CLI flag for accepting default visibility

[guybedford]

I've implemented this on top of #587 as well as rebasing at master...guybedford:no-export-hidden-update.

This supports the default behaviour of s2wasm, but then provides s2wasm --defaultVisibility to enable the behaviour from #587.

I didn't want to provide a PR, as these seem restricted by the contribution guidelines, but it's working well for me. Just let me know if a PR might be suitable (if I've even done this right!).

Note that when running ./check.py I'm getting the error -

(downloading waterfall 13645: https://storage.googleapis.com/wasm-llvm/builds/mac/13645/wasm-binaries-13645.tbz2)
Traceback (most recent call last):
  File "./check.py", line 24, in <module>
    from scripts.test.shared import (
  File "/Users/guybedford/Projects/binaryen/scripts/test/shared.py", line 235, in <module>
    fetch_waterfall()
  File "/Users/guybedford/Projects/binaryen/scripts/test/shared.py", line 203, in fetch_waterfall
    downloaded = urllib2.urlopen(url).read().strip()
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 154, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 437, in open
    response = meth(req, response)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 550, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 475, in error
    return self._call_chain(*args)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 409, in _call_chain
    result = func(*args)
  File "/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 558, in http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 404: Not Found

so wasn't able to verify the tests.

[pipcet]

As for the check.py issue, does check.py --no-test-waterfall work?

[guybedford]

@pipcet thanks I managed to get the s2wasm tests to pass that way. Although I still get:

build:  /usr/bin/gcc /Users/guybedford/Projects/binaryen/test/example/c-api-hello-world.c -c -o example.o -I/Users/guybedford/Projects/binaryen/src -g -Lbin/../lib -pthread
clang: warning: argument unused during compilation: '-Lbin/../lib'
   c-api-hello-world.c /Users/guybedford/Projects/binaryen/test/example/c-api-hello-world.c /Users/guybedford/Projects/binaryen/test/example/c-api-hello-world.txt
link:  /usr/bin/g++ -std=c++11 example.o -lbinaryen -I/Users/guybedford/Projects/binaryen/src -g -lasmjs -lsupport -Lbin/../lib -pthread -o bin/example -Wl,-rpath=$ORIGIN/../lib
clang: warning: argument unused during compilation: '-pthread'
ld: unknown option: -rpath=$ORIGIN/../lib
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Traceback (most recent call last):
  File "./check.py", line 455, in <module>
    os.remove(output_file)
OSError: [Errno 2] No such file or directory: 'bin/example'

at the end of the test run.

(The above is just my local setup obviously)...

[pipcet]

That looks like a clang-vs-gcc issue (as used for building binaryen, not for the wasm code :-) ). Does it happen with the vanilla tree? It might be worth filing a separate issue for that.