Since the support is now stable (https://www.kitware.com/import-cmake-the-experiment-is-over/ ), I tried out C++ modules using cmake and clang 18.
However, compiling the source gave me:
The target named "<target>" 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.
clang --version:
Debian clang version 18.0.0 (++20240101112328+703e83611cd8-1~exp1~20240101112345.435)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
cmake --version:
cmake version 3.28.1
CMake suite maintained and supported by Kitware (kitware.com/cmake).
CMakeLists.txt:
add_library(lib STATIC)
target_sources(lib
PUBLIC
FILE_SET CXX_MODULES FILES
file.ccm
)
Any pointers?
ben.boeckel
January 2, 2024, 1:04pm
2
Do you have a clang-scan-deps binary around?
In fact I did not, but even if I install it, that makes no difference.
$ clang-scan-deps --version
clang-scan-deps
Debian LLVM version 18.0.0
Optimized build.
But thanks for the effort.
ben.boeckel
January 2, 2024, 1:45pm
4
Hmm. That is odd. Debian stable or testing? I’ll try it out in a container here.
1 Like
standard debian from WSL
$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 12 (bookworm)
Release: 12
Codename: bookworm
$ uname -a
Linux NAME 5.15.133.1-microsoft-standard-WSL2 #1 SMP Thu Oct 5 21:02:42 UTC 2023 x86_64 GNU/Linux
$ ls -lsa /usr/bin/ | grep clang
0 lrwxrwxrwx 1 root root 24 Jul 27 13:38 clang -> ../lib/llvm-18/bin/clang
0 lrwxrwxrwx 1 root root 26 Jul 27 13:38 clang++ -> ../lib/llvm-18/bin/clang++
0 lrwxrwxrwx 1 root root 26 Feb 17 2023 clang++-14 -> ../lib/llvm-14/bin/clang++
0 lrwxrwxrwx 1 root root 24 Feb 17 2023 clang-14 -> ../lib/llvm-14/bin/clang
0 lrwxrwxrwx 1 root root 26 Jan 1 12:23 clang++-18 -> ../lib/llvm-18/bin/clang++
0 lrwxrwxrwx 1 root root 24 Jan 1 12:23 clang-18 -> ../lib/llvm-18/bin/clang
0 lrwxrwxrwx 1 root root 43 Jan 1 12:23 clang-apply-replacements-18 -> ../lib/llvm-18/bin/clang-apply-replacements
0 lrwxrwxrwx 1 root root 41 Jan 1 12:23 clang-change-namespace-18 -> ../lib/llvm-18/bin/clang-change-namespace
0 lrwxrwxrwx 1 root root 30 Jan 1 12:23 clang-check-18 -> ../lib/llvm-18/bin/clang-check
0 lrwxrwxrwx 1 root root 27 Jan 1 12:23 clang-cl-18 -> ../lib/llvm-18/bin/clang-cl
0 lrwxrwxrwx 1 root root 28 Feb 17 2023 clang-cpp-14 -> ../lib/llvm-14/bin/clang-cpp
0 lrwxrwxrwx 1 root root 28 Jan 1 12:23 clang-cpp-18 -> ../lib/llvm-18/bin/clang-cpp
0 lrwxrwxrwx 1 root root 25 Dec 8 09:59 clangd-17 -> ../lib/llvm-17/bin/clangd
0 lrwxrwxrwx 1 root root 28 Jan 1 12:23 clang-doc-18 -> ../lib/llvm-18/bin/clang-doc
0 lrwxrwxrwx 1 root root 39 Jan 1 12:23 clang-extdef-mapping-18 -> ../lib/llvm-18/bin/clang-extdef-mapping
0 lrwxrwxrwx 1 root root 15 Jul 27 13:38 clang-format -> clang-format-18
0 lrwxrwxrwx 1 root root 31 Jan 1 12:23 clang-format-18 -> ../lib/llvm-18/bin/clang-format
0 lrwxrwxrwx 1 root root 20 Jul 27 13:38 clang-format-diff -> clang-format-diff-18
8 -rwxr-xr-x 1 root root 6273 Jan 1 12:23 clang-format-diff-18
0 lrwxrwxrwx 1 root root 40 Jan 1 12:23 clang-include-cleaner-18 -> ../lib/llvm-18/bin/clang-include-cleaner
0 lrwxrwxrwx 1 root root 38 Jan 1 12:23 clang-include-fixer-18 -> ../lib/llvm-18/bin/clang-include-fixer
0 lrwxrwxrwx 1 root root 39 Jan 1 12:23 clang-linker-wrapper-18 -> ../lib/llvm-18/bin/clang-linker-wrapper
0 lrwxrwxrwx 1 root root 29 Jan 1 12:23 clang-move-18 -> ../lib/llvm-18/bin/clang-move
0 lrwxrwxrwx 1 root root 40 Jan 1 12:23 clang-offload-bundler-18 -> ../lib/llvm-18/bin/clang-offload-bundler
0 lrwxrwxrwx 1 root root 41 Jan 1 12:23 clang-offload-packager-18 -> ../lib/llvm-18/bin/clang-offload-packager
0 lrwxrwxrwx 1 root root 31 Jan 1 12:23 clang-pseudo-18 -> ../lib/llvm-18/bin/clang-pseudo
0 lrwxrwxrwx 1 root root 30 Jan 1 12:23 clang-query-18 -> ../lib/llvm-18/bin/clang-query
0 lrwxrwxrwx 1 root root 33 Jan 1 12:23 clang-refactor-18 -> ../lib/llvm-18/bin/clang-refactor
0 lrwxrwxrwx 1 root root 31 Jan 1 12:23 clang-rename-18 -> ../lib/llvm-18/bin/clang-rename
0 lrwxrwxrwx 1 root root 39 Jan 1 12:23 clang-reorder-fields-18 -> ../lib/llvm-18/bin/clang-reorder-fields
0 lrwxrwxrwx 1 root root 29 Jan 1 12:23 clang-repl-18 -> ../lib/llvm-18/bin/clang-repl
0 lrwxrwxrwx 1 root root 27 Jan 2 14:34 clang-scan-deps -> /usr/bin/clang-scan-deps-18
0 lrwxrwxrwx 1 root root 34 Jan 1 12:23 clang-scan-deps-18 -> ../lib/llvm-18/bin/clang-scan-deps
0 lrwxrwxrwx 1 root root 31 Jan 1 12:23 clang-tblgen-18 -> ../lib/llvm-18/bin/clang-tblgen
0 lrwxrwxrwx 1 root root 19 Jul 27 13:38 git-clang-format -> git-clang-format-18
0 lrwxrwxrwx 1 root root 35 Jan 1 12:23 git-clang-format-18 -> ../lib/llvm-18/bin/git-clang-format
0 lrwxrwxrwx 1 root root 48 Jan 1 12:23 hwasan_symbolize-18 -> ../lib/llvm-18/lib/clang/18/bin/hwasan_symbolize
0 lrwxrwxrwx 1 root root 43 Jan 1 12:23 scan-build-18 -> ../share/clang/scan-build-18/bin/scan-build
0 lrwxrwxrwx 1 root root 41 Jan 1 12:23 scan-view-18 -> ../share/clang/scan-view-18/bin/scan-view
complete minimal example(same environment):
cmake_minimum_required(VERSION 3.28)
project(PACtrl LANGUAGES CXX)
add_library(test STATIC)
target_sources(test
PUBLIC
FILE_SET CXX_MODULES FILES
test.ccm
)
set_property(TARGET test PROPERTY CXX_STANDARD 20)
set_property(TARGET test PROPERTY CXX_STANDARD_REQUIRED ON)
set_property(TARGET test PROPERTY CXX_EXTENSIONS OFF)
module;
export module test;
namespace test {
int i(void)
{
return 1;
}
}
$ cmake . build -GNinja
CMake Warning:
Ignoring extra path from command line:
"build"
-- Configuring done (0.0s)
CMake Error in CMakeLists.txt:
The target named "test" 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.
-- Generating done (0.0s)
CMake Generate step failed. Build files cannot be regenerated correctly.
ben.boeckel
January 2, 2024, 2:39pm
7
CMake’s test suite ran fine:
$ apt install clang-tools-18
$ CC=clang-18 CXX=clang++-18 ../cmake-3.28.1-linux-x86_64/bin/cmake -GNinja ../src -DCMake_TEST_HOST_CMAKE=1 -DCMake_TEST_MODULE_COMPILATION=named,compile_commands,collation,partitions,internal_partitions,export_bmi,install_bmi,shared,bmionly
$ ninja
$ CC=clang-18 CXX=clang++-18 ../cmake-3.28.1-linux-x86_64/bin/ctest -R CXXModules
ben.boeckel
January 2, 2024, 2:39pm
8
Are you sure CMake is trying to use Clang and not GCC here?
Thanks, that was the issue. Somehow, GCC and clang got messed up.
ben.boeckel
January 2, 2024, 4:02pm
10
CMake defaults to searching for cc and c++ which are (generally) GCC on Linux distros. If that doesn’t exist, GCC is searched for first.
1 Like