Building the clangd LSP

[cellularmitosis]

I'm running into trouble when trying to build the clangd language server protocol using wasi-sdk on macOS 15.

I'm using the following script:

#!/bin/bash

set -e -o pipefail

export PATH="$HOME/opt/wasi-sdk-27.0-arm64-macos:$PATH"

export WASI_SDK_PATH="$HOME/opt/wasi-sdk-27.0-arm64-macos"
export WASI_TOOLCHAIN_FILE="${WASI_SDK_PATH}/share/cmake/wasi-sdk.cmake"

cd /tmp
rm -rf build-wasm
mkdir -p build-wasm
cd build-wasm

cmake -G "Unix Makefiles" \
    -DCMAKE_TOOLCHAIN_FILE="${WASI_TOOLCHAIN_FILE}" \
    -DCMAKE_SYSROOT="${WASI_SDK_PATH}/share/wasi-sysroot" \
    -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" \
    -DLLVM_INCLUDE_TESTS=OFF \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_INSTALL_PREFIX="$HOME/clangd-wasi" \
    -DCMAKE_CXX_FLAGS="-fno-exceptions" \
    -DLLVM_TARGETS_TO_BUILD="WebAssembly" \
    -DLLVM_DEFAULT_TARGET_TRIPLE="wasm32-wasi" \
    ../llvm-project-llvmorg-21.1.3/llvm

make -j8 clangd

When running cmake, I am stuck on the following error:

-- LLVM default target triple: wasm32-wasi
CMake Error at cmake/modules/HandleLLVMOptions.cmake:245 (MESSAGE):
  Unable to determine platform
Call Stack (most recent call first):
  CMakeLists.txt:1086 (include)

Unfortunately, I am not familiar enough with cmake to know what to try next to debug this problem. Any suggestions?

[cellularmitosis]

Full output attached.

output.txt

[cellularmitosis]

This is the relevant excerpt from HandleLLVMOptions.cmake:

if(WIN32 OR CYGWIN)
  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
  if(CYGWIN)
    set(LLVM_ON_WIN32 0)
    set(LLVM_ON_UNIX 1)
  else()
    set(LLVM_ON_WIN32 1)
    set(LLVM_ON_UNIX 0)
  endif()
elseif(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()
elseif(CMAKE_SYSTEM_NAME STREQUAL "Generic")
  set(LLVM_ON_WIN32 0)
  set(LLVM_ON_UNIX 0)
  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
else()
  MESSAGE(SEND_ERROR "Unable to determine platform")
endif()

[cellularmitosis]

I tried editing HandleLLVMOptions.cmake by adding the following clause:

elseif(CMAKE_SYSTEM_NAME STREQUAL "WASI")
  set(LLVM_ON_WIN32 0)
  set(LLVM_ON_UNIX 0)
  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)

This allowed cmake to exit successfully, however make then fails with:

[  1%] Configuring NATIVE LLVM...
[  1%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/APFixedPoint.cpp.obj
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/APFixedPoint.cpp:14:
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/ADT/APFixedPoint.h:19:
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/ADT/APSInt.h:18:
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/ADT/APInt.h:19:
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/MathExtras.h:16:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/ADT/bit.h:53:10: fatal error: 'machine/endian.h' file not found
   53 | #include <machine/endian.h>
      |          ^~~~~~~~~~~~~~~~~~

I was able to work-around this by creating a symlink:

wasi-sdk-27.0-arm64-macos/share/wasi-sysroot/include/wasm32-wasi/machine/endian.h -> wasi-sdk-27.0-arm64-macos/share/wasi-sysroot/include/wasm32-wasi/endian.h

However, that uncovered the next series of errors:

[  8%] Copying clang's mmintrin.h...
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/Caching.cpp:17:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/FileSystem.h:696:19: error: no member named 'getSize' in 'llvm::sys::fs::file_status'
  696 |   Result = Status.getSize();
      |            ~~~~~~ ^
[  8%] Copying clang's module.modulemap...
-- Looking for histedit.h - found
-- Found LibEdit: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.5.sdk/usr/include (found version "2.11")
-- Looking for arc4random
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CachePruning.cpp:18:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/FileSystem.h:696:19: error: no member named 'getSize' in 'llvm::sys::fs::file_status'
  696 |   Result = Status.getSize();
      |            ~~~~~~ ^
[  8%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/Compression.cpp.obj
[  8%] Copying clang's movdirintrin.h...
[  8%] Copying clang's movrs_avx10_2_512intrin.h...
/tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CachePruning.cpp:244:31: error: no member named 'getSize' in 'llvm::sys::fs::basic_file_status'
  244 |     TotalSize += StatusOrErr->getSize();
      |                  ~~~~~~~~~~~~~^
/tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CachePruning.cpp:245:52: error: no member named 'getSize' in 'llvm::sys::fs::basic_file_status'
  245 |     FileInfos.insert({FileAccessTime, StatusOrErr->getSize(), File->path()});
      |                                       ~~~~~~~~~~~~~^

[  9%] Copying clang's riscv_crypto.h...
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CodeGenCoverage.cpp:18:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/Process.h:112:34: error: use of undeclared identifier 'EnvPathSeparator'
  112 |                 char Separator = EnvPathSeparator);
      |                                  ^
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/Process.h:116:34: error: use of undeclared identifier 'EnvPathSeparator'
  116 |                 char Separator = EnvPathSeparator);
      |                                  ^

[ 11%] Copying clang's xsavesintrin.h...
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CommandLine.cpp:37:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/FileSystem.h:696:19: error: no member named 'getSize' in 'llvm::sys::fs::file_status'
  696 |   Result = Status.getSize();
      |            ~~~~~~ ^
[ 11%] Copying clang's xtestintrin.h...
[ 11%] Copying clang's zos_wrappers/builtins.h...
[ 11%] Copying clang's yvals_core.h...
In file included from /tmp/llvm-project-llvmorg-21.1.3/llvm/lib/Support/CommandLine.cpp:41:
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/Process.h:112:34: error: use of undeclared identifier 'EnvPathSeparator'
  112 |                 char Separator = EnvPathSeparator);
      |                                  ^
/tmp/llvm-project-llvmorg-21.1.3/llvm/include/llvm/Support/Process.h:116:34: error: use of undeclared identifier 'EnvPathSeparator'
  116 |                 char Separator = EnvPathSeparator);
      |                                  ^
3 errors generated.
[ 11%] Built target clang-resource-headers
make[3]: *** [lib/Support/CMakeFiles/LLVMSupport.dir/CodeGenCoverage.cpp.obj] Error 1
-- Looking for __deregister_frame - found
-- Looking for __unw_add_dynamic_fde
-- Looking for __unw_add_dynamic_fde - found
-- Looking for _Unwind_Backtrace
3 errors generated.
make[3]: *** [lib/Support/CMakeFiles/LLVMSupport.dir/CommandLine.cpp.obj] Error 1
make[2]: *** [lib/Support/CMakeFiles/LLVMSupport.dir/all] Error 2
make[2]: *** Waiting for unfinished jobs....

[sbc100]

There are several folks out there already trying (and some suceeding I believe) to build clang/llvm for WASI. See https://discourse.llvm.org/t/rfc-building-llvm-for-webassembly/79073 for example.