万花筒示例代码在使用 LLVM 的 MacOS 上编译错误(8|10)

Question

Compiling kaleidoscope tutorial code fails with clang++ -g -O3 toy.cpp $(llvm-config --cxxflags) -std=c++17 (as the example goes) and outputs the following error:

Undefined symbols for architecture x86_64:
  "llvm::DisableABIBreakingChecks", referenced from:
      llvm::VerifyDisableABIBreakingChecks in toy-e1a114.o
ld: symbol(s) not found for architecture x86_64
clang-8: error: linker command failed with exit code 1 (use -v to see invocation)

LLVM were installed with brew install llvm (version 10 when this question is posted), later changed to brew install llvm@8 .

Interesting thing is, removing header llvm/ADT/STLExtras.h actually solves this. But I'm afraid removing this will not be a general solution.

Answer 1

I think the problem might be that $(llvm-config --cxxflags) doesn't work properly in macOS. I don't know exactly what it is with --cxxflags , but I personally experienced a problem that $(llvm-config --libfiles) didn't return the correct path to the shared library libLLVM in macOS (that command worked in Linux anyway).

However, I suggest to use CMake, which you will need anyway when working with LLVM. Below is a sample CMake code copied fromthe LLVM website . I followed this CMake code and can compile my project in macOS.

cmake_minimum_required(VERSION 3.4.3)
project(SimpleProject)

find_package(LLVM REQUIRED CONFIG)

message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")

# Set your project compile flags.
# E.g. if using the C++ header files
# you will need to enable C++11 support
# for your compiler.

include_directories(${LLVM_INCLUDE_DIRS})
add_definitions(${LLVM_DEFINITIONS})

# Now build our tools
add_executable(simple-tool tool.cpp)

# Find the libraries that correspond to the LLVM components
# that we wish to use
llvm_map_components_to_libnames(llvm_libs support core irreader)

# Link against LLVM libraries
target_link_libraries(simple-tool ${llvm_libs})