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On Windows, use the Python 'Activation Context' when loading extensions 

to avoid problems loading the CRT from a private assembly.  Via bug 4566.
This commit is contained in:
Mark Hammond 2009-01-27 23:12:23 +00:00
parent 560f9a8a90
commit 9f4f56d4e8
2 changed files with 76 additions and 2 deletions
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68
PC/dl_nt.c
View File

@ -18,6 +18,63 @@ char dllVersionBuffer[16] = ""; // a private buffer
HMODULE PyWin_DLLhModule = NULL;
const char *PyWin_DLLVersionString = dllVersionBuffer;
// Windows "Activation Context" work:
// Our .pyd extension modules are generally built without a manifest (ie,
// those included with Python and those built with a default distutils.
// This requires we perform some "activation context" magic when loading our
// extensions. In summary:
// * As our DLL loads we save the context being used.
// * Before loading our extensions we re-activate our saved context.
// * After extension load is complete we restore the old context.
// As an added complication, this magic only works on XP or later - we simply
// use the existence (or not) of the relevant function pointers from kernel32.
// See bug 4566 (http://python.org/sf/4566) for more details.
typedef BOOL (WINAPI * PFN_GETCURRENTACTCTX)(HANDLE *);
typedef BOOL (WINAPI * PFN_ACTIVATEACTCTX)(HANDLE, ULONG_PTR *);
typedef BOOL (WINAPI * PFN_DEACTIVATEACTCTX)(DWORD, ULONG_PTR);
typedef BOOL (WINAPI * PFN_ADDREFACTCTX)(HANDLE);
typedef BOOL (WINAPI * PFN_RELEASEACTCTX)(HANDLE);
// locals and function pointers for this activation context magic.
static HANDLE PyWin_DLLhActivationContext = NULL; // one day it might be public
static PFN_GETCURRENTACTCTX pfnGetCurrentActCtx = NULL;
static PFN_ACTIVATEACTCTX pfnActivateActCtx = NULL;
static PFN_DEACTIVATEACTCTX pfnDeactivateActCtx = NULL;
static PFN_ADDREFACTCTX pfnAddRefActCtx = NULL;
static PFN_RELEASEACTCTX pfnReleaseActCtx = NULL;
void _LoadActCtxPointers()
{
HINSTANCE hKernel32 = GetModuleHandleW(L"kernel32.dll");
if (hKernel32)
pfnGetCurrentActCtx = (PFN_GETCURRENTACTCTX) GetProcAddress(hKernel32, "GetCurrentActCtx");
// If we can't load GetCurrentActCtx (ie, pre XP) , don't bother with the rest.
if (pfnGetCurrentActCtx) {
pfnActivateActCtx = (PFN_ACTIVATEACTCTX) GetProcAddress(hKernel32, "ActivateActCtx");
pfnDeactivateActCtx = (PFN_DEACTIVATEACTCTX) GetProcAddress(hKernel32, "DeactivateActCtx");
pfnAddRefActCtx = (PFN_ADDREFACTCTX) GetProcAddress(hKernel32, "AddRefActCtx");
pfnReleaseActCtx = (PFN_RELEASEACTCTX) GetProcAddress(hKernel32, "ReleaseActCtx");
}
}
ULONG_PTR _Py_ActivateActCtx()
{
ULONG_PTR ret = 0;
if (PyWin_DLLhActivationContext && pfnActivateActCtx)
if (!(*pfnActivateActCtx)(PyWin_DLLhActivationContext, &ret)) {
OutputDebugString("Python failed to activate the activation context before loading a DLL\n");
ret = 0; // no promise the failing function didn't change it!
}
return ret;
}
void _Py_DeactivateActCtx(ULONG_PTR cookie)
{
if (cookie && pfnDeactivateActCtx)
if (!(*pfnDeactivateActCtx)(0, cookie))
OutputDebugString("Python failed to de-activate the activation context\n");
}
BOOL WINAPI DllMain (HANDLE hInst,
ULONG ul_reason_for_call,
@ -29,9 +86,18 @@ BOOL WINAPI DllMain (HANDLE hInst,
PyWin_DLLhModule = hInst;
// 1000 is a magic number I picked out of the air. Could do with a #define, I spose...
LoadString(hInst, 1000, dllVersionBuffer, sizeof(dllVersionBuffer));
//initall();
// and capture our activation context for use when loading extensions.
_LoadActCtxPointers();
if (pfnGetCurrentActCtx && pfnAddRefActCtx)
if ((*pfnGetCurrentActCtx)(&PyWin_DLLhActivationContext))
if (!(*pfnAddRefActCtx)(PyWin_DLLhActivationContext))
OutputDebugString("Python failed to load the default activation context\n");
break;
case DLL_PROCESS_DETACH:
if (pfnReleaseActCtx)
(*pfnReleaseActCtx)(PyWin_DLLhActivationContext);
break;
}
return TRUE;

10
Python/dynload_win.c
View File

@ -11,6 +11,10 @@
#include "importdl.h"
#include <windows.h>
// "activation context" magic - see dl_nt.c...
extern ULONG_PTR _Py_ActivateActCtx();
void _Py_DeactivateActCtx(ULONG_PTR cookie);
const struct filedescr _PyImport_DynLoadFiletab[] = {
#ifdef _DEBUG
{"_d.pyd", "rb", C_EXTENSION},
@ -172,6 +176,7 @@ dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
char pathbuf[260];
LPTSTR dummy;
unsigned int old_mode;
ULONG_PTR cookie = 0;
/* We use LoadLibraryEx so Windows looks for dependent DLLs
in directory of pathname first. However, Windows95
can sometimes not work correctly unless the absolute
@ -184,10 +189,13 @@ dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
if (GetFullPathName(pathname,
sizeof(pathbuf),
pathbuf,
&dummy))
&dummy)) {
ULONG_PTR cookie = _Py_ActivateActCtx();
/* XXX This call doesn't exist in Windows CE */
hDLL = LoadLibraryEx(pathname, NULL,
LOAD_WITH_ALTERED_SEARCH_PATH);
_Py_DeactivateActCtx(cookie);
}
/* restore old error mode settings */
SetErrorMode(old_mode);