PC/dl_nt.c

   1 /*
   2
   3 Entry point for the Windows NT DLL.
   4
   5 About the only reason for having this, is so initall() can automatically
   6 be called, removing that burden (and possible source of frustration if
   7 forgotten) from the programmer.
   8
   9 */
  10
  11 #include "Python.h"
  12 #include "windows.h"
  13
  14 #ifdef Py_ENABLE_SHARED
  15 char dllVersionBuffer[16] = ""; // a private buffer
  16
  17 // Python Globals
  18 HMODULE PyWin_DLLhModule = NULL;
  19 const char *PyWin_DLLVersionString = dllVersionBuffer;
  20
  21 // Windows "Activation Context" work:
  22 // Our .pyd extension modules are generally built without a manifest (ie,
  23 // those included with Python and those built with a default distutils.
  24 // This requires we perform some "activation context" magic when loading our
  25 // extensions.  In summary:
  26 // * As our DLL loads we save the context being used.
  27 // * Before loading our extensions we re-activate our saved context.
  28 // * After extension load is complete we restore the old context.
  29 // As an added complication, this magic only works on XP or later - we simply
  30 // use the existence (or not) of the relevant function pointers from kernel32.
  31 // See bug 4566 (http://python.org/sf/4566) for more details.
  32
  33 typedef BOOL (WINAPI * PFN_GETCURRENTACTCTX)(HANDLE *);
  34 typedef BOOL (WINAPI * PFN_ACTIVATEACTCTX)(HANDLE, ULONG_PTR *);
  35 typedef BOOL (WINAPI * PFN_DEACTIVATEACTCTX)(DWORD, ULONG_PTR);
  36 typedef BOOL (WINAPI * PFN_ADDREFACTCTX)(HANDLE);
  37 typedef BOOL (WINAPI * PFN_RELEASEACTCTX)(HANDLE);
  38
  39 // locals and function pointers for this activation context magic.
  40 static HANDLE PyWin_DLLhActivationContext = NULL; // one day it might be public
  41 static PFN_GETCURRENTACTCTX pfnGetCurrentActCtx = NULL;
  42 static PFN_ACTIVATEACTCTX pfnActivateActCtx = NULL;
  43 static PFN_DEACTIVATEACTCTX pfnDeactivateActCtx = NULL;
  44 static PFN_ADDREFACTCTX pfnAddRefActCtx = NULL;
  45 static PFN_RELEASEACTCTX pfnReleaseActCtx = NULL;
  46
  47 void _LoadActCtxPointers()
  48 {
  49         HINSTANCE hKernel32 = GetModuleHandleW(L"kernel32.dll");
  50         if (hKernel32)
  51                 pfnGetCurrentActCtx = (PFN_GETCURRENTACTCTX) GetProcAddress(hKernel32, "GetCurrentActCtx");
  52         // If we can't load GetCurrentActCtx (ie, pre XP) , don't bother with the rest.
  53         if (pfnGetCurrentActCtx) {
  54                 pfnActivateActCtx = (PFN_ACTIVATEACTCTX) GetProcAddress(hKernel32, "ActivateActCtx");
  55                 pfnDeactivateActCtx = (PFN_DEACTIVATEACTCTX) GetProcAddress(hKernel32, "DeactivateActCtx");
  56                 pfnAddRefActCtx = (PFN_ADDREFACTCTX) GetProcAddress(hKernel32, "AddRefActCtx");
  57                 pfnReleaseActCtx = (PFN_RELEASEACTCTX) GetProcAddress(hKernel32, "ReleaseActCtx");
  58         }
  59 }
  60
  61 ULONG_PTR _Py_ActivateActCtx()
  62 {
  63         ULONG_PTR ret = 0;
  64         if (PyWin_DLLhActivationContext && pfnActivateActCtx)
  65                 if (!(*pfnActivateActCtx)(PyWin_DLLhActivationContext, &ret)) {
  66                         OutputDebugString("Python failed to activate the activation context before loading a DLL\n");
  67                         ret = 0; // no promise the failing function didn't change it!
  68                 }
  69         return ret;
  70 }
  71
  72 void _Py_DeactivateActCtx(ULONG_PTR cookie)
  73 {
  74         if (cookie && pfnDeactivateActCtx)
  75                 if (!(*pfnDeactivateActCtx)(0, cookie))
  76                         OutputDebugString("Python failed to de-activate the activation context\n");
  77 }
  78
  79 BOOL    WINAPI  DllMain (HANDLE hInst,
  80                                                 ULONG ul_reason_for_call,
  81                                                 LPVOID lpReserved)
  82 {
  83         switch (ul_reason_for_call)
  84         {
  85                 case DLL_PROCESS_ATTACH:
  86                         PyWin_DLLhModule = hInst;
  87                         // 1000 is a magic number I picked out of the air.  Could do with a #define, I spose...
  88                         LoadString(hInst, 1000, dllVersionBuffer, sizeof(dllVersionBuffer));
  89
  90                         // and capture our activation context for use when loading extensions.
  91                         _LoadActCtxPointers();
  92                         if (pfnGetCurrentActCtx && pfnAddRefActCtx)
  93                                 if ((*pfnGetCurrentActCtx)(&PyWin_DLLhActivationContext))
  94                                         if (!(*pfnAddRefActCtx)(PyWin_DLLhActivationContext))
  95                                                 OutputDebugString("Python failed to load the default activation context\n");
  96                         break;
  97
  98                 case DLL_PROCESS_DETACH:
  99                         if (pfnReleaseActCtx)
 100                                 (*pfnReleaseActCtx)(PyWin_DLLhActivationContext);
 101                         break;
 102         }
 103         return TRUE;
 104 }
 105
 106 #endif /* Py_ENABLE_SHARED */