Fixing python 2.7 windows unicode issue with ``subprocess.Popen``.

win_subprocess.py

## issue: https://bugs.python.org/issue19264

import ctypes
import subprocess
import _subprocess
from ctypes import byref, windll, c_char_p, c_wchar_p, c_void_p, \
     Structure, sizeof, c_wchar, WinError
from ctypes.wintypes import BYTE, WORD, LPWSTR, BOOL, DWORD, LPVOID, \
     HANDLE


##
## Types
##

CREATE_UNICODE_ENVIRONMENT = 0x00000400
LPCTSTR = c_char_p
LPTSTR = c_wchar_p
LPSECURITY_ATTRIBUTES = c_void_p
LPBYTE  = ctypes.POINTER(BYTE)

class STARTUPINFOW(Structure):
    _fields_ = [
        ("cb",              DWORD),  ("lpReserved",    LPWSTR),
        ("lpDesktop",       LPWSTR), ("lpTitle",       LPWSTR),
        ("dwX",             DWORD),  ("dwY",           DWORD),
        ("dwXSize",         DWORD),  ("dwYSize",       DWORD),
        ("dwXCountChars",   DWORD),  ("dwYCountChars", DWORD),
        ("dwFillAtrribute", DWORD),  ("dwFlags",       DWORD),
        ("wShowWindow",     WORD),   ("cbReserved2",   WORD),
        ("lpReserved2",     LPBYTE), ("hStdInput",     HANDLE),
        ("hStdOutput",      HANDLE), ("hStdError",     HANDLE),
    ]

LPSTARTUPINFOW = ctypes.POINTER(STARTUPINFOW)


class PROCESS_INFORMATION(Structure):
    _fields_ = [
        ("hProcess",         HANDLE), ("hThread",          HANDLE),
        ("dwProcessId",      DWORD),  ("dwThreadId",       DWORD),
    ]

LPPROCESS_INFORMATION = ctypes.POINTER(PROCESS_INFORMATION)


class DUMMY_HANDLE(ctypes.c_void_p):

    def __init__(self, *a, **kw):
        super(DUMMY_HANDLE, self).__init__(*a, **kw)
        self.closed = False

    def Close(self):
        if not self.closed:
            windll.kernel32.CloseHandle(self)
            self.closed = True

    def __int__(self):
        return self.value


CreateProcessW = windll.kernel32.CreateProcessW
CreateProcessW.argtypes = [
    LPCTSTR, LPTSTR, LPSECURITY_ATTRIBUTES,
    LPSECURITY_ATTRIBUTES, BOOL, DWORD, LPVOID, LPCTSTR,
    LPSTARTUPINFOW, LPPROCESS_INFORMATION,
]
CreateProcessW.restype = BOOL


##
## Patched functions/classes
##

def CreateProcess(executable, args, _p_attr, _t_attr,
                  inherit_handles, creation_flags, env, cwd,
                  startup_info):
    """Create a process supporting unicode executable and args for win32

    Python implementation of CreateProcess using CreateProcessW for Win32

    """

    si = STARTUPINFOW(
        dwFlags=startup_info.dwFlags,
        wShowWindow=startup_info.wShowWindow,
        cb=sizeof(STARTUPINFOW),
        ## XXXvlab: not sure of the casting here to ints.
        hStdInput=int(startup_info.hStdInput),
        hStdOutput=int(startup_info.hStdOutput),
        hStdError=int(startup_info.hStdError),
    )

    wenv = None
    if env is not None:
        ## LPCWSTR seems to be c_wchar_p, so let's say CWSTR is c_wchar
        env = (unicode("").join([
            unicode("%s=%s\0") % (k, v)
            for k, v in env.items()])) + unicode("\0")
        wenv = (c_wchar * len(env))()
        wenv.value = env

    pi = PROCESS_INFORMATION()
    creation_flags |= CREATE_UNICODE_ENVIRONMENT

    if CreateProcessW(executable, args, None, None,
                      inherit_handles, creation_flags,
                      wenv, cwd, byref(si), byref(pi)):
        return (DUMMY_HANDLE(pi.hProcess), DUMMY_HANDLE(pi.hThread),
                pi.dwProcessId, pi.dwThreadId)
    raise WinError()


class Popen(subprocess.Popen):
    """This superseeds Popen and corrects a bug in cPython 2.7 implem"""

    def _execute_child(self, args, executable, preexec_fn, close_fds,
                       cwd, env, universal_newlines,
                       startupinfo, creationflags, shell, to_close,
                       p2cread, p2cwrite,
                       c2pread, c2pwrite,
                       errread, errwrite):
        """Code from part of _execute_child from Python 2.7 (9fbb65e)

        There are only 2 little changes concerning the construction of
        the the final string in shell mode: we preempt the creation of
        the command string when shell is True, because original function
        will try to encode unicode args which we want to avoid to be able to
        sending it as-is to ``CreateProcess``.

        """
        if not isinstance(args, subprocess.types.StringTypes):
            args = subprocess.list2cmdline(args)

        if startupinfo is None:
            startupinfo = subprocess.STARTUPINFO()
        if shell:
            startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW
            startupinfo.wShowWindow = _subprocess.SW_HIDE
            comspec = os.environ.get("COMSPEC", unicode("cmd.exe"))
            args = unicode('{} /c "{}"').format(comspec, args)
            if (_subprocess.GetVersion() >= 0x80000000 or
                    os.path.basename(comspec).lower() == "command.com"):
                w9xpopen = self._find_w9xpopen()
                args = unicode('"%s" %s') % (w9xpopen, args)
                creationflags |= _subprocess.CREATE_NEW_CONSOLE

        super(Popen, self)._execute_child(args, executable,
            preexec_fn, close_fds, cwd, env, universal_newlines,
            startupinfo, creationflags, False, to_close, p2cread,
            p2cwrite, c2pread, c2pwrite, errread, errwrite)

_subprocess.CreateProcess = CreateProcess

GREAT! It solved my problem. thanks!

Actually there is an issue in this patch. Since you patched _subprocess.CreateProcess, multiprocessing module will start using your version of CreateProcess now, and will fail at line 85, where startup_info could be None.

Thanks for this! I am forced to use python 2.7, so this saved not only my day, but my whole project!

PS: needed to add an "import os" for the "os.environ." & "os.path." calls...

@JokerQyou sorry for the late answer. Can you make a little test script to illustrate the problem, that would help tremendously for thinking about a fix. As of now, I have no idea of the context and why startup_info can be None. I'm sure this will make more sense with your example. Thanks for you report !

Very useful, thanks a lot!

I couldn't find a licence for your code on the page, did you have one in mind?

I'm not sure of the usage of this. I tried the following: 1) create file called win_subprocess.py 3) copy the contents above into it 3) included standard python header with utf-8 usage. 4) Use an if statement to include this file ONLY on Windows (below). 5) Include standard subprocess for any other platform 6) I also moved my library calls over to Popen. 7) make no other changes to my code?

I haven't had to do this type of modification in Python before. This type of thing is almost normal with #defines in C or C++. Can somebody confirm my steps? I'll try what I said below but thought this a good comment for others that follow.

For step 4 I do this:

sysPlat = sys.platform'
    if ( sysPlat == 'win32' or sysPlat == 'win64' ):
        import win_subprocess'
        from win_subprocess import CalledProcessError
    else:
        import subprocess
        from subprocess import CalledProcessError 

I'm about to move over to the Windows side and see if it works. :)

Could not get the patch to work. I guess my steps where not enough.

@KeithProctor, you just need to import win_subprocess at the start of your code for Windows platforms, after that use subprocess as normal. Something like this, based on what I think the above aims to do:

if sys.platform == 'win32':
    import win_subprocess
import subprocess
from subprocess import CalledProcessError 

Note that there is no 'win64' platform string - 32-bit and 64-bit Windows are both 'win32'. There's also something weird going on with quotes and leading whitespace in your code that would make it break.

Very cool - fixes the issue with minimal effort. Thanks a lot!