install fails on arch linux because "cl" command exists, but is something different

[f0rki]

I'm having trouble getting the latest pyvex to work on arch linux. I'm using a virtualenv. Install works fine with pip. When I try to import pyvex, I get the following error:

$ python -c 'import pyvex'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/pyvex/__init__.py", line 31, in <module>
    pvc = _find_c_lib()
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/pyvex/__init__.py", line 23, in _find_c_lib
    ffi.cdef(_ffi_str)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/api.py", line 105, in cdef
    self._cdef(csource, override=override, packed=packed)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/api.py", line 119, in _cdef
    self._parser.parse(csource, override=override, **options)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/cparser.py", line 299, in parse
    self._internal_parse(csource)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/cparser.py", line 304, in _internal_parse
    ast, macros, csource = self._parse(csource)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/cparser.py", line 262, in _parse
    self.convert_pycparser_error(e, csource)
  File "~/.virtualenvs/pyvex/lib/python2.7/site-packages/cffi/cparser.py", line 291, in convert_pycparser_error
    raise api.CDefError(msg)
cffi.api.CDefError: cannot parse "extern VexControl vex_control;"
:3:19: before: vex_control

Apparently the file _ffi_str variable contains only the string "extern VexControl vex_control;".

After some digging I came to the conclusion that the issues is in make_ffi.py#L58. The first tried command is cl. This is a binary that does something completely different (apparently part of the cliquer package) on my system.
This fails silently as there is no check for Popen.returncode. Maybe using subprocess.check_output would be better suited here, since it throws an exception on non-zero exit status?

After switching cmd1 and cmd2, it properly generates the file (with pip install -e .). But I guess this might break other systems...

[ltfish]

Good finding!

Since cffi is essential for angr as of now, I think we can do the following:

• Make the path to cl and cpp configurable in PyVEX (and SimuVEX).
• Add some simple checks at import time to make sure cl and cpp are indeed what we are expecting, otherwise display an error message, asking users to properly set the path to cl and cpp.

@rhelmot any comment on this?