From 649f9f6dc6312f75c434a669a81b8bf2aaa929a4 Mon Sep 17 00:00:00 2001
From: Jeff Hill <johill@lanl.gov>
Date: Mon, 11 Apr 2005 18:29:52 +0000
Subject: [PATCH] make certain that com.dll remains resident for its daemon
 threads even if the user explicitly uloads it (from a labView DLL)

---
 src/libCom/osi/os/WIN32/osdThread.c | 71 +++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/src/libCom/osi/os/WIN32/osdThread.c b/src/libCom/osi/os/WIN32/osdThread.c
index 21dd9c7e3..501e07db9 100644
--- a/src/libCom/osi/os/WIN32/osdThread.c
+++ b/src/libCom/osi/os/WIN32/osdThread.c
@@ -94,6 +94,76 @@ static const int osdRealtimePriorityList [osdRealtimePriorityStateCount] =
     6  // allowed on >= W2k, but no #define supplied
 };
 
+#if !defined(EPICS_DLL_NO)
+BOOL WINAPI DllMain (
+    HANDLE hModule, DWORD dwReason, LPVOID lpReserved )
+{
+    static DWORD dllHandleIndex;
+    HMODULE dllHandle;
+    BOOL success = TRUE;
+
+    switch ( dwReason ) 
+	{
+	case DLL_PROCESS_ATTACH:
+        dllHandleIndex = TlsAlloc ();
+        if ( dllHandleIndex == TLS_OUT_OF_INDEXES ) {
+            success = FALSE;
+        }
+		break;
+
+	case DLL_PROCESS_DETACH:
+        success = TlsFree ( dllHandleIndex );
+		break;
+
+	case DLL_THREAD_ATTACH:
+        /*
+         * Dont allow user's explicitly calling FreeLibrary for Com.dll to yank 
+         * the carpet out from under EPICS threads that are still using Com.dll
+         */
+#if _WIN32_WINNT >= 0x0501 
+        /* 
+         * Only in WXP 
+         * Thats a shame becaus ethis is probably much faster
+         */
+        success = GetModuleHandleEx (
+            GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
+            ( LPCTSTR ) DllMain, & dllHandle );
+#else
+        {   
+            char name[256];
+            DWORD nChar = GetModuleFileName ( 
+                hModule, name, sizeof ( name ) );
+            if ( nChar && nChar < sizeof ( name ) ) {
+                dllHandle = LoadLibrary ( name );
+                if ( ! dllHandle ) {
+                    success = FALSE;
+                }
+            }
+            else {
+                success = FALSE;
+            }
+        }
+#endif
+        if ( success ) {
+            success = TlsSetValue ( dllHandleIndex, dllHandle );
+        }
+		break;
+	case DLL_THREAD_DETACH:
+        /*
+         * Thread is exiting, release Com.dll. I am assuming that windows is
+         * smart enough to postpone the unload until this function returns.
+         */
+        dllHandle = TlsGetValue ( dllHandleIndex );
+        if ( dllHandle ) {
+            success = FreeLibrary ( dllHandle );
+        }
+		break;
+	}
+
+	return success;
+}
+#endif
+
 /*
  * fetchWin32ThreadGlobal ()
  * Search for "Synchronization and Multiprocessor Issues" in ms doc
@@ -520,6 +590,7 @@ epicsShareFunc epicsThreadId epicsShareAPI epicsThreadCreate (const char *pName,
     if ( ! pGbl )  {
         return NULL;
     }
+
     pParmWIN32 = epicsThreadParmCreate ( pName );
     if ( pParmWIN32 == 0 ) {
         return ( epicsThreadId ) pParmWIN32;