LLVM 15.0.0-rc2: compiler_rt does not build out of the box on older macOS: Failed to determine SDK version for "iphonesimulator" SDK

[debohman]

CMake Error at /tera/tera/debo/Projects/llvm/llvmorg-15.0.0-rc2/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake:73 (message):
  Failed to determine SDK version for "iphonesimulator" SDK
Call Stack (most recent call first):
  /tera/tera/debo/Projects/llvm/llvmorg-15.0.0-rc2/compiler-rt/cmake/builtin-config-ix.cmake:120 (find_darwin_sdk_version)
  CMakeLists.txt:51 (include)


-- Configuring incomplete, errors occurred!
See also "/tera/tera/debo/Projects/llvm/llvmorg-15.0.0-rc2-build/runtimes/builtins-bins/CMakeFiles/CMakeOutput.log".
See also "/tera/tera/debo/Projects/llvm/llvmorg-15.0.0-rc2-build/runtimes/builtins-bins/CMakeFiles/CMakeError.log".
FAILED: runtimes/builtins-stamps/builtins-configure /tera/tera/debo/Projects/llvm/llvmorg-15.0.0-rc2-build/runtimes/builtins-stamps/builtins-configure

Configuration:

cmake -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_EXE_LINKER_FLAGS=-L/usr/local/lib -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind;compiler-rt" ../llvmorg-15.0.0-rc2/llvm

I was able to build it by changing the configuration in build/runtimes/builtins-bins/CMakeCache.txt:

COMPILER_RT_ENABLE_IOS:BOOL=OFF

macOS 10.12.6
cmake version 3.24.0

[carlocab]

You can pass

-DBUILTINS_CMAKE_ARGS=-DCOMPILER_RT_ENABLE_IOS=OFF

to your cmake invocation to avoid having to edit a CMakeCache.txt.

[carlocab]

Since #57362 is now closed, I'll copy my comment from there in case it might be useful:

You need an Xcode installation to build 15.0.0-rc2. The CLT alone does not suffice, at least not without an extra CMake flag. I've been meaning to file an issue about this for a few days now, but I haven't gotten around to it. But this is a regression against 14.0.6.

The errant commit seems to be a680c21.

A workaround is to pass

-DBUILTINS_CMAKE_ARGS=-DCOMPILER_RT_ENABLE_IOS=OFF

to your cmake invocation, if you don't want to use a full Xcode installation. It would be nice for a CLT-only build to just work without needing the flag above, since it's rather arcane.

Related discussion at Homebrew/homebrew-core#106925 (comment).

[balay]

Hm -DBUILTINS_CMAKE_ARGS=-DCOMPILER_RT_ENABLE_IOS=OFF does not work for me. Attaching the log

spack-build-out.txt

[debohman]

The workaround was successful for me. This is bootstrapping using llvm-14.0.6 and cmake-3.24.1.

ETA: This is building llvm-15.0.0-rc3.

[balay]

I tried the alternate fix - and could make progress

--- a/compiler-rt/cmake/base-config-ix.cmake    2022-08-25 17:44:01.000000000 -0500
+++ b/compiler-rt/cmake/base-config-ix.cmake    2022-08-25 17:42:05.000000000 -0500
@@ -145,7 +145,7 @@
                    "-darwin-target-variant" "x86_64-apple-ios13.1-macabi"
                    "-Werror")
   option(COMPILER_RT_ENABLE_MACCATALYST "Enable building for Mac Catalyst" ${COMPILER_RT_HAS_DARWIN_TARGET_VARIANT_FLAG})
-  option(COMPILER_RT_ENABLE_IOS "Enable building for iOS" On)
+  option(COMPILER_RT_ENABLE_IOS "Enable building for iOS" Off)
   option(COMPILER_RT_ENABLE_WATCHOS "Enable building for watchOS - Experimental" Off)
   option(COMPILER_RT_ENABLE_TVOS "Enable building for tvOS - Experimental" Off)
 

However got build errors (with native compilers)
clt-spack-build-out.txt
Then I tried gcc from brew - and got similar errors.

This is bootstrapping using llvm-14.0.6

Ah so - I tried using (previously installed) llvm-14.0.6 - and that worked!

balay@ypro spack % /Users/balay/spack/opt/spack/darwin-catalina-skylake/clang-14.0.6/llvm-15.0.0-rc2-5lploygnzkvgilunkqbdffoecobed6vu/bin/clang-format --version
clang-format version 15.0.0

[carlocab]

Hm -DBUILTINS_CMAKE_ARGS=-DCOMPILER_RT_ENABLE_IOS=OFF does not work for me. Attaching the log

spack-build-out.txt

This is because you pass compiler-rt to LLVM_ENABLE_PROJECTS. Pass it to LLVM_ENABLE_RUNTIMES instead. You don't need to adjust your compiler to a recent-ish LLVM if you do this (since LLVM_ENABLE_RUNTIMES will use the just-built clang compiler to build compiler-rt).

[balay]

Ah - ok. That's whats currently in spack recipe for llvm. [hence in the current build]

setting compiler-rt via LLVM_ENABLE_RUNTIMES gets DBUILTINS_CMAKE_ARGS=-DCOMPILER_RT_ENABLE_IOS=OFF working

'-DLLVM_ENABLE_PROJECTS:STRING=lldb;clang;clang-tools-extra;lld;compiler-rt;libcxx;libcxxabi;libunwind;polly'

the build failure was in libcxxabi - so I guess that should also be switched? Ok - switched libcxx ,libcxxabi and the build now goes through with apple compilers.

[carlocab]

Generally I'd recommend passing arguments to LLVM_ENABLE_RUNTIMES whenever possible.

This works for libcxx, libcxxabi, compiler-rt, libunwind, and openmp. (And libc, but I have no idea if that works on macOS.)

From the build docs on LLVM_ENABLE_RUNTIMES:

This is the correct way to build runtimes when putting together a toolchain. It will build the builtins separately from the other runtimes to preserve correct dependency ordering.

[balay]

Since what version of llvm is it recommended to use LLVM_ENABLE_RUNTIMES [instead of LLVM_ENABLE_PROJECTS] for the above?