patch for ruby-oci8 2.0.4. See http://rubyforge.org/forum/forum.php?thread_id=49751&forum_id=1078

errhp.patch

Index: ext/oci8/oci8.h
===================================================================
--- ext/oci8/oci8.h	(revision 411)
+++ ext/oci8/oci8.h	(working copy)
@@ -174,7 +174,7 @@
 
 /* macros to access thread-local storage.
  *
- *  int oci8_tls_key_init(oci8_tls_key_t *key);
+ *  int oci8_tls_key_init(oci8_tls_key_t *key, void (*destructor)(void*));
  *    initialie a key to access thread-local storege
  *    This returns 0 on success or error number.
  *
@@ -190,7 +190,7 @@
 #if defined(_WIN32)
 #include <windows.h>
 #define oci8_tls_key_t           DWORD
-#define oci8_tls_key_init(key_p) \
+#define oci8_tls_key_init(key_p, dummy) \
     ((*(key_p) = TlsAlloc()), \
     (*(key_p) == 0xFFFFFFFF) ? GetLastError() : 0)
 #define oci8_tls_get(key)        TlsGetValue(key)
@@ -198,7 +198,7 @@
 #elif defined(HAVE_PTHREAD_H)
 #include <pthread.h>
 #define oci8_tls_key_t           pthread_key_t
-#define oci8_tls_key_init(key_p) pthread_key_create((key_p), NULL)
+#define oci8_tls_key_init(key_p, destructor) pthread_key_create((key_p), destructor)
 #define oci8_tls_get(key)        pthread_getspecific(key)
 #define oci8_tls_set(key, val)   pthread_setspecific((key), (val))
 #else
Index: ext/oci8/env.c
===================================================================
--- ext/oci8/env.c	(revision 411)
+++ ext/oci8/env.c	(working copy)
@@ -48,17 +48,42 @@
  */
 
 oci8_tls_key_t oci8_tls_key; /* native thread key */
-static ID id_thread_key;     /* ruby's thread key */
 
-static void oci8_free_errhp(OCIError *errhp)
+static void oci8_free_errhp(void *errhp)
 {
     OCIHandleFree(errhp, OCI_HTYPE_ERROR);
 }
 
+#ifdef WIN32
+__declspec(dllexport)
+BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
+{
+    void *errhp;
+
+    switch (fdwReason) {
+    case DLL_PROCESS_ATTACH:
+        /* do nothing */
+        break;
+    case DLL_THREAD_ATTACH:
+        /* do nothing */
+        break;
+    case DLL_THREAD_DETACH:
+        errhp = oci8_tls_get(oci8_tls_key);
+        if (errhp != NULL) {
+            oci8_free_errhp(errhp);
+        }
+        break;
+    case DLL_PROCESS_DETACH:
+        /* do nothing */
+        break;
+    }
+    return TRUE;
+}
+#endif
+
 OCIError *oci8_make_errhp(void)
 {
     OCIError *errhp;
-    VALUE obj;
     sword rv;
 
     /* create a new errhp. */
@@ -66,15 +91,6 @@
     if (rv != OCI_SUCCESS) {
         oci8_env_raise(oci8_envhp, rv);
     }
-    /* create a new ruby object which contains errhp to make
-     * sure that the errhp is freed when it become unnecessary.
-     */
-    obj = Data_Wrap_Struct(rb_cObject, NULL, oci8_free_errhp, errhp);
-    /* set the ruby object to ruby's thread local storage to prevent
-     * it from being freed while the thread is available.
-     */
-    rb_thread_local_aset(rb_thread_current(), id_thread_key, obj);
-
     oci8_tls_set(oci8_tls_key, (void*)errhp);
     return errhp;
 }
@@ -148,8 +164,7 @@
     }
 
 #ifdef RUBY_VM
-    id_thread_key = rb_intern("__oci8_errhp__");
-    error = oci8_tls_key_init(&oci8_tls_key);
+    error = oci8_tls_key_init(&oci8_tls_key, oci8_free_errhp);
     if (error != 0) {
         rb_raise(rb_eRuntimeError, "Cannot create thread local key (errno = %d)", error);
     }