cmake error on Arch Linux

[NanXiao]

Hi,

Greeting from me!

My OS is Arch Linux, and cmake version is 3.14.1. Running "cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_BUILD_TYPE=Release" will generate following error:

# cmake -G Ninja ../llvm -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_BUILD_TYPE=Release
CMake Deprecation Warning at CMakeLists.txt:14 (cmake_policy):
  The OLD behavior for policy CMP0051 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.


CMake Error: CMake was unable to find a build program corresponding to "Ninja".  CMAKE_MAKE_PROGRAM is not set.  You probably need to select a different build tool.
CMake Error: CMAKE_C_COMPILER not set, after EnableLanguage
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
CMake Error: CMAKE_ASM_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!
See also "/root/project/build/CMakeFiles/CMakeOutput.log".

Could you help to check it? Thanks very much in advance!

Best Regards
Nan Xiao

[rafaelauler]

I've seen this error happening with me before when trying to build LLVM in a misconfigured environment, but I don't quite remember what I did. I'm going to guess that the fact that you are missing "ninja" is confusing CMake, so I would first try to install "ninja" before specifying you want to use ninja with "-G Ninja".

So you should either install ninja or drop the "-G Ninja" option and build with make, like this:

cmake ../llvm -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_BUILD_TYPE=Release
make

I don't know the package in Arch that installs ninja, but in Ubuntu it is "ninja-build". So I would try to install ninja or ninja-build, whatever works.

[NanXiao]

@rafaelauler

Yes, this is the problem. Thanks very much for your help!