未定义对“LLVMLinkInMCJIT”的引用

Question

每当调用此函数时，

//===-- MCJIT.h - MC-Based Just-In-Time Execution Engine --------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file forces the MCJIT to link in on certain operating systems.
// (Windows).
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_EXECUTIONENGINE_MCJIT_H
#define LLVM_EXECUTIONENGINE_MCJIT_H

#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include <cstdlib>

extern "C" void LLVMLinkInMCJIT();

namespace {
  struct ForceMCJITLinking {
    ForceMCJITLinking() {
      // We must reference MCJIT in such a way that compilers will not
      // delete it all as dead code, even with whole program optimization,
      // yet is effectively a NO-OP. As the compiler isn't smart enough
      // to know that getenv() never returns -1, this will do the job.
      // This is so that globals in the translation units where these functions
      // are defined are forced to be initialized, populating various
      // registries.
      if (std::getenv("bar") != (char*) -1)
        return;

      LLVMLinkInMCJIT();
    }
  } ForceMCJITLinking;
}

#endif

我发现以下错误：

/usr/bin/ld: CMakeFiles/vm-llvm-example.dir/example/main.cpp.o: in function `_GLOBAL__sub_I_main.cpp':
/home/pegasus/Documents/llvm-project/llvm/include/llvm/ExecutionEngine/MCJIT.h:35:(.text.startup+0x25e): undefined reference to `LLVMLinkInMCJIT'

错误源自这一行

extern "C" void LLVMLinkInMCJIT();

它说找不到“LLVMLinkInMCJIT”的函数定义。我该如何修复这个错误？

Answer 1

对于 llvm > 16，我必须包含此内容。

#include <llvm/ExecutionEngine/MCJIT.h>