问题描述
我正在学习llvm，并想对我的想法做一个概念证明.
I am learning llvm and wanted to do a proof of concept of an idea I have.
基本上，我想拆分我的编译器和运行时.编译器将提供一个.bc，运行时将通过ParseBitcodeFile加载它，并使用ExecutionEngine来运行它.这部分正在工作.
Basically, I want to split my compiler and my runtime. The compiler would give a .bc and the runtime would load it via ParseBitcodeFile and use the ExecutionEngine to run it. This part is working.
现在，为了轻松进行系统调用，我希望能够在我的运行时C/C ++函数中实现所有系统调用(文件io，stdout打印等).我的问题是，如何从我的玩具编译器的代码中调用这些函数，该玩具编译器由llvm在不同的步骤中进行编译，并允许它们在执行时使用.
Now, to make system calls easily, I want to be able to implement in my runtime C/C++ functions which do all the system calls (file io, stdout printing, etc). My question is, how could I call these functions from the code from my toy compiler, which is compiled in a different step by llvm, and allow it to be used when executed.
推荐答案
好消息:使用JIT ExecutionEngine时，这将正常工作.当JIT-er找到IR本身未找到的IR使用的外部符号时，它会在JIT-ing过程本身中查找，因此可以调用宿主程序中可见的任何符号.
Good news: when using the JIT ExecutionEngine, this will just work. When the JIT-er finds an external symbol used by the IR which is not found in the IR itself, it looks in the JIT-ing process itself, so any symbols visible from your host program can be called.
在LLVM教程的第4部分第4部分中直接对此进行了解释:
This is explained directly in part 4 of the LLVM tutorial:
有关gory的详细信息，请参见lib/ExecutionEngine/JIT/JIT.cpp-特别是DynamicLibrary的用法.
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