CMake panics because is "unable to detect platform". How can I tell it that I'm on Un*x?

Beginners
1

Hi all!

I’m trying to build the LLVM-embedded-toolchain-for-Arm. I separately cloned the LLVM repo as instructed (I’m on tag llvmorg-16.0.0, commit 08d094a0e457). However, when building, CMake complains

CMake Error at /home/alessandro/tesi/LLVM-embedded-toolchain-for-Arm/repos/llvm-project/llvm/cmake/modules/HandleLLVMOptions.cmake:150 (MESSAGE):
  Unable to determine platform
Call Stack (most recent call first):
  CMakeLists.txt:157 (include)

The referenced file contains:

if(WIN32)
  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
  if(CYGWIN)
    set(LLVM_ON_WIN32 0)
    set(LLVM_ON_UNIX 1)
  else(CYGWIN)
    set(LLVM_ON_WIN32 1)
    set(LLVM_ON_UNIX 0)
  endif(CYGWIN)
else(WIN32)
  if(FUCHSIA OR UNIX)
    set(LLVM_ON_WIN32 0)
    set(LLVM_ON_UNIX 1)
    if(APPLE OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
      set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
    else()
      set(LLVM_HAVE_LINK_VERSION_SCRIPT 1)
    endif()
  else(FUCHSIA OR UNIX)
    MESSAGE(SEND_ERROR "Unable to determine platform") // <----- HERE
  endif(FUCHSIA OR UNIX)
endif(WIN32)

I can’t find the UNIX variable in the CMake files: how should I set it? I tried running CMake like

cmake -DLLVM_ENABLE_PROJECTS=clang -DCMAKE_BUILD_TYPE=Debug -DLLVM_USE_LINKER=lld -DLLVM_PARALLEL_LINK_JOBS=1 -G "Ninja" -B ./build -S ./llvm

but with no success.

What am I doing wrong?

Thanks!

2

UNIX is a CMake builtin variable (UNIX — CMake 3.26.1 Documentation). It should be set automatically.

3
  • What is your platform / operating system?
  • You should ask the embedded toolchain guys for help.
4

Yep that was my guess too.

Arch Linux

Do you mean the GH issues, or do you know of more specific places?

5 
message(STATUS "Using LLVM on: ${CMAKE_SYSTEM_NAME}")

As it is an LLVM file, you could temporarily hack the file.

6

It prints blank:

-- Using LLVM on:
7

Something is wrong with CMake on your platform or your CMake installation. Maybe try the latest binary packages from cmake.org and see if that works better.

8

Somehow, it seemed to be a problem of the actual LLVM codebase. Compiling main branch worked fine. This kinda closes the issue, but I wonder if it’s a problem of the LLVM repo or of the embedded toolchain