[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Eryk Sun]

Change by Eryk Sun :


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resolution:  -> out of date
stage: needs patch -> resolved
status: open -> closed

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Keno Fischer]

Keno Fischer added the comment:

Yes, you are correct about it being only an issue in the embedding context.
I agree that it might not be a good idea to do do this for every library, but I 
wanted to revive the discussion since this kind of thing seems like something 
that comes up frequently when people embed python. Thanks for the reference to 
the other thread. A solution that allows the activation context to be specified 
would be great.

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Eryk Sun]

Eryk Sun added the comment:

This is only a problem for ctypes when python27.dll is used in an application 
that isn't manifested to load the "Microsoft.VC90.CRT" assembly. ctypes doesn't 
have this problem for a regular script run via the 2.7 version of python.exe, 
since the loader uses the python.exe activation context. Daniel claimed 
otherwise, but his claim is demonstrably false. Maybe he was embedding Python.

Keno, I don't think it's a good idea to arbitrarily set the Python DLL's 
activation context every time ctypes calls LoadLibrary. I proposed a more 
generic solution in issue 24429, msg246754.

An alternative solution would be to implement a pure-Python activation context 
class that works as a Python context manager. For example, it could create and 
activate a context using the hModule and lpResourceName fields:

with ctypes.ACTCTX(module_handle=sys.dllhandle, 
   resource_name=2):
libc = ctypes.CDLL('msvcr90')

I have a Stack Overflow answer that demonstrates using activation contexts with 
ctypes:

http://stackoverflow.com/a/27392347/205580

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Keno Fischer]

Keno Fischer added the comment:

pyzmq has a similar issue. I believe one solution would be to call
`_Py_ActivateActCtx` in ctypes' load_library, i.e. do
```
#if HAVE_SXS
ULONG_PTR cookie = _Py_ActivateActCtx();
#endif
hMod = LoadLibraryW(name);
#if HAVE_SXS
_Py_DeactivateActCtx(cookie);
#endif
```
in that function. I don't know enough about python or ctypes to say whether 
this patch works as is (_Py_ActivateActCtx seems to be an internal function, 
not sure if ctypes has access to that).

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Christoph Gohlke]

Changes by Christoph Gohlke cgoh...@uci.edu:


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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Palm Kevin]

Palm Kevin added the comment:

+1

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Mark Dickinson]

Changes by Mark Dickinson dicki...@gmail.com:


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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Palm Kevin]

Palm Kevin added the comment:

Reproducible for Py 3.2.5

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versions: +Python 3.2

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Tom Edwards]

Tom Edwards added the comment:

Still an issue in 3.3.3. Igor's fix still works, thankfully.

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versions: +Python 3.3 -Python 2.7

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Tom Edwards]

Changes by Tom Edwards cont...@steamreview.org:


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versions: +Python 2.7

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Andrew Svetlov]

Changes by Andrew Svetlov andrew.svet...@gmail.com:


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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Igor Skochinsky]

Igor Skochinsky added the comment:

Just had this issue when using networkx (which imports uuid). One keyword that 
would help visibility is R6034 (the runtime error number). A couple of reports 
related to this:

https://projects.blender.org/tracker/index.php?func=detailaid=27666
http://forums.boxee.tv/showthread.php?t=15425

The proper solution is to fix ctypes, but in the meantime we can at least fix 
uuid. The error seems to be triggered by this snippet:

# The uuid_generate_* routines are provided by libuuid on at least
# Linux and FreeBSD, and provided by libc on Mac OS X.
for libname in ['uuid', 'c']:
try:
lib = ctypes.CDLL(ctypes.util.find_library(libname))
except:
continue
if hasattr(lib, 'uuid_generate_random'):
_uuid_generate_random = lib.uuid_generate_random
if hasattr(lib, 'uuid_generate_time'):
_uuid_generate_time = lib.uuid_generate_time

Since this code is useless on Windows, protecting it in if os.name not in 
['nt', 'ce'] does the trick.

BTW, instead of going all way with activation context etc., a simpler solution 
would be to add to ctypes something like this in CDLL.__init__:

if os.name in ['nt', 'ce'] and name == util.find_msvcrt():  # TODO: handle the 
extension
  self._handle = windll.kernel32.GetModuleHandleA(self._name)

i.e. use the already present runtime DLL instead of trying to load it again.

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Terry J. Reedy]

Changes by Terry J. Reedy tjre...@udel.edu:


--
nosy: +amaury.forgeotdarc, belopolsky, meador.inge
stage:  - needs patch
versions: +Python 2.7 -Python 3.5

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Ezio Melotti]

Ezio Melotti added the comment:

Thanks for the report.  Could you also provide a patch?

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[issue17213] ctypes loads wrong version of C runtime, leading to error message box from system

[Daniel Colascione]

New submission from Daniel Colascione:

Suppose we're running a Python program in an environment where PATH contains a 
directory that contains msvcr90.dll version A and that python27.exe is 
manifested to use msvcr90.dll version B, which is available in the SxS store 
but not on PATH.

Normally, python27.exe's side-by-side (SxS) manifest contains a description of 
*precisely* the correct version of msvcr90.dll to use, version B, so when 
python27.exe starts, the NT loader ignores msvcr90.dll version A and loads 
msvcr90.dll version B.

Everything works fine until somebody calls ctypes.CDLL(c); uuid.py, which 
tries to find uuid_generate_random in libc on module load, is an example of a 
component that unexpectedly tries to load libc through ctypes.

Now, when someone tried to load c, ctypes internally maps c to the C 
runtime library using ctypes.util.find_msvcrt, then calls _ctypes.LoadLibrary, 
which calls the Win32 API function LoadLibraryA. LoadLibraryA tries to find 
msvcr90.dll, but WITHOUT CONSULTING THE SXS ACTIVATION CONTEXT, meaning that 
LoadLibrary finds msvcr90.dll version A, not version B. msvcr90.dll version A 
isn't loaded yet, so the NT loader does the usual loading and initialization; 
msvcr90.dll version A's DllMain runs, notices that it's not being loaded as 
part of an SxS manifest, and presents the user with an R6034 error message, an 
application has made an attempt to laod the C runtime library incorrectly.

The overall result is that users of Python programs see error message popups 
from Microsoft Visual C++ Runtime Library that, in most cases, are completely 
benign. This problem doesn't occur if the correct version of msvcr90.dll 
happens to be in PATH.

One solution is to have _ctypes.LoadLibrary use the correct activation context; 
another is to use GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS, 
(LPCTSTR) fopen, module) to retrieve a handle to the current C runtime 
library without having to go through LoadLibrary at all.

--
components: ctypes
messages: 182212
nosy: dancol
priority: normal
severity: normal
status: open
title: ctypes loads wrong version of C runtime, leading to error message box 
from system
type: behavior
versions: Python 3.5

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