I'm trying to compile a Git project, and I'm facing some problems with CMake. Initially, it didn't find the C++ compiler and prompted an error:
cmake ..
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.
So, I did:
CXX="gcc" cmake ..
But another error was prompted:
-- The CXX compiler identification is unknown
-- Check for working CXX compiler: /usr/bin/gcc
-- Check for working CXX compiler: /usr/bin/gcc -- broken
CMake Error at /usr/share/cmake-3.0/Modules/CMakeTestCXXCompiler.cmake:54 (message):
The C++ compiler "/usr/bin/gcc" is not able to compile a simple test program.
How can I solve this error and compile the project?
You should try installing build-essential if you haven't done so.
Try this
sudo apt-get update
sudo apt-get install -y build-essential
You are trying to use C compiler gcc as C++ one, which is wrong.
You need to install g++ or other C++ compiler.
Related
In order to make use of newer C++ 17 and 20 features, I want to switch from Apple clang to a homebrew installed vanilla clang. I installed it via brew install llvm.
When trying to build a minimal CMake based test project like
cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_COMPILER=/usr/local/opt/llvm/bin/clang -DCMAKE_CXX_COMPILER=/usr/local/opt/llvm/bin/clang++ -G Ninja testProject
CMake fails with
-- The C compiler identification is Clang 13.0.0
-- The CXX compiler identification is Clang 13.0.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - failed
-- Check for working C compiler: /usr/local/opt/llvm/bin/clang
-- Check for working C compiler: /usr/local/opt/llvm/bin/clang - broken
CMake Error at /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.20/Modules/CMakeTestCCompiler.cmake:66 (message):
The C compiler
"/usr/local/opt/llvm/bin/clang"
is not able to compile a simple test program.
It fails with the following output:
Change Dir: /Users/me/Projects/testProject/build/CLion/Debug/CMakeFiles/CMakeTmp
Run Build Command(s):/usr/local/bin/ninja cmTC_d2d4b && [1/2] Building C object CMakeFiles/cmTC_d2d4b.dir/testCCompiler.c.o
[2/2] Linking C executable cmTC_d2d4b
FAILED: cmTC_d2d4b
: && /usr/local/opt/llvm/bin/clang -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names CMakeFiles/cmTC_d2d4b.dir/testCCompiler.c.o -o cmTC_d2d4b && :
ld: library not found for -lSystem
clang-13: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
So it seems that it fails to locate the correct library search path out of the box.
When trying to build a simple hello world program from the command line like
/usr/local/opt/llvm/bin/clang++ main.cpp -isysroot /Library/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk
It fails with even not finding some headers.
Supplying the header and library search path explicitly to the build command like
/usr/local/opt/llvm/bin/clang++ main.cpp -I"/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include" -L"/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib"
makes it work. However, both are no solutions to make the built-in CMake compiler check work and they don't seem like the correct way to go.
Once this is working correctly, I'm furthermore interested in being able to compile ObjectiveC++ code which currently fails with even more errors.
I think I understand the problem that the compiler does not know the correct search paths, but I'm lacking some understanding about how it would normally figure out those search paths in a CMake project.
I finally managed to get it working by supplying a few linker flags through the LDFLAGS environment variable:
-L/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk/usr/lib
In order to find the system libraries needed by the C compiler check
-L/usr/local/opt/llvm/lib
In order to find the C++ libraries as needed by the C++ compiler check
In order to successfully compile Objective-C code that links to Apple frameworks, I furthermore needed to add
-F/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk/System/Library/Frameworks -lobjc
With those flags, I now can successfully build my projects. Still, I'm not 100% sure if this is the right way, especially if the libraries linked from /usr/local/opt/llvm/lib can be expected to be present on all target systems?
I am trying to build this project, which has CUDA as a dependency. But the cmake script cannot find the CUDA installation on the system:
cls ~/workspace/gpucluster/cluster/build $ cmake ..
-- The C compiler identification is GNU 4.7.1
-- The CXX compiler identification is GNU 4.7.1
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
CMake Error at /usr/share/cmake/Modules/FindCUDA.cmake:488 (message):
Specify CUDA_TOOLKIT_ROOT_DIR
Call Stack (most recent call first):
CMakeLists.txt:20 (find_package)
-- Configuring incomplete, errors occurred!
I've tried adding it as an environment variable to .bashrc, to no effect:
export CUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda-5.5
How do I Specify CUDA_TOOLKIT_ROOT_DIR correctly?
cmake mentioned CUDA_TOOLKIT_ROOT_DIR as cmake variable, not environment one. That's why it does not work when you put it into .bashrc. If you look into FindCUDA.cmake it clearly says that:
The script will prompt the user to specify CUDA_TOOLKIT_ROOT_DIR if the prefix
cannot be determined by the location of nvcc in the system path and REQUIRED
is specified to find_package(). To use a different installed version of the
toolkit set the environment variable CUDA_BIN_PATH before running cmake
(e.g. CUDA_BIN_PATH=/usr/local/cuda1.0 instead of the default /usr/local/cuda)
or set CUDA_TOOLKIT_ROOT_DIR after configuring. If you change the value of
CUDA_TOOLKIT_ROOT_DIR, various components that depend on the path will be
relocated.
So put CUDA_BIN_PATH into .bashrc or specify CUDA_TOOLKIT_ROOT_DIR to cmake:
cmake -D CUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda-5.5 ..
FindCMake.cmake looks for /usr/local/cuda. In your case, that directory might not be there. Just create a symbolic link of that name to your actual CUDA installation directory:
$ sudo ln -s /usr/local/cuda-5.5 /usr/local/cuda
Your CMake should be able to generate the Makefile for your project now.
Maybe CUDA was installed from sources (and nvcc is not in the path). Then the script can not set CUDA_TOOLKIT_ROOT_DIR because of nvcc missing. For me it worked fine after running:
sudo apt install nvidia-cuda-toolkit
(This package might require several GiB of space)
Since CMake 3.8, FindCUDA is deprecated and the proper way of using CUDA in CMake projects is enabling it via project() or enable_language()
https://cmake.org/cmake/help/v3.8/release/3.8.html#cuda
In terminal, type nano ~/.bashrc. Then add the following lines to the file:
export PATH=$PATH:/usr/local/cuda/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda/lib:/usr/local/lib
export CPLUS_INCLUDE_PATH=/usr/local/cuda/include
Save the file, then type source ~/.bashrc in terminal.
You may validate if CUDA path has been setup by typing nvcc --version in terminal.
In my case I had to make /usr/lib/cuda point to an actual CUDA installation. So I did:
ln -s /usr/lib/cuda /home/nvidia_libraries/cuda_10.2
I had cuda_10.2 installed locally in my home folder instead of system wide.
I'm new to building in Windows. I'm building the following project: https://github.com/arkottke/strata.
The page suggests installing dependencies using MSYS2. I've installed MSYS2 and installed everything as instructed exactly, but I get the following when trying to build using cmake:
$ cmake .. -DCMAKE_BUILD_TYPE=Release
-- The C compiler identification is unknown
-- The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:31 (project):
No CMAKE_C_COMPILER could be found.
Tell CMake where to find the compiler by setting either the environment
variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to
the compiler, or to the compiler name if it is in the PATH.
CMake Error at CMakeLists.txt:31 (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/isb17182/strata/build/CMakeFiles/CMakeOutput.log".
See also "/home/isb17182/strata/build/CMakeFiles/CMakeError.log".
I've seen answers for the same problem on other building platforms, but these are too complicated for me to understand currently. If someone could provide a simple explanation of how to resolve this it would be much appreciated.
Thanks
This is what worked for me
Thanks to everyone who contributed.
Run
pacman -S base-devel gcc
Which will update GCC to latest and verify by
gcc --version
Be sure you're using the cmake of msys2 (as the project build instructions suggest you should install), not a regular Windows cmake installed elsewhere on the system.
which cmake
After this ere execute your command...build done ;)
I'm having the following problem when trying to build a project using CMake:
-- The C compiler identification is unknown
-- The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:2 (project):
I'm executing the following command: cmake . inside the CMake project folder.
The error also states that I shoulkd try to set the CMAKE_C_COMPILER and CMAKE_CXX_COMPILER enviroment variables to the compiler paths. And so did I.
I've set the variables to the following paths, respectively: C:\MinGW\bin\gcc.exe and C:\MinGW\bin\g++.exe.
The error kept happening.
My CMakeLists looks like this:
cmake_minimum_required(VERSION 2.8.9)
project (hello)
add_executable(hello helloworld.cpp)
I have no CMake knowledge at all so consider that it is possible that I've forgotten some basic stuff.
What am I missing?
I found out what I was doing wrong.
I was not choosing the correct generator, and the following fixed it:
cmake -G "MinGW Makefiles" ..
After selecting MinGW generator, everything worked just fine.
I have a problem with this CMakeLists.txt file:
cmake_minimum_required(VERSION 2.6)
SET(CMAKE_C_COMPILER C:/MinGW/bin/gcc)
SET(CMAKE_CXX_COMPILER C:/MinGW/bin/g++)
project(cmake_test)
add_executable(a.exe test.cpp)
Calling cmake with: cmake -G "MinGW Makefiles" , it fails with the following output:
c:\Users\pietro.mele\projects\tests\buildSystem_test\cmake_test>cmake -G "MinGW Makefiles" .
-- The C compiler identification is GNU 4.6.1
-- The CXX compiler identification is GNU 4.6.1
-- Check for working C compiler: C:/MinGW/bin/gcc
CMake Error: your C compiler: "C:/MinGW/bin/gcc" was not found. Please set CMAKE_C_COMPILER to a valid compiler path or name.
CMake Error: Internal CMake error, TryCompile configure of cmake failed
-- Check for working C compiler: C:/MinGW/bin/gcc -- broken
CMake Error at C:/Program Files (x86)/CMake 2.8/share/cmake-2.8/Modules/CMakeTestCCompiler.cmake:52 (MESSAGE):
The C compiler "C:/MinGW/bin/gcc" is not able to compile a simple test
program.
CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt:10 (project)
CMake Error: your C compiler: "C:/MinGW/bin/gcc" was not found. Please set CMAKE_C_COMPILER to a valid compiler path or name.
CMake Error: your CXX compiler: "C:/MinGW/bin/g++" was not found. Please set CMAKE_CXX_COMPILER to a valid compiler path or name.
-- Configuring incomplete, errors occurred!
However the gcc compiler is in C:/MinGW/bin/ and it works.
Any idea?
Platform:
Windows 7
MinGW/GCC 4.6
Never try to set the compiler in the CMakeLists.txt file.
See the CMake FAQ about how to use a different compiler:
https://gitlab.kitware.com/cmake/community/wikis/FAQ#how-do-i-use-a-different-compiler
(Note that you are attempting method #3 and the FAQ says "(avoid)"...)
We recommend avoiding the "in the CMakeLists" technique because there are problems with it when a different compiler was used for a first configure, and then the CMakeLists file changes to try setting a different compiler... And because the intent of a CMakeLists file should be to work with multiple compilers, according to the preference of the developer running CMake.
The best method is to set the environment variables CC and CXX before calling CMake for the very first time in a build tree.
After CMake detects what compilers to use, it saves them in the CMakeCache.txt file so that it can still generate proper build systems even if those variables disappear from the environment...
If you ever need to change compilers, you need to start with a fresh build tree.
I had similar problem as Pietro,
I am on Window 10 and using "Git Bash".
I tried to execute >>cmake -G "MinGW Makefiles", but I got the same error as Pietro.
Then, I tried >>cmake -G "MSYS Makefiles", but realized that I need to set my environment correctly.
Make sure set a path to C:\MinGW\msys\1.0\bin and check if you have gcc.exe there. If gcc.exe is not there then you have to run C:/MinGW/bin/mingw-get.exe and install gcc from MSYS.
After that it works fine for me
Using with FILEPATH option might work:
set(CMAKE_CXX_COMPILER:FILEPATH C:/MinGW/bin/gcc.exe)
I had the same issue. And in my case the fix was pretty simple. The trick is to simply add the ".exe" to your compilers path. So, instead of :
SET(CMAKE_C_COMPILER C:/MinGW/bin/gcc)
It should be
SET(CMAKE_C_COMPILER C:/MinGW/bin/gcc.exe)
The same applies for g++.