Emscripten: compile a CPP file failed

[nerddan]

I cloned the repo from github on OS X.

➜  emscripten git:(master) ✗ ./em++
WARNING  root: (Emscripten: system change: 1.25.0|asmjs-unknown-emscripten|/Users/dan/Applications/clang+llvm-3.5.0-macosx-apple-darwin/bin|3.5.0 vs 1.25.0|le32-unknown-nacl|/Users/dan/Applications/clang+llvm-3.5.0-macosx-apple-darwin/bin|3.5.0, clearing cache)
WARNING  root: LLVM version appears incorrect (seeing "3.5.0", expected "3.3")
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 3.5.0
  Optimized build.
  Default target: x86_64-apple-darwin14.0.0
  Host CPU: core-avx2

  Registered Targets:
    aarch64    - AArch64 (little endian)
    aarch64_be - AArch64 (big endian)
    arm        - ARM
    arm64      - AArch64 (little endian)
    arm64_be   - AArch64 (big endian)
    armeb      - ARM (big endian)
    cpp        - C++ backend
    hexagon    - Hexagon
    mips       - Mips
    mips64     - Mips64 [experimental]
    mips64el   - Mips64el [experimental]
    mipsel     - Mipsel
    msp430     - MSP430 [experimental]
    nvptx      - NVIDIA PTX 32-bit
    nvptx64    - NVIDIA PTX 64-bit
    ppc32      - PowerPC 32
    ppc64      - PowerPC 64
    ppc64le    - PowerPC 64 LE
    r600       - AMD GPUs HD2XXX-HD6XXX
    sparc      - Sparc
    sparcv9    - Sparc V9
    systemz    - SystemZ
    thumb      - Thumb
    thumbeb    - Thumb (big endian)
    x86        - 32-bit X86: Pentium-Pro and above
    x86-64     - 64-bit X86: EM64T and AMD64
    xcore      - XCore
===========================================================================
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 fast comp failure

So I tried to disable _Fastcomp_.

➜  emscripten git:(master) ✗ EMCC_FAST_COMPILER=0 ./em++
WARNING  root: no input files

Compile something?

➜  emscripten git:(master) EMCC_FAST_COMPILER=0 ./em++ ../RegEx2DFA/src/RegEx2Dot.cpp
clang: warning: argument unused during compilation: '-nostdinc++'

/Users/dan/Documents/git/emscripten/src/compiler.js:330
  if (err.indexOf('Aborting compilation due to previous errors') != -1) {
          ^
TypeError: Object TypeError: Cannot read property 'length' of undefined has no method 'indexOf'
    at Object.<anonymous> (/Users/dan/Documents/git/emscripten/src/compiler.js:330:11)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3
Traceback (most recent call last):
  File "/Users/dan/Documents/git/emscripten/emscripten.py", line 1578, in <module>
    _main(environ=os.environ)
  File "/Users/dan/Documents/git/emscripten/emscripten.py", line 1566, in _main
    temp_files.run_and_clean(lambda: main(
  File "/Users/dan/Documents/git/emscripten/tools/tempfiles.py", line 39, in run_and_clean
    return func()
  File "/Users/dan/Documents/git/emscripten/emscripten.py", line 1574, in <lambda>
    DEBUG_CACHE=DEBUG_CACHE,
  File "/Users/dan/Documents/git/emscripten/emscripten.py", line 1461, in main
    jcache=jcache, temp_files=temp_files, DEBUG=DEBUG, DEBUG_CACHE=DEBUG_CACHE)
  File "/Users/dan/Documents/git/emscripten/emscripten.py", line 185, in emscript
    cwd=path_from_root('src'))
  File "/Users/dan/Documents/git/emscripten/tools/jsrun.py", line 43, in run_js
    raise Exception('Expected the command ' + str(command) + ' to finish with return code ' + str(assert_returncode) + ', but it returned with code ' + str(proc.returncode) + ' instead! Output: ' + str(ret)[:error_limit])
Exception: Expected the command ['/usr/local/bin/node', '/Users/dan/Documents/git/emscripten/src/compiler.js', '/tmp/tmpuaB_iw.txt', '/tmp/tmpgOKXAL.pre.ll', 'pre'] to finish with return code 0, but it returned with code 8 instead! Output: // Note: Some Emscripten settings will significantly limit the speed of the generated code.
// Note: Some Emscripten settings may limit the speed of the generated code.

[juj]

Setting up Emscripten compiler is more involved than just cloning the Emscripten repository. The problem with your first attempt is that you used Apple-provided Clang with Emscripten, which is a different fork of LLVM and not supported. Emscripten uses its own fork of LLVM instead, since a part of the development occurs in the LLVM side. The problem with the second attempt is that the non-fastcomp mode of build only supports the upstream Clang release version 3.3, again Apple-provided fork of Clang is not appropriate.

See the Getting Started documentation at http://kripken.github.io/emscripten-site/docs/getting_started/index.html on how to obtain and set up Emscripten either via manual git cloning or via emsdk.

[nerddan]

@juj Thank you for replying!
I was using the LLVM downloaded from http://llvm.org and I added LLVM_ROOT = '/Users/dan/Applications/clang+llvm-3.5.0-macosx-apple-darwin/bin' in ~/.emscripten. Is this version of LLVM available for Emscripten?
I got a network problem with the emsdk install method. (Have a problem with connection to AWS. Maybe due to GFW or something. I am in China.) But I can not find how to install via git cloning in the documentation.

[juj]

The upstream LLVM 3.5 is not supported, because Emscripten uses its own fork of LLVM. The documentation to install via git cloning is here: http://kripken.github.io/emscripten-site/docs/building_from_source/building_fastcomp_manually_from_source.html .

[nerddan]

@juj Just got Emscripten installed. I am exploring this magical compiler. Thank you so much!