I am trying to install cilk++ according to this website and am at the steps in section "Cilk Plus Runtime". When I go to build, I get the following output:
$ cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_INSTALL_PREFIX=./install ..
CMake Error at CMakeLists.txt:132 (message):
CXX compiler must support Cilk.
-- Configuring incomplete, errors occurred!
See also "/Users/anthonymcknight/Documents/cubing/bfs/lab4/cilk/cilkrts-0.1.2/build/CMakeFiles/CMakeOutput.log".
See also "/Users/anthonymcknight/Documents/cubing/bfs/lab4/cilk/cilkrts-0.1.2/build/CMakeFiles/CMakeError.log".
I thought clang and clang++ (which I checked with --version are indeed installed) would be sufficient. Do I need to update clang and clang++? There are no troubleshooting steps on the instructions website, so I'm not sure what I need to do to finally get cilk++ up and running on my laptop.
Thanks in advance,
Anthony
Expanding on my comment:
When you configure this Cilk Plus Runtime with CMake, CMake first verifies the compiler by attempting to compile a simple test program (see here). If the compilation fails, CMake prints the error you see:
CMake Error at CMakeLists.txt:132 (message):
CXX compiler must support Cilk.
On the Intel Cilk Plus runtime Github page (cilkrts), it has some compiler requirements listed for those trying to build this library:
You need the CMake tool and a C/C++ compiler that supports the Cilk language extensions. The requirements for each operating systems are:
Common: CMake 3.4.3 or later Make tools such as make
Linux: Tapir/LLVM compiler, or GCC* 4.9.2 or later (depracated), or Cilk-enabled branch of Clang*/LLVM* (http://cilkplus.github.io), or Intel(R) C++ Compiler v12.1 or later (depracated)
OS X: Tapir/LLVM compiler, or Cilk-enabled branch of Clang*/LLVM* (http://cilkplus.github.io), or Intel C++ Compiler v12.1 or later (depracated)
Since you are using Clang as your compiler, be sure it is a Cilk-enabled branch of Clang, as specified in the requirements. Or, you can try to use the Tapir/LLVM compiler.
Related
I have a project, which cannot be compiled by a fellow, due to an unknown call to a method from the std library.
I suspect that it's due to the fellow's g++ version (9.4.2) because the function was added in the std 20 standard. To test if that is the case I installed g++-9 (Version 9.5.0) and pointed the /usr/bin/g++ symbolic link to g++-9 and stumbled upon another issue (the question).
When I run
$ g++-9 -std=c++20
g++-9: error: unrecognized command line option ‘-std=20’; did you mean ‘-std=c2x’?
g++-9: fatal error: no input files
compilation terminated.
I get an error stating, that the std standard version 20 is unknown.
But when I try to generate the build files for an cmake project with the following line in the CMakeLists.txt:
target_compile_features(${PROJECT_NAME}
PUBLIC
cxx_std_20
)
I get no error. But when replacing the 20 with a 23:
target_compile_features(${PROJECT_NAME}
PUBLIC
cxx_std_23
)
I get the error
CMake Error at CMakeLists.txt:74 (target_compile_features):
target_compile_features The compiler feature "cxx_std_23" is not known to
CXX compiler
"GNU"
version 9.5.0.
Why is the C++20 standard unknown to g++, but known, when generating build files with cmake?
This is some sort of follow up Question:
When I try to compile my project I get the error:
error: ‘std::stringstream’ {aka ‘class std::__cxx11::basic_stringstream<char>’} has no member named ‘view’
and view was added in c++20. Can it be, that view was jet not added in c++2a?
Well... if your compiler is GCC 9.5.0, the reason why CMake says it doesn't know about C++23 is because... it doesn't?
https://en.cppreference.com/w/cpp/compiler_support
The only thing that cppreference.com's compiler support table says that GCC v9 "knows" about C++23 is "Narrowing contextual conversions in static_assert and constexpr if"
And the reason why you get "g++-9: error: unrecognized command line option ‘-std=20’; did you mean ‘-std=c2x’?" for GCC 9.5.0 is probably just because C++20 support wasn't fully implemented yet. Again, look at the compiler support table in cppreference.com. There are lots of core language features and library features for C++20 that GCC didn't implement until version 10 (some even in version 9-13 Ex. "Atomic Compare-And-Exchange with padding bits")
So just do what it told you to do and take what you get, accepting that not all of the C++20 features will be available in GCC 9.5.0.
Or upgrade you compiler :P
The reason why it works with CMake's target_compile_features(... cxx_std_20) is because... CMake handles it.
See Modules/Compiler/GNU-C.cmake:
if(CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 9.1)
set(CMAKE_C23_STANDARD_COMPILE_OPTION "-std=c2x")
set(CMAKE_C23_EXTENSION_COMPILE_OPTION "-std=gnu2x")
endif()
and Modules/Compiler/GNU-CXX.cmake:
elseif(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 8.0)
set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std=c++2a")
set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std=gnu++2a")
endif()
The name of the option for standard C++20 up to GCC 9 is -std=c++2a. According to man gcc:
c++2a
The next revision of the ISO C++ standard, planned for 2020. Support is highly experimental, and will almost certainly change in incompatible ways in future releases.
So not all features can be expected to be in there.
GCC has a tradition of providing aliases for the not yet released standards or those with incomplete support. GCC 9 only knows c++2a and that became an alias for c++20 with GCC 10.
CMake can handle this. When in doubt what CMake uses as standard (or any other option), take a look in the build directory in flags.make or build.ninja (depending on which generator you're using).
The good news, I was able to compile and install Clang and lld from branch llvmorg-12.0.1 under Windows / Cygwin.
It compiles my code fine but linker says:
lld: error: unknown argument: --dll-search-prefix=cyg
I am wondering because of I thought lld takes the same cli parameters as ld.
I am working on a project which includes gtest and uses the cmake framework. The files for testing are linked as library and later again the tests and finally again gtest.
The code is linking and working when using ggc 11.2.0
--dll-search-prefix is a win32-specific option of ld which is not (yet) implemented in lld.
I am running clang-tidy checks using cmake version 3.20.0-rc1 on Windows 10.
My project builds using GNU 8.3.0.
Sadly I get the error
error: 'cstddef' file not found [clang-diagnostic-error]
#include <cstddef>
clang-tidy info:
LLVM (http://llvm.org/):
LLVM version 12.0.0
Optimized build.
Default target: i686-pc-windows-msvc
Host CPU: skylake
[clang-diagnostic-error] is basically a compiler error coming from the clang backend.
Clang-tidy needs an AST (abstract syntax tree) - your code has to be compileable by clang compiler in order to generate an AST. Only then will clang-tidy analyze your code.
Get your code to compile by clang instead of GCC and you should find the source of your problem.
I am try to build lld from LLVM version 11 (I can't use any later or master version of LLVM for the time-being) and am currently configuring with cmake ~/Downloads/lld-11.0.0.src/ -DCMAKE_INSTALL_PREFIX=$HOME/bin/llvm -DCMAKE_PREFIX_PATH=$HOME/bin/llvm -DCMAKE_BUILD_TYPE=Release -G Ninja but ninja install then fails with 20 errors that I think are all standard library related (such as "unknown type name 'constexpr'" and "no template named 'underlying_type_t' in namespace 'std'; did you mean 'underlying_type'?").
The compiler cmake is using by default is Apple Clang 12 which came with my system (or was installed automatically). What other flags should I pass to cmake to get this working? Or do I need to use a different compiler? LLVM 11 configures and builds fine with the same cmake flags.
For anyone else experiencing similar issues: Building LLVM, lld and clang from the monorepo all in one go worked. I had to add -DLLVM_ENABLE_PROJECTS="clang;lld" to the cmake command.
I need the freshest CMake installed on my OpenSuse in order to use an app. I'm trying to download it from the official site and follow the instructions: https://cmake.org/install/
However, I get the following errors:
aleksandr#linux-b0ak:~/Downloads/cmake-3.17.0-rc1> cmake .
-- The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:7 (project):
No CMAKE_CXX_COMPILER could be found.
Tell CMake where to find the compiler by setting either the environment
variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
to the compiler, or to the compiler name if it is in the PATH.
-- Configuring incomplete, errors occurred!
See also "/home/aleksandr/Downloads/cmake-3.17.0-rc1/CMakeFiles/CMakeOutput.log".
See also "/home/aleksandr/Downloads/cmake-3.17.0-rc1/CMakeFiles/CMakeError.log".
aleksandr#linux-b0ak:~/Downloads/cmake-3.17.0-rc1> ./bootstrap
---------------------------------------------
CMake 3.17.0-rc1, Copyright 2000-2020 Kitware, Inc. and Contributors
C compiler on this system is: cc
---------------------------------------------
Error when bootstrapping CMake:
Cannot find a C++ compiler that supports both C++11 and the specified C++ flags.
Please specify one using environment variable CXX.
The C++ flags are "".
They can be changed using the environment variable CXXFLAGS.
See cmake_bootstrap.log for compilers attempted.
---------------------------------------------
Log of errors: /home/aleksandr/Downloads/cmake-3.17.0-rc1/Bootstrap.cmk/cmake_bootstrap.log