROJECT_NAME} android log)

Is the import std feature supported? If yes, what am I doing wrong?

[DanAlbert]

(Clang version is 19.0.0).

Not actually. It's an in-development snapshot of LLVM 19 (there's a file in the compiler directory called AndroidVersion.txt or something like that which explains the details). It may be older than 18.1.2. Without knowing which specific LLVM changes CMake needs (I'd be very shocked if anyone knows, that'd be a lot of unnecessary work on their part), the answer is probably "wait for NDK r29". If it doesn't work in r29, file a bug with a repro case. Not really sure if this is a bug or a feature request, but we can start it as a bug and recategorize if needed.