llvm - 如何使 emcc 工作？

Question

当我尝试使用 emcc 将 C 代码编译为 Javascript 时，收到以下错误:

emcc tests/hello_world.c 
CRITICAL root: fastcomp in use, but LLVM has not been built with the JavaScript backend as a target, llc reports:
===========================================================================
LLVM (http://llvm.org/):
  LLVM version 3.5.1
  Optimized build with assertions.
  Built Feb 22 2015 (00:08:56).
  Default target: x86_64-apple-darwin13.4.0
  Host CPU: corei7-avx

  Registered Targets:
    x86    - 32-bit X86: Pentium-Pro and above
    x86-64 - 64-bit X86: EM64T and AMD64
===========================================================================
CRITICAL root: you can fall back to the older (pre-fastcomp) compiler core, although that is not recommended, see https://github.com/kripken/emscripten/wiki/LLVM-Backend
INFO     root: (Emscripten: Running sanity checks)
CRITICAL root: failing sanity checks due to previous fastcomp failure

如何解决这个问题？如何回退到 pre-fast-comp？

Answer 1

我在从源代码手动构建 Emscripten 时解决了同样的错误。

Emscripten 使用自己的 LLVM 分支 - Fastcomp ;
按照说明从源代码构建它 here .然后编辑~/.emscripten有LLVM_ROOT像这样

LLVM_ROOT = os.path.expanduser('/home/yourpath/to/emscripten-fastcomp/build/Release/bin') # directory

(它甚至可以是 /home/yourpath/to/emscripten-fastcomp/build/bin )