emcc hello.c -s WASM=1 -o hello.html
WARNING:root:generating system library: libc.bc...
WARNING:root:                                     ok
WARNING:root:generating system library: dlmalloc.bc...
WARNING:root:                                         ok
build executables
WARNING:root:generating system asset: pack-asmjs.js...
WARNING:root:generating system library: libcxx_noexcept.a...
WARNING:root:                                               ok
WARNING:root:generating system library: libcxxabi.bc...
WARNING:root:                                          ok
WARNING:root:                                         ok
WARNING:root:generating system asset: load-wasm-worker.js...
WARNING:root:                                               ok
save the before js
process input
cannot use WASM=1 when full asm.js validation was disabled (make sure to run in at least -O1, and look for warnings about other options that might force asm.js off)
Traceback (most recent call last):
  File "/Development/projects/webassembly/emsdk_portable/emscripten/1.35.0/emcc", line 1835, in <module>
    subprocess.check_call([shared.PYTHON, shared.path_from_root('third_party', 'wasm-polyfill', 'wasmator.py'), js_target, wasm_target, shared.Settings.EXPORT_NAME])
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 541, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/local/opt/python/bin/python2.7', '/Development/projects/webassembly/emsdk_portable/emscripten/1.35.0/third_party/wasm-polyfill/wasmator.py', 'hello.js', 'hello.wasm', u'Module']' returned non-zero exit status 1