Eryk Sun <[email protected]> added the comment:
It may suit the needs of NumPy and SciPy to use an assembly for DLL
dependencies. With an assembly it's possible for two DLLs with the same name to
load in a process and possible for a DLL to extend the assembly search path
with up to nine relative paths at load time. The target directory can be up to
two levels above the DLL directory (e.g. "..\..\assembly_dir"). An assembly can
thus be packaged as a common dependency for other packages, and packages can
depend on different versions of the assembly.
For example, let's make a package that changes the _tkinter.pyd extension
module to use a private assembly, which consists of the two DLL dependencies,
"tcl86t.dll" and "tk86t.dll".
Begin by copying "DLLs\_tkinter.pyd" to a package directory such as
"Lib\site-packages\mytk". Modify the embedded #2 manifest in "_tkinter.pyd"
(use mt.exe, or a GUI resource editor) to include a dependency on an assembly
named "amd64_tcl_tk_8.6.6.0":
<dependency>
<dependentAssembly>
<assemblyIdentity name="amd64_tcl_tk_8.6.6.0"
version="8.6.6.0"
type="win32"
processorArchitecture="amd64" />
</dependentAssembly>
</dependency>
Next, add the following component configuration file beside the extension
module, named "_tkinter.pyd.2.config":
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<configuration>
<windows>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<probing privatePath="..\__winsxs__" />
</assemblyBinding>
</windows>
</configuration>
This extends the assembly probing path that's used by the Fusion loader in the
session server (csrss.exe). The Fusion loader probes for the assembly in four
locations per directory. It checks for the assembly both as a DLL and as a
manifest file, both in the directory and in a subdirectory that's named for the
assembly. We'll be using a subdirectory with a manifest.
"..\__winsxs__" resolves to "site-packages\__winsxs__". Create this directory
and a subdirectory named "amd64_tcl_tk_8.6.6.0". To this, add the two DLL
dependencies -- tcl86t.dll and tk86t.dll -- plus the following manifest file
named "amd64_tcl_tk_8.6.6.0.manifest":
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
<assemblyIdentity name="amd64_tcl_tk_8.6.6.0"
version="8.6.6.0"
type="win32"
processorArchitecture="amd64" />
<file name="tcl86t.dll" />
<file name="tk86t.dll" />
</assembly>
That's all it takes. If configured properly, you should be able to import the
extension module via `from mytk import _tkinter`.
This will work in a virtual environment. However, I haven't checked whether the
loader handles private assemblies in the same way in a store app. That's off my
radar.
> packages need to adopt to calling AddDllDirectory. As long as
> python is built with ctypes, this is easy enough to adopt, even
> though there are some caveats
Avoid using ctypes.windll in libraries. It caches the ctypes.WinDLL instance,
which caches function pointers. Projects that use the same DLLs thus can
interfere with each other by setting incompatible prototypes. It also doesn't
allow us to enable use_last_error to get reliable error handling. Also, the
DLL_DIRECTORY_COOKIE return value is a pointer type, not a 32-bit integer. Even
if we're not using it to cleanup afterwards (i.e. AddDllDirectory;
LoadLibraryExW; RemoveDllDirectory), which we should be doing, we need the full
64-bit value to reliably check for failure (NULL). By some fluke, the low DWORD
of the cookie could be 0.
Here are the ctypes definitions using a private WinDLL instance and an errcheck
function:
import ctypes
from ctypes import wintypes
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
LOAD_LIBRARY_SEARCH_DEFAULT_DIRS = 0x00001000
DLL_DIRECTORY_COOKIE = wintypes.LPVOID
def _errcheck_zero(result, func, args):
if not result:
raise ctypes.WinError(ctypes.get_last_error())
return args
kernel32.AddDllDirectory.errcheck = _errcheck_zero
kernel32.AddDllDirectory.restype = DLL_DIRECTORY_COOKIE
kernel32.AddDllDirectory.argtypes = (wintypes.LPCWSTR,)
kernel32.RemoveDllDirectory.errcheck = _errcheck_zero
kernel32.RemoveDllDirectory.argtypes = (DLL_DIRECTORY_COOKIE,)
kernel32.LoadLibraryExW.errcheck = _errcheck_zero
kernel32.LoadLibraryExW.restype = wintypes.HMODULE
kernel32.LoadLibraryExW.argtypes = (
wintypes.LPCWSTR, wintypes.HANDLE, wintypes.DWORD)
Don't call SetDefaultDllDirectories. Use LoadLibraryExW(path, None,
LOAD_LIBRARY_SEARCH_DEFAULT_DIRS).
----------
nosy: +eryksun
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