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 --fresh --trace-expand --trace-source=CMakeDetermineCompilerId.cmake
but use your right path to the your tools!
Here you go, CMake 4.0.3 and clang 21 compiled from source with bin folder on PATH.
I’m on Windows 10 and the Powershell is used in the log
log.txt (163.4 KB)
@ben.boeckel Is this a cmake or a toolchain problem?
CMAKE-STDLIB-DETECT: UNKNOWN
ping @ben.boeckel
This is a different issue, haven’t had time to investigate
who is the packager now?
mccakit is the packager, but again this is a totally unrelated issue from the problem homebrew and nix have.
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I believe there isn’t any std module detection stuff for clang in windows, regardless of toolchain because none of the other toolchains work, ndk,emcc,icx,clang-cl etc
Currently only cl.exe works with std library modules.
Yep, fairly certain that’s correct.
Enabling P3286 metadata detection and usage, at least for clang, on Windows is on the todo list.
clang-cl is a different ballgame as it doesn’t have a single coherent story for how modules work at all right now, much less import std
Good to know I wasn’t crazy. Hope it merges soon!