[svn-r16474] Purpose: fix problems related to 'self-referential' attributes

Description:
When an attribute was created with a datatype or dataspace that was shared in
the same object header that the attribute was in, the attribute could not be
deleted.  Changes made to ensure that the attribute can be deleted both when the
attribute is in the object header and when it is shared in the heap.  Object
header message decode routines now take an "open_oh" parameter to enable them to
avoid opening the same object header twice.

Tested: jam, smirom (h5committest)

35 files changed, 217 insertions, 152 deletions

diff --git a/src/H5Abtree2.c b/src/H5Abtree2.c
index 07550da..da4ad86 100644
--- a/src/H5Abtree2.c
+++ b/src/H5Abtree2.c
@@ -168,7 +168,7 @@ H5A_dense_fh_name_cmp(const void *obj, size_t UNUSED obj_len, void *_udata)
     FUNC_ENTER_NOAPI_NOINIT(H5A_dense_fh_name_cmp)
 
     /* Decode attribute information */
-    if(NULL == (attr = (H5A_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_ATTR_ID, (const unsigned char *)obj)))
+    if(NULL == (attr = (H5A_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_ATTR_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "can't decode attribute")
 
     /* Compare the string values */
diff --git a/src/H5Adense.c b/src/H5Adense.c
index 76ab95d..bc5ddfb 100644
--- a/src/H5Adense.c
+++ b/src/H5Adense.c
@@ -806,7 +806,7 @@ H5A_dense_copy_fh_cb(const void *obj, size_t UNUSED obj_len, void *_udata)
      *  HDF5 routine, it could attempt to re-protect that direct block for the
      *  heap, causing the HDF5 routine called to fail)
      */
-    if(NULL == (udata->attr = (H5A_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_ATTR_ID, (const unsigned char *)obj)))
+    if(NULL == (udata->attr = (H5A_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_ATTR_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDECODE, FAIL, "can't decode attribute")
 
     /* Set the creation order index for the attribute */
diff --git a/src/H5Gbtree2.c b/src/H5Gbtree2.c
index d060a11..c16fc16 100644
--- a/src/H5Gbtree2.c
+++ b/src/H5Gbtree2.c
@@ -164,7 +164,7 @@ H5G_dense_fh_name_cmp(const void *obj, size_t UNUSED obj_len, void *_udata)
     FUNC_ENTER_NOAPI_NOINIT(H5G_dense_fh_name_cmp)
 
     /* Decode link information */
-    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "can't decode link")
 
     /* Compare the string values */
diff --git a/src/H5Gdense.c b/src/H5Gdense.c
index 6c3a171..2bca4fa 100644
--- a/src/H5Gdense.c
+++ b/src/H5Gdense.c
@@ -566,7 +566,7 @@ H5G_dense_lookup_by_idx_fh_cb(const void *obj, size_t UNUSED obj_len, void *_uda
     FUNC_ENTER_NOAPI_NOINIT(H5G_dense_lookup_by_idx_fh_cb)
 
     /* Decode link information & keep a copy */
-    if(NULL == (tmp_lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (tmp_lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "can't decode link")
 
     /* Copy link information */
@@ -852,7 +852,7 @@ H5G_dense_iterate_fh_cb(const void *obj, size_t UNUSED obj_len, void *_udata)
      *  HDF5 routine, it could attempt to re-protect that direct block for the
      *  heap, causing the HDF5 routine called to fail - QAK)
      */
-    if(NULL == (udata->lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (udata->lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "can't decode link")
 
 done:
@@ -1047,7 +1047,7 @@ H5G_dense_get_name_by_idx_fh_cb(const void *obj, size_t UNUSED obj_len, void *_u
     FUNC_ENTER_NOAPI_NOINIT(H5G_dense_get_name_by_idx_fh_cb)
 
     /* Decode link information */
-    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "can't decode link")
 
     /* Get the length of the name */
@@ -1245,7 +1245,7 @@ H5G_dense_remove_fh_cb(const void *obj, size_t UNUSED obj_len, void *_udata)
     FUNC_ENTER_NOAPI_NOINIT(H5G_dense_remove_fh_cb)
 
     /* Decode link information */
-    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, FAIL, "can't decode link")
 
     /* Check for removing the link from the creation order index */
@@ -1408,7 +1408,7 @@ H5G_dense_remove_by_idx_fh_cb(const void *obj, size_t UNUSED obj_len, void *_uda
     FUNC_ENTER_NOAPI_NOINIT(H5G_dense_remove_by_idx_fh_cb)
 
     /* Decode link information */
-    if(NULL == (udata->lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, H5O_LINK_ID, (const unsigned char *)obj)))
+    if(NULL == (udata->lnk = (H5O_link_t *)H5O_msg_decode(udata->f, udata->dxpl_id, NULL, H5O_LINK_ID, (const unsigned char *)obj)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTDECODE, H5_ITER_ERROR, "can't decode link")
 
     /* Can't operate on link here because the fractal heap block is locked */
diff --git a/src/H5HFcache.c b/src/H5HFcache.c
index 8b29bc7..96ffe2d 100644
--- a/src/H5HFcache.c
+++ b/src/H5HFcache.c
@@ -387,7 +387,7 @@ HDfprintf(stderr, "%s: Load heap header, addr = %a\n", FUNC, addr);
         UINT32DECODE(p, hdr->pline_root_direct_filter_mask);
 
         /* Decode I/O filter information */
-        if(NULL == (pline = (H5O_pline_t *)H5O_msg_decode(hdr->f, dxpl_id, H5O_PLINE_ID, p)))
+        if(NULL == (pline = (H5O_pline_t *)H5O_msg_decode(hdr->f, dxpl_id, NULL, H5O_PLINE_ID, p)))
             HGOTO_ERROR(H5E_HEAP, H5E_CANTDECODE, NULL, "can't decode I/O pipeline filters")
         p += hdr->filter_len;
 
diff --git a/src/H5O.c b/src/H5O.c
index 73c8e73..8c8ace0 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -1393,9 +1393,9 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_link
+ * Function:	H5O_link_oh
  *
- * Purpose:	Adjust the link count for an object header by adding
+ * Purpose:	Adjust the link count for an open object header by adding
  *		ADJUST to the link count.
  *
  * Return:	Success:	New link count
@@ -1409,24 +1409,12 @@ done:
  *-------------------------------------------------------------------------
  */
 int
-H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
+H5O_link_oh(H5F_t *f, int adjust, hid_t dxpl_id, H5O_t *oh, unsigned *oh_flags)
 {
-    H5O_t	*oh = NULL;
-    H5AC_protect_t oh_acc;              /* Access mode for protecting object header */
-    unsigned oh_flags = H5AC__NO_FLAGS_SET; /* Whether the object was deleted  */
+    haddr_t addr = H5O_OH_GET_ADDR(oh);     /* Object header address */
     int	ret_value;                          /* Return value */
 
-    FUNC_ENTER_NOAPI(H5O_link, FAIL)
-
-    /* check args */
-    HDassert(loc);
-    HDassert(loc->file);
-    HDassert(H5F_addr_defined(loc->addr));
-
-    /* get header */
-    oh_acc = adjust ? H5AC_WRITE : H5AC_READ;
-    if(NULL == (oh = (H5O_t *)H5AC_protect(loc->file, dxpl_id, H5AC_OHDR, loc->addr, NULL, NULL, oh_acc)))
-	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header")
+    FUNC_ENTER_NOAPI(H5O_link_oh, FAIL)
 
     /* Check for adjusting link count */
     if(adjust) {
@@ -1435,38 +1423,38 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
             if((unsigned)(-adjust) > oh->nlink)
                 HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "link count would be negative")
             oh->nlink += adjust;
-            oh_flags |= H5AC__DIRTIED_FLAG;
+            *oh_flags |= H5AC__DIRTIED_FLAG;
 
             /* Check if the object should be deleted */
             if(oh->nlink == 0) {
                 /* Check if the object is still open by the user */
-                if(H5FO_opened(loc->file, loc->addr) != NULL) {
+                if(H5FO_opened(f, addr) != NULL) {
                     /* Flag the object to be deleted when it's closed */
-                    if(H5FO_mark(loc->file, loc->addr, TRUE) < 0)
+                    if(H5FO_mark(f, addr, TRUE) < 0)
                         HGOTO_ERROR(H5E_OHDR, H5E_CANTDELETE, FAIL, "can't mark object for deletion")
                 } /* end if */
                 else {
                     /* Delete object right now */
-                    if(H5O_delete_oh(loc->file, dxpl_id, oh) < 0)
+                    if(H5O_delete_oh(f, dxpl_id, oh) < 0)
                         HGOTO_ERROR(H5E_OHDR, H5E_CANTDELETE, FAIL, "can't delete object from file")
 
                     /* Mark the object header as deleted */
-                    oh_flags = H5AC__DELETED_FLAG | H5AC__FREE_FILE_SPACE_FLAG;
+                    *oh_flags = H5AC__DELETED_FLAG | H5AC__FREE_FILE_SPACE_FLAG;
                 } /* end else */
             } /* end if */
         } else {
             /* A new object, or one that will be deleted */
             if(oh->nlink == 0) {
                 /* Check if the object is current open, but marked for deletion */
-                if(H5FO_marked(loc->file, loc->addr) > 0) {
+                if(H5FO_marked(f, addr) > 0) {
                     /* Remove "delete me" flag on the object */
-                    if(H5FO_mark(loc->file, loc->addr, FALSE) < 0)
+                    if(H5FO_mark(f, addr, FALSE) < 0)
                         HGOTO_ERROR(H5E_OHDR, H5E_CANTDELETE, FAIL, "can't mark object for deletion")
                 } /* end if */
             } /* end if */
 
             oh->nlink += adjust;
-            oh_flags |= H5AC__DIRTIED_FLAG;
+            *oh_flags |= H5AC__DIRTIED_FLAG;
         } /* end if */
 
         /* Check for operations on refcount message */
@@ -1475,7 +1463,7 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
             if(oh->has_refcount_msg) {
                 /* Check for removing refcount message */
                 if(oh->nlink <= 1) {
-                    if(H5O_msg_remove_real(loc->file, oh, H5O_MSG_REFCOUNT, H5O_ALL, NULL, NULL, TRUE, dxpl_id) < 0)
+                    if(H5O_msg_remove_real(f, oh, H5O_MSG_REFCOUNT, H5O_ALL, NULL, NULL, TRUE, dxpl_id) < 0)
                         HGOTO_ERROR(H5E_ATTR, H5E_CANTDELETE, FAIL, "unable to delete refcount message")
                     oh->has_refcount_msg = FALSE;
                 } /* end if */
@@ -1483,7 +1471,7 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
                 else {
                     H5O_refcount_t refcount = oh->nlink;
 
-                    if(H5O_msg_write_real(loc->file, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
+                    if(H5O_msg_write_real(f, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
                         HGOTO_ERROR(H5E_ATTR, H5E_CANTUPDATE, FAIL, "unable to update refcount message")
                 } /* end else */
             } /* end if */
@@ -1492,7 +1480,7 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
                 if(oh->nlink > 1) {
                     H5O_refcount_t refcount = oh->nlink;
 
-                    if(H5O_msg_append_real(loc->file, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
+                    if(H5O_msg_append_real(f, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
                         HGOTO_ERROR(H5E_ATTR, H5E_CANTINSERT, FAIL, "unable to create new refcount message")
                     oh->has_refcount_msg = TRUE;
                 } /* end if */
@@ -1504,6 +1492,51 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
     ret_value = oh->nlink;
 
 done:
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* end H5O_link_oh() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5O_link
+ *
+ * Purpose:	Adjust the link count for an object header by adding
+ *		ADJUST to the link count.
+ *
+ * Return:	Success:	New link count
+ *
+ *		Failure:	Negative
+ *
+ * Programmer:	Robb Matzke
+ *		matzke@llnl.gov
+ *		Aug  5 1997
+ *
+ *-------------------------------------------------------------------------
+ */
+int
+H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
+{
+    H5O_t	*oh = NULL;
+    H5AC_protect_t oh_acc;              /* Access mode for protecting object header */
+    unsigned oh_flags = H5AC__NO_FLAGS_SET; /* Whether the object was deleted  */
+    int	ret_value;                          /* Return value */
+
+    FUNC_ENTER_NOAPI(H5O_link, FAIL)
+
+    /* check args */
+    HDassert(loc);
+    HDassert(loc->file);
+    HDassert(H5F_addr_defined(loc->addr));
+
+    /* get header */
+    oh_acc = adjust ? H5AC_WRITE : H5AC_READ;
+    if(NULL == (oh = (H5O_t *)H5AC_protect(loc->file, dxpl_id, H5AC_OHDR, loc->addr, NULL, NULL, oh_acc)))
+	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header")
+
+    /* Call the "real" link routine */
+    if((ret_value = H5O_link_oh(loc->file, adjust, dxpl_id, oh, &oh_flags)) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust object link count")
+
+done:
     if(oh && H5AC_unprotect(loc->file, dxpl_id, H5AC_OHDR, loc->addr, oh, oh_flags) < 0)
 	HDONE_ERROR(H5E_OHDR, H5E_PROTECT, FAIL, "unable to release object header")
 
diff --git a/src/H5Oainfo.c b/src/H5Oainfo.c
index 7f6a55d..667f28c 100644
--- a/src/H5Oainfo.c
+++ b/src/H5Oainfo.c
@@ -35,8 +35,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_ainfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_ainfo_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_ainfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_ainfo_copy(const void *_mesg, void *_dest);
 static size_t H5O_ainfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -105,8 +105,8 @@ H5FL_DEFINE_STATIC(H5O_ainfo_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_ainfo_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_ainfo_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_ainfo_t	*ainfo = NULL;  /* Attribute info */
     unsigned char flags;        /* Flags for encoding attribute info */
diff --git a/src/H5Oattr.c b/src/H5Oattr.c
index b875d02..b375791 100644
--- a/src/H5Oattr.c
+++ b/src/H5Oattr.c
@@ -27,8 +27,8 @@
 
 /* PRIVATE PROTOTYPES */
 static herr_t H5O_attr_encode(H5F_t *f, uint8_t *p, const void *mesg);
-static void *H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_attr_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static void *H5O_attr_copy(const void *_mesg, void *_dest);
 static size_t H5O_attr_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_attr_free(void *mesg);
@@ -121,7 +121,7 @@ H5FL_EXTERN(H5S_extent_t);
     function using malloc() and is returned to the caller.
 --------------------------------------------------------------------------*/
 static void *
-H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
+H5O_attr_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, unsigned UNUSED mesg_flags,
     unsigned *ioflags, const uint8_t *p)
 {
     H5A_t		*attr = NULL;
@@ -182,7 +182,8 @@ H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
         p += name_len;    /* advance the memory pointer */
 
     /* Decode the attribute's datatype */
-    if(NULL == (attr->shared->dt = (H5T_t *)(H5O_MSG_DTYPE->decode)(f, dxpl_id, ((flags & H5O_ATTR_FLAG_TYPE_SHARED) ? H5O_MSG_FLAG_SHARED : 0), ioflags, p)))
+    if(NULL == (attr->shared->dt = (H5T_t *)(H5O_MSG_DTYPE->decode)(f, dxpl_id, open_oh,
+        ((flags & H5O_ATTR_FLAG_TYPE_SHARED) ? H5O_MSG_FLAG_SHARED : 0), ioflags, p)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDECODE, NULL, "can't decode attribute datatype")
     if(attr->shared->version < H5O_ATTR_VERSION_2)
         p += H5O_ALIGN_OLD(attr->shared->dt_size);
@@ -196,7 +197,8 @@ H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
 	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* Decode attribute's dataspace extent */
-    if((extent = (H5S_extent_t *)(H5O_MSG_SDSPACE->decode)(f, dxpl_id, ((flags & H5O_ATTR_FLAG_SPACE_SHARED) ? H5O_MSG_FLAG_SHARED : 0), ioflags, p)) == NULL)
+    if((extent = (H5S_extent_t *)(H5O_MSG_SDSPACE->decode)(f, dxpl_id, open_oh,
+        ((flags & H5O_ATTR_FLAG_SPACE_SHARED) ? H5O_MSG_FLAG_SHARED : 0), ioflags, p)) == NULL)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDECODE, NULL, "can't decode attribute dataspace")
 
     /* Copy the extent information to the dataspace */
diff --git a/src/H5Obogus.c b/src/H5Obogus.c
index c257ca4..cee3199 100644
--- a/src/H5Obogus.c
+++ b/src/H5Obogus.c
@@ -38,8 +38,8 @@
 #ifdef H5O_ENABLE_BOGUS
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_bogus_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_bogus_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_bogus_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static size_t H5O_bogus_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_bogus_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
@@ -87,8 +87,8 @@ const H5O_msg_class_t H5O_MSG_BOGUS[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_bogus_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_bogus_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_bogus_t *mesg = NULL;
     void *ret_value;            /* Return value */
diff --git a/src/H5Obtreek.c b/src/H5Obtreek.c
index 36e4c1a..99e6bdd 100644
--- a/src/H5Obtreek.c
+++ b/src/H5Obtreek.c
@@ -28,8 +28,8 @@
 #include "H5Opkg.h"             /* Object headers			*/
 #include "H5MMprivate.h"	/* Memory management			*/
 
-static void  *H5O_btreek_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void  *H5O_btreek_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_btreek_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void  *H5O_btreek_copy(const void *_mesg, void *_dest);
 static size_t H5O_btreek_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -79,8 +79,8 @@ const H5O_msg_class_t H5O_MSG_BTREEK[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_btreek_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_btreek_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_btreek_t	*mesg;          /* Native message */
     void                *ret_value;     /* Return value */
diff --git a/src/H5Ocache.c b/src/H5Ocache.c
index db093a4..551eca8 100644
--- a/src/H5Ocache.c
+++ b/src/H5Ocache.c
@@ -536,7 +536,7 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
                 unsigned ioflags = 0;   /* Flags for decode routine */
 
                 /* Decode continuation message */
-                cont = (H5O_cont_t *)(H5O_MSG_CONT->decode)(f, dxpl_id, 0, &ioflags, oh->mesg[curmesg].raw);
+                cont = (H5O_cont_t *)(H5O_MSG_CONT->decode)(f, dxpl_id, NULL, 0, &ioflags, oh->mesg[curmesg].raw);
                 cont->chunkno = oh->nchunks;	/*the next chunk to allocate */
 
                 /* Save 'native' form of continuation message */
@@ -559,7 +559,7 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
 
                 /* Decode ref. count message */
                 HDassert(oh->version > H5O_VERSION_1);
-                refcount = (H5O_refcount_t *)(H5O_MSG_REFCOUNT->decode)(f, dxpl_id, 0, &ioflags, oh->mesg[curmesg].raw);
+                refcount = (H5O_refcount_t *)(H5O_MSG_REFCOUNT->decode)(f, dxpl_id, NULL, 0, &ioflags, oh->mesg[curmesg].raw);
 
                 /* Save 'native' form of ref. count message */
                 oh->mesg[curmesg].native = refcount;
diff --git a/src/H5Ocont.c b/src/H5Ocont.c
index b3f178d..df336dd 100644
--- a/src/H5Ocont.c
+++ b/src/H5Ocont.c
@@ -37,8 +37,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_cont_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_cont_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_cont_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static size_t H5O_cont_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_cont_free(void *mesg);
@@ -90,8 +90,8 @@ H5FL_DEFINE(H5O_cont_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_cont_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_cont_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_cont_t             *cont = NULL;
     void                   *ret_value;
diff --git a/src/H5Odrvinfo.c b/src/H5Odrvinfo.c
index 9aafe41..864fe9e 100644
--- a/src/H5Odrvinfo.c
+++ b/src/H5Odrvinfo.c
@@ -28,8 +28,8 @@
 #include "H5Opkg.h"             /* Object headers			*/
 #include "H5MMprivate.h"	/* Memory management			*/
 
-static void  *H5O_drvinfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void  *H5O_drvinfo_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_drvinfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void  *H5O_drvinfo_copy(const void *_mesg, void *_dest);
 static size_t H5O_drvinfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -80,8 +80,8 @@ const H5O_msg_class_t H5O_MSG_DRVINFO[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_drvinfo_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_drvinfo_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_drvinfo_t	*mesg;          /* Native message */
     void                *ret_value;     /* Return value */
diff --git a/src/H5Odtype.c b/src/H5Odtype.c
index 71692c1..24e443c 100644
--- a/src/H5Odtype.c
+++ b/src/H5Odtype.c
@@ -29,8 +29,8 @@
 
 /* PRIVATE PROTOTYPES */
 static herr_t H5O_dtype_encode(H5F_t *f, uint8_t *p, const void *mesg);
-static void *H5O_dtype_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_dtype_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static void *H5O_dtype_copy(const void *_mesg, void *_dest);
 static size_t H5O_dtype_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_dtype_reset(void *_mesg);
@@ -990,7 +990,7 @@ done:
     function using malloc() and is returned to the caller.
 --------------------------------------------------------------------------*/
 static void *
-H5O_dtype_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
+H5O_dtype_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh, unsigned UNUSED mesg_flags,
     unsigned *ioflags/*in,out*/, const uint8_t *p)
 {
     H5T_t	*dt = NULL;
diff --git a/src/H5Oefl.c b/src/H5Oefl.c
index ee51e1c..5702b34 100644
--- a/src/H5Oefl.c
+++ b/src/H5Oefl.c
@@ -29,8 +29,8 @@
 #include "H5Opkg.h"             /* Object headers			*/
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_efl_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_efl_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_efl_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_efl_copy(const void *_mesg, void *_dest);
 static size_t H5O_efl_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -84,8 +84,8 @@ const H5O_msg_class_t H5O_MSG_EFL[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_efl_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_efl_decode(H5F_t *f, hid_t dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_efl_t		*mesg = NULL;
     int			version;
diff --git a/src/H5Ofill.c b/src/H5Ofill.c
index 02706ec..d5345aa 100644
--- a/src/H5Ofill.c
+++ b/src/H5Ofill.c
@@ -33,12 +33,12 @@
 #include "H5Sprivate.h"		/* Dataspaces				*/
 
 
-static void  *H5O_fill_old_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void  *H5O_fill_old_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_fill_old_encode(H5F_t *f, uint8_t *p, const void *_mesg);
 static size_t H5O_fill_old_size(const H5F_t *f, const void *_mesg);
-static void  *H5O_fill_new_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void  *H5O_fill_new_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_fill_new_encode(H5F_t *f, uint8_t *p, const void *_mesg);
 static size_t H5O_fill_new_size(const H5F_t *f, const void *_mesg);
 static void  *H5O_fill_copy(const void *_mesg, void *_dest);
@@ -182,8 +182,8 @@ H5FL_BLK_EXTERN(type_conv);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_fill_new_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_fill_new_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_fill_t	*fill = NULL;
     void	*ret_value;
@@ -296,8 +296,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_fill_old_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_fill_old_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_fill_t *fill = NULL;		/* Decoded fill value message */
     void *ret_value;                    /* Return value */
diff --git a/src/H5Oginfo.c b/src/H5Oginfo.c
index 2323fff..83a6085 100644
--- a/src/H5Oginfo.c
+++ b/src/H5Oginfo.c
@@ -33,8 +33,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_ginfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_ginfo_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_ginfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_ginfo_copy(const void *_mesg, void *_dest);
 static size_t H5O_ginfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -95,8 +95,8 @@ H5FL_DEFINE_STATIC(H5O_ginfo_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_ginfo_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_ginfo_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_ginfo_t         *ginfo = NULL;  /* Pointer to group information message */
     unsigned char       flags;          /* Flags for encoding group info */
diff --git a/src/H5Olayout.c b/src/H5Olayout.c
index f914006..73d2c81 100644
--- a/src/H5Olayout.c
+++ b/src/H5Olayout.c
@@ -33,8 +33,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_layout_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_layout_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_layout_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_layout_copy(const void *_mesg, void *_dest);
 static size_t H5O_layout_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -93,8 +93,8 @@ H5FL_DEFINE(H5O_layout_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_layout_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_layout_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_layout_t           *mesg = NULL;
     unsigned               u;
diff --git a/src/H5Olinfo.c b/src/H5Olinfo.c
index d1eb2c0..5ba237a 100644
--- a/src/H5Olinfo.c
+++ b/src/H5Olinfo.c
@@ -35,8 +35,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_linfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_linfo_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_linfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_linfo_copy(const void *_mesg, void *_dest);
 static size_t H5O_linfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -111,8 +111,8 @@ H5FL_DEFINE_STATIC(H5O_linfo_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_linfo_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_linfo_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_linfo_t	*linfo = NULL;  /* Link info */
     unsigned char index_flags;  /* Flags for encoding link index info */
diff --git a/src/H5Olink.c b/src/H5Olink.c
index a4449f0..96d4747 100644
--- a/src/H5Olink.c
+++ b/src/H5Olink.c
@@ -38,8 +38,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_link_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_link_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_link_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_link_copy(const void *_mesg, void *_dest);
 static size_t H5O_link_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -116,8 +116,8 @@ H5FL_DEFINE_STATIC(H5O_link_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_link_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_link_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_link_t          *lnk = NULL;    /* Pointer to link message */
     size_t              len = 0;        /* Length of a string in the message */
diff --git a/src/H5Omessage.c b/src/H5Omessage.c
index a63299a..286240c 100644
--- a/src/H5Omessage.c
+++ b/src/H5Omessage.c
@@ -1804,10 +1804,16 @@ done:
  *		slu@ncsa.uiuc.edu
  *		July 14, 2004
  *
+ * Modifications: Neil Fortner
+ *              Feb 4 2009
+ *              Added open_oh parameter.  This parameter is optional and
+ *              contains this message's protected object header
+ *
  *-------------------------------------------------------------------------
  */
 void *
-H5O_msg_decode(H5F_t *f, hid_t dxpl_id, unsigned type_id, const unsigned char *buf)
+H5O_msg_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, unsigned type_id,
+    const unsigned char *buf)
 {
     const H5O_msg_class_t   *type;      /* Actual H5O class type for the ID */
     void *ret_value;                    /* Return value */
@@ -1822,7 +1828,7 @@ H5O_msg_decode(H5F_t *f, hid_t dxpl_id, unsigned type_id, const unsigned char *b
     HDassert(type);
 
     /* decode */
-    if((ret_value = (type->decode)(f, dxpl_id, 0, &ioflags, buf)) == NULL)
+    if((ret_value = (type->decode)(f, dxpl_id, open_oh, 0, &ioflags, buf)) == NULL)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "unable to decode message")
 
 done:
diff --git a/src/H5Omtime.c b/src/H5Omtime.c
index 46272a0..1bbcfe3 100644
--- a/src/H5Omtime.c
+++ b/src/H5Omtime.c
@@ -28,13 +28,13 @@
 #include "H5Opkg.h"             /* Object headers			*/
 
 
-static void *H5O_mtime_new_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_mtime_new_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_mtime_new_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static size_t H5O_mtime_new_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 
-static void *H5O_mtime_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_mtime_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_mtime_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_mtime_copy(const void *_mesg, void *_dest);
 static size_t H5O_mtime_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -119,8 +119,8 @@ H5FL_DEFINE(time_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_mtime_new_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_mtime_new_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     time_t	*mesg;
     uint32_t    tmp_time;       /* Temporary copy of the time */
@@ -172,8 +172,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_mtime_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_mtime_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     time_t	*mesg, the_time;
     int	i;
diff --git a/src/H5Oname.c b/src/H5Oname.c
index 915546b..5ffa870 100644
--- a/src/H5Oname.c
+++ b/src/H5Oname.c
@@ -33,8 +33,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_name_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_name_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_name_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_name_copy(const void *_mesg, void *_dest);
 static size_t H5O_name_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -84,8 +84,8 @@ const H5O_msg_class_t H5O_MSG_NAME[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_name_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_name_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_name_t          *mesg;
     void                *ret_value;     /* Return value */
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index fa69b93..4bc6d26 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -187,7 +187,7 @@
                                                                               \
         /* Decode the message */                                              \
         HDassert(msg_type->decode);                                           \
-        if(NULL == ((MSG)->native = (msg_type->decode)((F), (DXPL), (MSG)->flags, &ioflags, (MSG)->raw))) \
+        if(NULL == ((MSG)->native = (msg_type->decode)((F), (DXPL), (OH), (MSG)->flags, &ioflags, (MSG)->raw))) \
             HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, ERR, "unable to decode message") \
                                                                               \
         /* Mark the message dirty if it was changed by decoding */            \
@@ -222,7 +222,7 @@ struct H5O_msg_class_t {
     const char	*name;				/*for debugging             */
     size_t	native_size;			/*size of native message    */
     unsigned    share_flags;			/* Message sharing settings */
-    void	*(*decode)(H5F_t*, hid_t, unsigned, unsigned *, const uint8_t *);
+    void	*(*decode)(H5F_t*, hid_t, H5O_t *, unsigned, unsigned *, const uint8_t *);
     herr_t	(*encode)(H5F_t*, hbool_t, uint8_t*, const void *);
     void	*(*copy)(const void *, void *);	/*copy native value         */
     size_t	(*raw_size)(const H5F_t *, hbool_t, const void *);/*sizeof encoded message	*/
@@ -515,8 +515,8 @@ H5_DLL herr_t H5O_release_mesg(H5F_t *f, hid_t dxpl_id, H5O_t *oh,
     H5O_mesg_t *mesg, hbool_t adj_link);
 
 /* Shared object operators */
-H5_DLL void * H5O_shared_decode(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
-    const uint8_t *buf, const H5O_msg_class_t *type);
+H5_DLL void * H5O_shared_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned *ioflags, const uint8_t *buf, const H5O_msg_class_t *type);
 H5_DLL herr_t H5O_shared_encode(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *sh_mesg);
 H5_DLL size_t H5O_shared_size(const H5F_t *f, const H5O_shared_t *sh_mesg);
 H5_DLL herr_t H5O_shared_delete(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
diff --git a/src/H5Opline.c b/src/H5Opline.c
index fed2861..20a9d26 100644
--- a/src/H5Opline.c
+++ b/src/H5Opline.c
@@ -33,8 +33,8 @@
 
 /* PRIVATE PROTOTYPES */
 static herr_t H5O_pline_encode(H5F_t *f, uint8_t *p, const void *mesg);
-static void *H5O_pline_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_pline_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static void *H5O_pline_copy(const void *_mesg, void *_dest);
 static size_t H5O_pline_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_pline_reset(void *_mesg);
@@ -107,8 +107,8 @@ H5FL_DEFINE(H5O_pline_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_pline_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_pline_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_pline_t		*pline = NULL;          /* Pipeline message */
     H5Z_filter_info_t   *filter;                /* Filter to decode */
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index fe04df1..fd6f265 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -567,6 +567,7 @@ H5_DLL herr_t H5O_create(H5F_t *f, hid_t dxpl_id, size_t size_hint,
 H5_DLL herr_t H5O_open(H5O_loc_t *loc);
 H5_DLL herr_t H5O_close(H5O_loc_t *loc);
 H5_DLL int H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id);
+H5_DLL int H5O_link_oh(H5F_t *f, int adjust, hid_t dxpl_id, H5O_t *oh, unsigned *oh_flags);
 H5_DLL H5O_t *H5O_protect(H5O_loc_t *loc, hid_t dxpl_id);
 H5_DLL herr_t H5O_unprotect(H5O_loc_t *loc, H5O_t *oh);
 H5_DLL herr_t H5O_touch(H5O_loc_t *loc, hbool_t force, hid_t dxpl_id);
@@ -627,8 +628,8 @@ H5_DLL herr_t H5O_msg_get_crt_index(unsigned type_id, const void *mesg,
     H5O_msg_crt_idx_t *crt_idx);
 H5_DLL herr_t H5O_msg_encode(H5F_t *f, unsigned type_id, hbool_t disable_shared,
     unsigned char *buf, const void *obj);
-H5_DLL void* H5O_msg_decode(H5F_t *f, hid_t dxpl_id, unsigned type_id,
-    const unsigned char *buf);
+H5_DLL void* H5O_msg_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned type_id, const unsigned char *buf);
 H5_DLL herr_t H5O_msg_delete(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
     unsigned type_id, void *mesg);
 
diff --git a/src/H5Orefcount.c b/src/H5Orefcount.c
index b2f02b2..2f00e86 100644
--- a/src/H5Orefcount.c
+++ b/src/H5Orefcount.c
@@ -33,8 +33,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_refcount_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_refcount_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_refcount_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_refcount_copy(const void *_mesg, void *_dest);
 static size_t H5O_refcount_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -90,8 +90,8 @@ H5FL_DEFINE_STATIC(H5O_refcount_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_refcount_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_refcount_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_refcount_t *refcount = NULL;  /* Reference count */
     void        *ret_value;     /* Return value */
diff --git a/src/H5Osdspace.c b/src/H5Osdspace.c
index fe7bf02..23af101 100644
--- a/src/H5Osdspace.c
+++ b/src/H5Osdspace.c
@@ -26,8 +26,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_sdspace_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_sdspace_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_sdspace_encode(H5F_t *f, uint8_t *p, const void *_mesg);
 static void *H5O_sdspace_copy(const void *_mesg, void *_dest);
 static size_t H5O_sdspace_size(const H5F_t *f, const void *_mesg);
@@ -109,8 +109,8 @@ H5FL_ARR_EXTERN(hsize_t);
     within this function using malloc() and is returned to the caller.
 --------------------------------------------------------------------------*/
 static void *
-H5O_sdspace_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_sdspace_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5S_extent_t	*sdim = NULL;/* New extent dimensionality structure */
     void		*ret_value;
diff --git a/src/H5Oshared.c b/src/H5Oshared.c
index 062443a..e22a105 100644
--- a/src/H5Oshared.c
+++ b/src/H5Oshared.c
@@ -107,7 +107,7 @@
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_shared_read(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
+H5O_shared_read(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, unsigned *ioflags,
     const H5O_shared_t *shared, const H5O_msg_class_t *type)
 {
     H5HF_t *fheap = NULL;
@@ -159,7 +159,7 @@ H5O_shared_read(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
             HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "can't read message from fractal heap.")
 
         /* Decode the message */
-        if(NULL == (ret_value = (type->decode)(f, dxpl_id, 0, ioflags, mesg_ptr)))
+        if(NULL == (ret_value = (type->decode)(f, dxpl_id, open_oh, 0, ioflags, mesg_ptr)))
             HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "can't decode shared message.")
     } /* end if */
     else {
@@ -167,12 +167,22 @@ H5O_shared_read(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
 
         HDassert(shared->type == H5O_SHARE_TYPE_COMMITTED);
 
-        /* Get the shared message from an object header */
+        /* Build the object location for the shared message's object header */
         oloc.file = f;
         oloc.addr = shared->u.loc.oh_addr;
         oloc.holding_file = FALSE;
-        if(NULL == (ret_value = H5O_msg_read(&oloc, type->id, NULL, dxpl_id)))
-            HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to read message")
+
+        if(open_oh && oloc.addr == H5O_OH_GET_ADDR(open_oh)) {
+            /* The shared message is in the already opened object header.  This
+             * is possible, for example, if an attribute's datatype is shared in
+             * the same object header the attribute is in.  Read the message
+             * directly. */
+            if(NULL == (ret_value = H5O_msg_read_oh(f, dxpl_id, open_oh, type->id, NULL)))
+                HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to read message")
+        } else
+            /* The shared message is in another object header */
+            if(NULL == (ret_value = H5O_msg_read(&oloc, type->id, NULL, dxpl_id)))
+                HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to read message")
     } /* end else */
 
     /* Mark the message as shared */
@@ -228,7 +238,7 @@ H5O_shared_link_adj(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
         H5O_loc_t oloc;         /* Location for object header where message is stored */
 
         /*
-         * The shared message is stored in some other object header.
+         * The shared message is stored in some object header.
          * The other object header must be in the same file as the
          * new object header. Adjust the reference count on that
          * object header.
@@ -236,13 +246,26 @@ H5O_shared_link_adj(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
         if(shared->file->shared != f->shared)
             HGOTO_ERROR(H5E_LINK, H5E_CANTINIT, FAIL, "interfile hard links are not allowed")
 
-        /* Get the shared message from an object header */
+        /* Build the object location for the shared message's object header */
         oloc.file = f;
         oloc.addr = shared->u.loc.oh_addr;
         oloc.holding_file = FALSE;
 
-        if(H5O_link(&oloc, adjust, dxpl_id) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
+        if(open_oh && oloc.addr == H5O_OH_GET_ADDR(open_oh)) {
+            /* The shared message is in the already opened object header.  This
+             * is possible, for example, if an attribute's datatype is shared in
+             * the same object header the attribute is in.  Adjust the link
+             * count directly. */
+            unsigned oh_flags = H5AC__NO_FLAGS_SET; /* This is used only to satisfy H5O_link_oh */
+
+            if(H5O_link_oh(f, adjust, dxpl_id, open_oh, &oh_flags) < 0)
+                HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
+
+            HDassert(!(oh_flags & H5AC__DELETED_FLAG));
+        } else
+            /* The shared message is in another object header */
+            if(H5O_link(&oloc, adjust, dxpl_id) < 0)
+                HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
     } /* end if */
     else {
         HDassert(shared->type == H5O_SHARE_TYPE_SOHM || shared->type == H5O_SHARE_TYPE_HERE);
@@ -277,7 +300,7 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5O_shared_decode(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
+H5O_shared_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, unsigned *ioflags,
     const uint8_t *buf, const H5O_msg_class_t *type)
 {
     H5O_shared_t sh_mesg;       /* Shared message info */
@@ -344,7 +367,7 @@ H5O_shared_decode(H5F_t *f, hid_t dxpl_id, unsigned *ioflags,
     sh_mesg.msg_type_id = type->id;
 
     /* Retrieve actual message, through decoded shared message info */
-    if(NULL == (ret_value = H5O_shared_read(f, dxpl_id, ioflags, &sh_mesg, type)))
+    if(NULL == (ret_value = H5O_shared_read(f, dxpl_id, open_oh, ioflags, &sh_mesg, type)))
         HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to retrieve native message")
 
 done:
diff --git a/src/H5Oshared.h b/src/H5Oshared.h
index d52cd8f..c0f5cd6 100644
--- a/src/H5Oshared.h
+++ b/src/H5Oshared.h
@@ -48,7 +48,7 @@
  *-------------------------------------------------------------------------
  */
 static H5_inline void *
-H5O_SHARED_DECODE(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
+H5O_SHARED_DECODE(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, unsigned mesg_flags,
     unsigned *ioflags, const uint8_t *p)
 {
     void *ret_value;            /* Return value */
@@ -68,7 +68,7 @@ H5O_SHARED_DECODE(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
     /* Check for shared message */
     if(mesg_flags & H5O_MSG_FLAG_SHARED) {
         /* Retrieve native message info indirectly through shared message */
-        if(NULL == (ret_value = H5O_shared_decode(f, dxpl_id, ioflags, p, H5O_SHARED_TYPE)))
+        if(NULL == (ret_value = H5O_shared_decode(f, dxpl_id, open_oh, ioflags, p, H5O_SHARED_TYPE)))
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "unable to decode shared message")
 
         /* We currently do not support automatically fixing shared messages */
@@ -81,7 +81,7 @@ H5O_SHARED_DECODE(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
     } /* end if */
     else {
         /* Decode native message directly */
-        if(NULL == (ret_value = H5O_SHARED_DECODE_REAL(f, dxpl_id, mesg_flags, ioflags, p)))
+        if(NULL == (ret_value = H5O_SHARED_DECODE_REAL(f, dxpl_id, open_oh, mesg_flags, ioflags, p)))
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "unable to decode native message")
     } /* end else */
 
diff --git a/src/H5Oshmesg.c b/src/H5Oshmesg.c
index 74fe739..51c1c55 100644
--- a/src/H5Oshmesg.c
+++ b/src/H5Oshmesg.c
@@ -28,8 +28,8 @@
 #include "H5Opkg.h"             /* Object headers			*/
 #include "H5MMprivate.h"	/* Memory management			*/
 
-static void  *H5O_shmesg_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void  *H5O_shmesg_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_shmesg_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void  *H5O_shmesg_copy(const void *_mesg, void *_dest);
 static size_t H5O_shmesg_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -76,8 +76,8 @@ const H5O_msg_class_t H5O_MSG_SHMESG[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_shmesg_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_shmesg_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_shmesg_table_t	*mesg;          /* Native message */
     void                *ret_value;     /* Return value */
diff --git a/src/H5Ostab.c b/src/H5Ostab.c
index 9524f43..a93a46d 100644
--- a/src/H5Ostab.c
+++ b/src/H5Ostab.c
@@ -36,8 +36,8 @@
 
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_stab_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
-    unsigned *ioflags, const uint8_t *p);
+static void *H5O_stab_decode(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh,
+    unsigned mesg_flags, unsigned *ioflags, const uint8_t *p);
 static herr_t H5O_stab_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_stab_copy(const void *_mesg, void *_dest);
 static size_t H5O_stab_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
@@ -96,8 +96,8 @@ H5FL_DEFINE_STATIC(H5O_stab_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_stab_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    unsigned UNUSED *ioflags, const uint8_t *p)
+H5O_stab_decode(H5F_t *f, hid_t UNUSED dxpl_id, H5O_t UNUSED *open_oh,
+    unsigned UNUSED mesg_flags, unsigned UNUSED *ioflags, const uint8_t *p)
 {
     H5O_stab_t          *stab = NULL;
     void                *ret_value;     /* Return value */
diff --git a/src/H5S.c b/src/H5S.c
index b7982f0..40134a6 100644
--- a/src/H5S.c
+++ b/src/H5S.c
@@ -1565,7 +1565,7 @@ H5S_decode(const unsigned char *buf)
 
     /* Decode the extent part of dataspace */
     /* (pass mostly bogus file pointer and bogus DXPL) */
-    if((extent = (H5S_extent_t *)H5O_msg_decode(f, H5P_DEFAULT, H5O_SDSPACE_ID, buf))==NULL)
+    if((extent = (H5S_extent_t *)H5O_msg_decode(f, H5P_DEFAULT, NULL, H5O_SDSPACE_ID, buf))==NULL)
 	HGOTO_ERROR(H5E_DATASPACE, H5E_CANTDECODE, NULL, "can't decode object")
     buf += extent_size;
 
diff --git a/src/H5SM.c b/src/H5SM.c
index d942399..c383877 100755
--- a/src/H5SM.c
+++ b/src/H5SM.c
@@ -1402,7 +1402,7 @@ H5SM_delete(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, H5O_shared_t *sh_mesg)
      * master table needs to be unprotected when we do this.
      */
     if(mesg_buf) {
-        if(NULL == (native_mesg = H5O_msg_decode(f, dxpl_id, type_id, (const unsigned char *)mesg_buf)))
+        if(NULL == (native_mesg = H5O_msg_decode(f, dxpl_id, open_oh, type_id, (const unsigned char *)mesg_buf)))
             HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "can't decode shared message.")
 
         if(H5O_msg_delete(f, dxpl_id, open_oh, type_id, native_mesg) < 0)
diff --git a/src/H5T.c b/src/H5T.c
index d6bc1ed..7e978e7 100644
--- a/src/H5T.c
+++ b/src/H5T.c
@@ -2920,7 +2920,7 @@ H5T_decode(const unsigned char *buf)
 	HGOTO_ERROR(H5E_DATATYPE, H5E_VERSION, NULL, "unknown version of encoded datatype")
 
     /* Decode the serialized datatype message */
-    if((ret_value = H5O_msg_decode(f, H5AC_dxpl_id, H5O_DTYPE_ID, buf)) == NULL)
+    if((ret_value = H5O_msg_decode(f, H5AC_dxpl_id, NULL, H5O_DTYPE_ID, buf)) == NULL)
 	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTDECODE, NULL, "can't decode object")
 
 done: