Clang not found

[opelx]

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I run into a strange problem:

PS D:\my\cmake-vscode\ibis-conan> cmake --preset windows-clang-release
Preset CMake variables:

  CMAKE_BUILD_TYPE="Release"
  CMAKE_CXX_COMPILER="clang++"
  CMAKE_EXPORT_COMPILE_COMMANDS="ON"
  CMAKE_INSTALL_PREFIX="D:/My/cmake-vscode/ibis-conan/build/windows-clang-release/install"
  MY_CACHE_VAR="empty"

-- The CXX compiler identification is Clang 13.0.0 with GNU-like command-line
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/Llvm/x64/bin/clang++.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- System name: Windows
-- Version: 0.0.1
-- Found Python3: C:/Users/olpetzol/AppData/Local/Programs/Python/Python310/python.exe (found version "3.10.4") found components: Interpreter
-- Downloading conan.cmake from https://github.com/conan-io/cmake-conan
CMake Error at build/windows-clang-release/conan.cmake:233 (message):
  Conan: compiler setup not recognized
Call Stack (most recent call first):
  build/windows-clang-release/conan.cmake:447 (_conan_detect_compiler)
  CMakeLists.txt:100 (conan_cmake_autodetect)


-- Configuring incomplete, errors occurred!
See also "D:/My/cmake-vscode/ibis-conan/build/windows-clang-release/CMakeFiles/CMakeOutput.log".
PS D:\my\cmake-vscode\ibis-conan> clang++.exe --version
clang version 13.0.0
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\Llvm\x64\bin
PS D:\my\cmake-vscode\ibis-conan>

It's using the CLI Clang from VS2020 (not clang-cl). MSVC compiler works as expected, using

cmake_minimum_required(VERSION 3.20)

project(...    LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

list(APPEND
    CMAKE_MODULE_PATH
        ${CMAKE_BINARY_DIR} # conan
        ${PROJECT_SOURCE_DIR}/cmake
        ${PROJECT_SOURCE_DIR}/cmake/module
)

include(prevent_in_source_builds)

find_package(Python3 COMPONENTS Interpreter REQUIRED)

if(NOT EXISTS "${CMAKE_BINARY_DIR}/conan.cmake")
    message(STATUS "Downloading conan.cmake from https://github.com/conan-io/cmake-conan")
    file(DOWNLOAD
        "https://raw.githubusercontent.com/conan-io/cmake-conan/0.18.1/conan.cmake"
        "${CMAKE_BINARY_DIR}/conan.cmake"
        TLS_VERIFY ON)
endif()

include(${CMAKE_BINARY_DIR}/conan.cmake)

conan_cmake_configure(
    REQUIRES
        boost/1.78.0
        cli11/2.2.0
        #fmt/6.1.2
    GENERATORS
        cmake_find_package
        cmake_find_package_multi
        virtualenv
    IMPORTS "bin, *.dll -> ${CMAKE_BINARY_DIR}/bin"
    IMPORTS "lib, *.dylib* -> ${CMAKE_BINARY_DIR}/lib"
    OPTIONS ...
)

conan_cmake_autodetect(conan_settings)
message(STATUS "Conan: Detected settings: ${conan_settings}")

conan_cmake_install(
    PATH_OR_REFERENCE .
    BUILD missing
    REMOTE conancenter
    SETTINGS ${conan_settings}
)

What happended here?

[czoido]

Hi @opelx, Looks like conan_cmake_autodetect is not able to detect the compiler in this case. It works for the most used cases but does not implement every os/compiler combination. I would recommend skipping the conan_cmake_autodetect step for this case and explicitly passing the SETTINGS argument or a PROFILE to conan_cmake_install

[ibis-hdl]

As far I know, it did work before it was changed for MSVC Clang. Anyway, Linux and Clang combination isn't a very exotic OS/compiler combination.

[IceflowRE]

Looks like conan_cmake_autodetect is not able to detect the compiler in this case. It works for the most used cases but does not implement every os/compiler combination. I would recommend skipping the conan_cmake_autodetect step for this case and explicitly passing the SETTINGS argument or a PROFILE to conan_cmake_install

Tried this, but then conan is trying to use "MinGW Makefiles" for the dependencies. Which will fail obviously.

[hwhsu1231]

I think the reason comes from the value of CMAKE_<LANG>_COMPILER_FRONTEND_VARIANT.

• Its value will be GNU if we specify clang.exe/clang++.exe as the compiler.
• Its value will be MSVC if we specify clang-cl.exe as the compiler.

However, it seems that _conan_detect_compiler() only consider the situations using clang-cl.exe:

• https://github.com/conan-io/cmake-conan/blob/0.18.1/conan.cmake#L173-L175
• https://github.com/conan-io/cmake-conan/blob/0.18.1/conan.cmake#L196-L199

I add the following 3 lines in the macro _conan_detect_compiler() to check their values:

message("CMAKE_${LANGUAGE}_COMPILER_ID = ${CMAKE_${LANGUAGE}_COMPILER_ID}")
message("CMAKE_${LANGUAGE}_COMPILER_FRONTEND_VARIANT = ${CMAKE_${LANGUAGE}_COMPILER_FRONTEND_VARIANT}")
message("CMAKE_${LANGUAGE}_SIMULATE_ID = ${CMAKE_${LANGUAGE}_SIMULATE_ID}")

And here are screenshots of the result: