Currently, import std doesn’t work on Windows. It fails both in a pure Visual Studio environment (using the CMake and Clang provided by Visual Studio) and with the latest versions of LLVM and CMake built from source. I’ve opened an issue about this, but it seems to be ignored—similar problems were r…

[image] Claus Klein: CMake needs the full path to the json file! Check it🙋♂️

[image] Claus Klein: And check the result of CXX=clang++-20 cmake -G Ninja -S . -B build --fresh --trace-expand --trace-source=Clang-CXX-CXXImportStd.cmake Dit you?:face_with_open_eyes_and_hand_over_mouth:

[image] Claus Klein: CXX=clang++-20 cmake -G Ninja -S . -B build --fresh --trace-expand --trace-source=Clang-CXX-CXXImportStd.cmake I did, and by removing CMAKE_CXX_COMPILER and setting the path, like you asked PS C:\Users\cakit\Desktop\std> $env:CXX = "clang++" PS C:\Users\cakit\Desktop\std>…

so read No SOURCES given to target: __CMAKE__CXX26 on ubuntu 25.04 - #10 by ben.boeckel No SOURCES given to target: __CMAKE__CXX26 on ubuntu 25.04 - #12 by ClausKlein

Setting enviroment variables CXX and CXXFLAGS doesn’t solve my issue, here is the log. log.txt (163.4 KB)

so it seems, your toolchain does not support import std or is wrong installed! Do you find libc++.modules.json or libstdc++.modules.json in C:\dev\toolchains\llvm tree?

I do have libc++.modules.json in C:\dev\toolchains\llvm\lib\libc++.modules.json

please see No SOURCES given to target: __CMAKE__CXX26 on ubuntu 25.04 - #11 by ClausKlein you may trace CMakeDetermineComilerId.cmake while configure oder compile the file yourself.

Nope, this is enough. We have gone full circle. It is the developers job to deal with this.

5 sec before the destination you give it up? We need the output of: /usr/local/Cellar/llvm/20.1.6/bin/clang++ -stdlib=libc++ -E -x c++-header /Users/clausklein/.local/share/cmake-4.0/Modules/CXX-DetectStdlib.h or CXX=clang++ CXXFLAGS=-stdlib=libc++ ~/.local/bin/cmake -G Ninja -S . -B build --fr…

``import std`` doesn't work on windows

Usage

ClausKlein (Claus Klein) July 9, 2025, 4:28pm 29