[svn-r13721] Description:

    Add "fail if unknown" and "mark if unknown" flags to object header messages.
This gives the library a clean way to tell older libraries that a message should
not be just ignored if it's unknown, but that other actions should occur.

Tested on:
    Mac OS X/32 10.4.9 (amazon)
    FreeBSD/32 6.2 (duty)
    FreeBSD/64 6.2 (liberty)
    Linux/32 2.6 (chicago)
    Linux/64 2.6 (chicago2)

13 files changed, 398 insertions, 178 deletions

diff --git a/src/H5D.c b/src/H5D.c
index 0677784..776a2ae 100644
--- a/src/H5D.c
+++ b/src/H5D.c
@@ -1228,11 +1228,26 @@ H5D_update_oh_info(H5F_t *file, hid_t dxpl_id, H5D_t *dset)
          HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to update layout")
 
 #ifdef H5O_ENABLE_BOGUS
-    /*
-     * Add a "bogus" message (for error testing).
-     */
-    if(H5O_bogus_oh(file, dxpl_id, oh)) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, NULL, "unable to update 'bogus' message")
+{
+    H5P_genplist_t     *dc_plist;               /* Dataset's creation property list */
+
+    /* Get dataset's property list object */
+    if(NULL == (dc_plist = H5I_object(dset->shared->dcpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "can't get dataset creation property list")
+
+    /* Check whether to add a "bogus" message */
+    if(H5P_exist_plist(dc_plist, H5O_BOGUS_MSG_FLAGS_NAME) > 0) {
+        uint8_t bogus_flags = 0;        /* Flags for creating "bogus" message */
+
+        /* Retrieve "bogus" message flags */
+        if(H5P_get(dc_plist, H5O_BOGUS_MSG_FLAGS_NAME, &bogus_flags) < 0)
+            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get bogus message options")
+
+        /* Add a "bogus" message (for error testing). */
+        if(H5O_bogus_oh(file, dxpl_id, oh, (unsigned)bogus_flags) < 0)
+            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create 'bogus' message")
+    } /* end if */
+}
 #endif /* H5O_ENABLE_BOGUS */
 
     /* Add a modification time message. */
diff --git a/src/H5O.c b/src/H5O.c
index 2bb7505..b529682 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -104,6 +104,7 @@ const H5O_msg_class_t *const H5O_msg_class_g[] = {
     H5O_MSG_DRVINFO,		/*0x0014 Driver info settings		*/
     H5O_MSG_AINFO,		/*0x0015 Attribute information		*/
     H5O_MSG_REFCOUNT,		/*0x0016 Object's ref. count		*/
+    H5O_MSG_UNKNOWN,		/*0x0017 Placeholder for unknown message */
 };
 
 /* Header object ID to class mapping */
@@ -1315,12 +1316,12 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, H5O_t *oh)
+H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned mesg_flags)
 {
-    int	idx;
-    herr_t      ret_value = SUCCEED;       /* Return value */
+    unsigned	idx;                    /* Local index variable */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
-    FUNC_ENTER(H5O_bogus_oh, FAIL)
+    FUNC_ENTER_NOAPI(H5O_bogus_oh, FAIL)
 
     HDassert(f);
     HDassert(oh);
@@ -1333,7 +1334,6 @@ H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, H5O_t *oh)
     /* Create a new message */
     if(idx == oh->nmesgs) {
         H5O_bogus_t *bogus;             /* Pointer to the bogus information */
-        unsigned mesg_flags = 0;        /* Flags for message in object header */
 
         /* Allocate the native message in memory */
 	if(NULL == (bogus = H5MM_malloc(sizeof(H5O_bogus_t))))
@@ -1349,65 +1349,17 @@ H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, H5O_t *oh)
         /* Point to "bogus" information (take it over) */
 	oh->mesg[idx].native = bogus;
 
-        /* Mark the message and object header as dirty */
+        /* Set the appropriate flags for the message */
         oh->mesg[idx].flags = mesg_flags;
+
+        /* Mark the message and object header as dirty */
         oh->mesg[idx].dirty = TRUE;
-        oh->dirty = TRUE;
+        oh->cache_info.is_dirty = TRUE;
     } /* end if */
 
 done:
-    FUNC_LEAVE(ret_value)
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_bogus_oh() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_bogus
- *
- * Purpose:	Create a "bogus" message in an object.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *              <koziol@ncsa.uiuc.edu>
- *              Tuesday, January 21, 2003
- *
- *-------------------------------------------------------------------------
- */
-herr_t
-H5O_bogus(H5O_loc_t *loc, hid_t dxpl_id)
-{
-    H5O_t	*oh = NULL;
-    unsigned	oh_flags = H5AC__NO_FLAGS_SET;
-    herr_t	ret_value = SUCCEED;
-
-    FUNC_ENTER(H5O_bogus, FAIL)
-
-    /* check args */
-    HDassert(loc);
-    HDassert(loc->file);
-    HDassert(H5F_addr_defined(loc->addr));
-
-    /* Verify write access to the file */
-    if(0 == (H5F_INTENT(loc->file) & H5F_ACC_RDWR))
-	HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "no write intent on file")
-
-    /* Get the object header */
-    if(NULL == (oh = H5AC_protect(loc->file, dxpl_id, H5AC_OHDR, loc->addr, NULL, NULL, H5AC_WRITE)))
-	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header")
-
-    /* Create the "bogus" message */
-    if(H5O_bogus_oh(ent->file, dxpl_id, oh) < 0)
-	HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to update object 'bogus' message")
-
-    /* Mark object header as changed */
-    oh_flags |= H5AC__DIRTIED_FLAG;
-
-done:
-    if(oh && H5AC_unprotect(ent->file, dxpl_id, H5AC_OHDR, ent->header, oh, oh_flags) < 0)
-	HDONE_ERROR(H5E_OHDR, H5E_PROTECT, FAIL, "unable to release object header")
-
-    FUNC_LEAVE(ret_value)
-} /* end H5O_bogus() */
 #endif /* H5O_ENABLE_BOGUS */
 
 
@@ -1982,7 +1934,7 @@ H5O_get_info(H5O_loc_t *oloc, H5O_info_t *oinfo, hid_t dxpl_id)
     } /* end for */
 
     /* Sanity check that all the bytes are accounted for */
-    HDassert(oinfo->hdr.space.total == (oinfo->hdr.space.free + oinfo->hdr.space.meta + oinfo->hdr.space.mesg + oh->skipped_mesg_size));
+    HDassert(oinfo->hdr.space.total == (oinfo->hdr.space.free + oinfo->hdr.space.meta + oinfo->hdr.space.mesg));
 
 done:
     if(oh && H5AC_unprotect(oloc->file, dxpl_id, H5AC_OHDR, oloc->addr, oh, H5AC__NO_FLAGS_SET) < 0)
diff --git a/src/H5Obogus.c b/src/H5Obogus.c
index 488758b..4def755 100644
--- a/src/H5Obogus.c
+++ b/src/H5Obogus.c
@@ -86,37 +86,37 @@ const H5O_msg_class_t H5O_MSG_BOGUS[1] = {{
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_bogus_decode(H5F_t UNUSED *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
+H5O_bogus_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
     const uint8_t *p)
 {
     H5O_bogus_t *mesg = NULL;
     void *ret_value;            /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_bogus_decode);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_bogus_decode)
 
     /* check args */
-    assert(f);
-    assert(p);
+    HDassert(f);
+    HDassert(p);
 
     /* Allocate the bogus message */
-    if (NULL==(mesg = H5MM_calloc(sizeof(H5O_bogus_t))))
-	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
+    if(NULL == (mesg = H5MM_calloc(sizeof(H5O_bogus_t))))
+	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* decode */
     UINT32DECODE(p, mesg->u);
 
     /* Validate the bogus info */
-    if(mesg->u!=H5O_BOGUS_VALUE)
-	HGOTO_ERROR (H5E_OHDR, H5E_BADVALUE, NULL, "invalid bogus value :-)");
+    if(mesg->u != H5O_BOGUS_VALUE)
+	HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, NULL, "invalid bogus value :-)")
 
     /* Set return value */
-    ret_value=mesg;
+    ret_value = mesg;
 
 done:
-    if(ret_value==NULL && mesg!=NULL)
+    if(ret_value == NULL && mesg != NULL)
         H5MM_xfree(mesg);
 
-    FUNC_LEAVE_NOAPI(ret_value);
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_bogus_decode() */
 
 
@@ -136,17 +136,17 @@ done:
 static herr_t
 H5O_bogus_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void UNUSED *mesg)
 {
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_encode);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_encode)
 
     /* check args */
-    assert(f);
-    assert(p);
-    assert(mesg);
+    HDassert(f);
+    HDassert(p);
+    HDassert(mesg);
 
     /* encode */
     UINT32ENCODE(p, H5O_BOGUS_VALUE);
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
+    FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_bogus_encode() */
 
 
@@ -171,12 +171,9 @@ H5O_bogus_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, con
 static size_t
 H5O_bogus_size(const H5F_t UNUSED *f, hbool_t UNUSED disable_shared, const void UNUSED *mesg)
 {
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_size);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_size)
 
-    /* check args */
-    assert(f);
-
-    FUNC_LEAVE_NOAPI(4);
+    FUNC_LEAVE_NOAPI(4)
 } /* end H5O_bogus_size() */
 
 
@@ -201,20 +198,19 @@ H5O_bogus_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE *
 {
     const H5O_bogus_t	*mesg = (const H5O_bogus_t *)_mesg;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_name_debug);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_debug)
 
     /* check args */
-    assert(f);
-    assert(mesg);
-    assert(stream);
-    assert(indent >= 0);
-    assert(fwidth >= 0);
+    HDassert(f);
+    HDassert(mesg);
+    HDassert(stream);
+    HDassert(indent >= 0);
+    HDassert(fwidth >= 0);
 
-    fprintf(stream, "%*s%-*s `%u'\n", indent, "", fwidth,
+    HDfprintf(stream, "%*s%-*s `%u'\n", indent, "", fwidth,
             "Bogus Value:", mesg->u);
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_bogus_debug() */
 #endif /* H5O_ENABLE_BOGUS */
 
-
diff --git a/src/H5Ocache.c b/src/H5Ocache.c
index 75f9d69..d574fe8 100644
--- a/src/H5Ocache.c
+++ b/src/H5Ocache.c
@@ -30,6 +30,7 @@
 
 #define H5O_PACKAGE		/*suppress error about including H5Opkg	  */
 
+
 /***********/
 /* Headers */
 /***********/
@@ -38,6 +39,7 @@
 #include "H5FLprivate.h"	/* Free lists                           */
 #include "H5Opkg.h"             /* Object headers			*/
 
+
 /****************/
 /* Local Macros */
 /****************/
@@ -80,6 +82,9 @@ static herr_t H5O_size(const H5F_t *f, const H5O_t *oh, size_t *size_ptr);
 /* Library Private Variables */
 /*****************************/
 
+/* Declare external the free list for H5O_unknown_t's */
+H5FL_EXTERN(H5O_unknown_t);
+
 
 /*******************/
 /* Local Variables */
@@ -126,15 +131,22 @@ H5O_flush_msgs(H5F_t *f, H5O_t *oh)
     for(u = 0, curr_msg = &oh->mesg[0]; u < oh->nmesgs; u++, curr_msg++) {
         if(curr_msg->dirty) {
             uint8_t	*p;             /* Temporary pointer to encode with */
+            unsigned    msg_id;         /* ID for message */
 
             /* Point into message's chunk's image */
             p = curr_msg->raw - H5O_SIZEOF_MSGHDR_OH(oh);
 
+            /* Retrieve actual message ID, for unknown messages */
+            if(curr_msg->type == H5O_MSG_UNKNOWN)
+                msg_id = *(H5O_unknown_t *)(curr_msg->native);
+            else
+                msg_id = (uint8_t)curr_msg->type->id;
+
             /* Encode the message prefix */
             if(oh->version == H5O_VERSION_1)
-                UINT16ENCODE(p, curr_msg->type->id)
+                UINT16ENCODE(p, msg_id)
             else
-                *p++ = (uint8_t)curr_msg->type->id;
+                *p++ = (uint8_t)msg_id;
             HDassert(curr_msg->raw_size < H5O_MESG_MAX_SIZE);
             UINT16ENCODE(p, curr_msg->raw_size);
             *p++ = curr_msg->flags;
@@ -155,12 +167,16 @@ H5O_flush_msgs(H5F_t *f, H5O_t *oh)
 
 #ifndef NDEBUG
             /* Make certain that null messages aren't in chunks w/gaps */
-            if(H5O_NULL_ID == curr_msg->type->id)
+            if(H5O_NULL_ID == msg_id)
                 HDassert(oh->chunk[curr_msg->chunkno].gap == 0);
+
+            /* Unknown messages should always have a native pointer */
+            if(curr_msg->type == H5O_MSG_UNKNOWN)
+                HDassert(curr_msg->native);
 #endif /* NDEBUG */
 
-            /* Encode the message itself */
-            if(curr_msg->native) {
+            /* Encode the message itself, if it's not an "unknown" message */
+            if(curr_msg->native && curr_msg->type != H5O_MSG_UNKNOWN) {
                 /*
                  * Encode the message.  If the message is shared then we
                  * encode a Shared Object message instead of the object
@@ -226,7 +242,6 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
     size_t	prefix_size;    /* Size of object header prefix */
     unsigned	nmesgs;         /* Total # of messages in this object header */
     unsigned	curmesg = 0;    /* Current message being decoded in object header */
-    unsigned    skipped_msgs = 0;       /* Number of unknown messages skipped */
     unsigned    merged_null_msgs = 0;   /* Number of null messages merged together */
     haddr_t	chunk_addr;     /* Address of first chunk */
     size_t	chunk_size;     /* Size of first chunk */
@@ -474,12 +489,24 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
             else
                 id = *p++;
 
+            /* Check for unknown message ID getting encoded in file */
+            if(id == H5O_UNKNOWN_ID)
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "'unknown' message ID encoded in file?!?")
+
             /* Message size */
 	    UINT16DECODE(p, mesg_size);
 	    HDassert(mesg_size == H5O_ALIGN_OH(oh, mesg_size));
 
             /* Message flags */
 	    flags = *p++;
+            if(flags & ~H5O_MSG_FLAG_BITS)
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "unknown flag for message")
+            if((flags & H5O_MSG_FLAG_SHARED) && (flags & H5O_MSG_FLAG_DONTSHARE))
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "bad flag combination for message")
+            if((flags & H5O_MSG_FLAG_WAS_UNKNOWN) && (flags & H5O_MSG_FLAG_FAIL_IF_UNKNOWN))
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "bad flag combination for message")
+            if((flags & H5O_MSG_FLAG_WAS_UNKNOWN) && !(flags & H5O_MSG_FLAG_MARK_IF_UNKNOWN))
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "bad flag combination for message")
 
             /* Reserved bytes/creation index */
             if(oh->version == H5O_VERSION_1)
@@ -496,51 +523,89 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
 	    if(p + mesg_size > eom_ptr)
 		HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "corrupt object header")
 
-            /* Skip header messages we don't know about */
-            /* (Usually from future versions of the library) */
-	    if(id >= NELMTS(H5O_msg_class_g) || NULL == H5O_msg_class_g[id]) {
-                /* Increment the size of the message skipped over (for later sanity checking) */
-                oh->skipped_mesg_size += H5O_SIZEOF_MSGHDR_OH(oh) + mesg_size;
-
-                /* Increment skipped messages counter */
-                skipped_msgs++;
-            } /* end if */
-            else {
 #ifndef NDEBUG
-                /* Increment count of null messages */
-                if(H5O_NULL_ID == id)
-                    nullcnt++;
+            /* Increment count of null messages */
+            if(H5O_NULL_ID == id)
+                nullcnt++;
 #endif /* NDEBUG */
 
-                /* Check for combining two adjacent 'null' messages */
-                if((H5F_get_intent(f) & H5F_ACC_RDWR) &&
-                        H5O_NULL_ID == id && oh->nmesgs > 0 &&
-                        H5O_NULL_ID == oh->mesg[oh->nmesgs - 1].type->id &&
-                        oh->mesg[oh->nmesgs - 1].chunkno == chunkno) {
-
-                    /* Combine adjacent null messages */
-                    mesgno = oh->nmesgs - 1;
-                    oh->mesg[mesgno].raw_size += H5O_SIZEOF_MSGHDR_OH(oh) + mesg_size;
-                    oh->mesg[mesgno].dirty = TRUE;
-                    merged_null_msgs++;
+            /* Check for combining two adjacent 'null' messages */
+            if((H5F_get_intent(f) & H5F_ACC_RDWR) &&
+                    H5O_NULL_ID == id && oh->nmesgs > 0 &&
+                    H5O_NULL_ID == oh->mesg[oh->nmesgs - 1].type->id &&
+                    oh->mesg[oh->nmesgs - 1].chunkno == chunkno) {
+
+                /* Combine adjacent null messages */
+                mesgno = oh->nmesgs - 1;
+                oh->mesg[mesgno].raw_size += H5O_SIZEOF_MSGHDR_OH(oh) + mesg_size;
+                oh->mesg[mesgno].dirty = TRUE;
+                merged_null_msgs++;
+            } /* end if */
+            else {
+                /* Check if we need to extend message table to hold the new message */
+                if(oh->nmesgs >= oh->alloc_nmesgs)
+                    if(H5O_alloc_msgs(oh, (size_t)1) < 0)
+                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate more space for messages")
+
+                /* Get index for message */
+                mesgno = oh->nmesgs++;
+
+                /* Initialize information about message */
+                oh->mesg[mesgno].dirty = FALSE;
+                oh->mesg[mesgno].flags = flags;
+                oh->mesg[mesgno].crt_idx = crt_idx;
+                oh->mesg[mesgno].native = NULL;
+                oh->mesg[mesgno].raw = (uint8_t *)p;        /* Casting away const OK - QAK */
+                oh->mesg[mesgno].raw_size = mesg_size;
+                oh->mesg[mesgno].chunkno = chunkno;
+
+                /* Point unknown messages at 'unknown' message class */
+                /* (Usually from future versions of the library) */
+                if(id >= NELMTS(H5O_msg_class_g) || NULL == H5O_msg_class_g[id]) {
+                    H5O_unknown_t *unknown;     /* Pointer to "unknown" message info */
+
+                    /* Allocate "unknown" message info */
+                    if(NULL == (unknown = H5FL_MALLOC(H5O_unknown_t)))
+                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
+
+                    /* Save the original message type ID */
+                    *unknown = id;
+
+                    /* Save 'native' form of continuation message */
+                    oh->mesg[mesgno].native = unknown;
+
+                    /* Set message to "unknown" class */
+                    oh->mesg[mesgno].type = H5O_msg_class_g[H5O_UNKNOWN_ID];
+
+                    /* Check for "fail if unknown" message flag */
+                    if(flags & H5O_MSG_FLAG_FAIL_IF_UNKNOWN)
+                        HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, NULL, "unknown message with 'fail if unknown' flag found")
+                    /* Check for "mark if unknown" message flag, etc. */
+                    else if((flags & H5O_MSG_FLAG_MARK_IF_UNKNOWN) &&
+                            !(flags & H5O_MSG_FLAG_WAS_UNKNOWN) &&
+                            (H5F_get_intent(f) & H5F_ACC_RDWR)) {
+
+                        /* Mark the message as "unknown" */
+                        /* This is a bit aggressive, since the application may
+                         * never change anything about the object (metadata or
+                         * raw data), but we can sort out the finer details
+                         * when/if we start using the flag - QAK
+                         */
+                        /* Also, it's possible that this functionality may not
+                         * get invoked if the object header is brought into
+                         * the metadata cache in some other "weird" way, like
+                         * using H5Ocopy() - QAK
+                         */
+                        oh->mesg[mesgno].flags |= H5O_MSG_FLAG_WAS_UNKNOWN;
+
+                        /* Mark the message and object header as dirty */
+                        oh->mesg[mesgno].dirty = TRUE;
+                        oh->cache_info.is_dirty = TRUE;
+                    } /* end if */
                 } /* end if */
-                else {
-                    /* Check if we need to extend message table to hold the new message */
-                    if(oh->nmesgs >= oh->alloc_nmesgs)
-                        if(H5O_alloc_msgs(oh, (size_t)1) < 0)
-                            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate more space for messages")
-
-                    /* Record information about message */
-                    mesgno = oh->nmesgs++;
+                else
+                    /* Set message class for "known" messages */
                     oh->mesg[mesgno].type = H5O_msg_class_g[id];
-                    oh->mesg[mesgno].dirty = FALSE;
-                    oh->mesg[mesgno].flags = flags;
-                    oh->mesg[mesgno].crt_idx = crt_idx;
-                    oh->mesg[mesgno].native = NULL;
-                    oh->mesg[mesgno].raw = (uint8_t *)p;        /* Casting away const OK - QAK */
-                    oh->mesg[mesgno].raw_size = mesg_size;
-                    oh->mesg[mesgno].chunkno = chunkno;
-                } /* end else */
             } /* end else */
 
             /* Advance decode pointer past message */
@@ -632,7 +697,7 @@ H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED * _udata1,
 
     /* Sanity check for the correct # of messages in object header */
     if(oh->version == H5O_VERSION_1)
-        if((oh->nmesgs + skipped_msgs + merged_null_msgs) != nmesgs)
+        if((oh->nmesgs + merged_null_msgs) != nmesgs)
             HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "corrupt object header - too few messages")
 
 #ifdef H5O_DEBUG
@@ -645,7 +710,7 @@ H5O_assert(oh);
 done:
     /* Release the [possibly partially initialized] object header on errors */
     if(!ret_value && oh)
-        if(H5O_dest(f,oh) < 0)
+        if(H5O_dest(f, oh) < 0)
 	    HDONE_ERROR(H5E_OHDR, H5E_CANTFREE, NULL, "unable to destroy object header data")
 
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5Ocopy.c b/src/H5Ocopy.c
index 5549cd6..71d4c0a 100644
--- a/src/H5Ocopy.c
+++ b/src/H5Ocopy.c
@@ -341,7 +341,6 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
     /* Initialize header information */
     oh_dst->version = oh_src->version;
     oh_dst->flags = oh_src->flags;
-    oh_dst->skipped_mesg_size = oh_src->skipped_mesg_size;
     oh_dst->link_msgs_seen = oh_src->link_msgs_seen;
     oh_dst->attr_msgs_seen = oh_src->attr_msgs_seen;
     oh_dst->sizeof_size = H5F_SIZEOF_SIZE(oloc_dst->file);
diff --git a/src/H5Odbg.c b/src/H5Odbg.c
index 108ac81..c73360f 100644
--- a/src/H5Odbg.c
+++ b/src/H5Odbg.c
@@ -207,7 +207,7 @@ H5O_assert(const H5O_t *oh)
     HDassert(oh->nchunks == (cont_msgs_found + 1));
 
     /* Sanity check that all the bytes are accounted for */
-    HDassert(hdr_size == (free_space + meta_space + mesg_space + oh->skipped_mesg_size));
+    HDassert(hdr_size == (free_space + meta_space + mesg_space));
 
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_assert() */
@@ -427,31 +427,57 @@ H5O_debug_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, haddr_t addr, FILE *stream, i
 		  (unsigned) (oh->mesg[i].type->id),
 		  oh->mesg[i].type->name,
 		  sequence[oh->mesg[i].type->id]++);
-	HDfprintf(stream, "%*s%-*s %t\n", indent+3, "", MAX (0, fwidth-3),
+	HDfprintf(stream, "%*s%-*s %t\n", indent + 3, "", MAX (0, fwidth - 3),
 		   "Dirty:",
 		   oh->mesg[i].dirty);
-	HDfprintf(stream, "%*s%-*s %s\n", indent+3, "", MAX (0, fwidth-3),
-		   "Shared:",
-		   (oh->mesg[i].flags & H5O_MSG_FLAG_SHARED) ? "Yes" : "No");
-	HDfprintf(stream, "%*s%-*s %s\n", indent + 3, "", MAX(0, fwidth - 3),
-		  "Constant:",
-		  (oh->mesg[i].flags & H5O_MSG_FLAG_CONSTANT) ? "Yes" : "No");
-	if(oh->mesg[i].flags & ~H5O_MSG_FLAG_BITS)
-	    HDfprintf(stream, "%*s%-*s 0x%02x\n", indent+3,"",MAX(0,fwidth-3),
-		       "*** ADDITIONAL UNKNOWN FLAGS --->",
-		       oh->mesg[i].flags & ~H5O_MSG_FLAG_BITS);
-	HDfprintf(stream, "%*s%-*s %Zu bytes\n", indent+3, "", MAX(0,fwidth-3),
-		  "Raw size in obj header:",
-		  oh->mesg[i].raw_size);
+        HDfprintf(stream, "%*s%-*s ", indent + 3, "", MAX (0, fwidth - 3),
+                   "Message flags:");
+	if(oh->mesg[i].flags) {
+            hbool_t flag_printed = FALSE;
+
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_SHARED) {
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "S");
+                flag_printed = TRUE;
+            } /* end if */
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_CONSTANT) {
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "C");
+                flag_printed = TRUE;
+            } /* end if */
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_DONTSHARE) {
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "DS");
+                flag_printed = TRUE;
+            } /* end if */
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_FAIL_IF_UNKNOWN) {
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "FIU");
+                flag_printed = TRUE;
+            } /* end if */
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_MARK_IF_UNKNOWN) {
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "MIU");
+                flag_printed = TRUE;
+            } /* end if */
+            if(oh->mesg[i].flags & H5O_MSG_FLAG_WAS_UNKNOWN) {
+                HDassert(oh->mesg[i].flags & H5O_MSG_FLAG_MARK_IF_UNKNOWN);
+                HDfprintf(stream, "%s%s", (flag_printed ? ", " : "<"), "WU");
+                flag_printed = TRUE;
+            } /* end if */
+            HDfprintf(stream, ">\n");
+            if(oh->mesg[i].flags & ~H5O_MSG_FLAG_BITS)
+                HDfprintf(stream, "%*s%-*s 0x%02x\n", indent + 3,"", MAX(0, fwidth - 3),
+                           "*** ADDITIONAL UNKNOWN FLAGS --->",
+                           oh->mesg[i].flags & ~H5O_MSG_FLAG_BITS);
+        } /* end if */
+        else
+            HDfprintf(stream, "<none>\n");
 	HDfprintf(stream, "%*s%-*s %u\n", indent + 3, "", MAX(0, fwidth - 3),
 		  "Chunk number:",
 		  oh->mesg[i].chunkno);
 	chunkno = oh->mesg[i].chunkno;
 	if(chunkno >= oh->nchunks)
 	    HDfprintf(stream, "*** BAD CHUNK NUMBER\n");
-	HDfprintf(stream, "%*s%-*s %Zu\n", indent + 3, "", MAX(0, fwidth - 3),
-		  "Raw data offset in chunk:",
-		  (size_t)(oh->mesg[i].raw - oh->chunk[chunkno].image));
+	HDfprintf(stream, "%*s%-*s (%Zu, %Zu) bytes\n", indent + 3, "", MAX(0, fwidth - 3),
+		  "Raw message data (offset, size) in chunk:",
+		  (size_t)(oh->mesg[i].raw - oh->chunk[chunkno].image),
+		  oh->mesg[i].raw_size);
 
 	/* check the size */
 	if((oh->mesg[i].raw + oh->mesg[i].raw_size >
diff --git a/src/H5Omessage.c b/src/H5Omessage.c
index a8b332b..a6e13b0 100644
--- a/src/H5Omessage.c
+++ b/src/H5Omessage.c
@@ -340,7 +340,7 @@ H5O_msg_write_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, const H5O_msg_class_t *ty
 
     /* Locate message of correct type */
     for(idx = 0, idx_msg = &oh->mesg[0]; idx < oh->nmesgs; idx++, idx_msg++)
-	if(type->id == idx_msg->type->id)
+	if(type == idx_msg->type)
             break;
     if(idx == oh->nmesgs)
         HGOTO_ERROR(H5E_OHDR, H5E_NOTFOUND, FAIL, "message type not found")
@@ -482,7 +482,7 @@ H5O_msg_read_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned type_id,
 
     /* Scan through the messages looking for the right one */
     for(idx = 0; idx < oh->nmesgs; idx++)
-	if(type_id == oh->mesg[idx].type->id)
+	if(type == oh->mesg[idx].type)
             break;
     if(idx == oh->nmesgs)
         HGOTO_ERROR(H5E_OHDR, H5E_NOTFOUND, NULL, "message type not found")
@@ -879,7 +879,7 @@ H5O_msg_exists_oh(const H5O_t *oh, unsigned type_id)
 
     /* Scan through the messages looking for the right one */
     for(u = 0; u < oh->nmesgs; u++)
-	if(type->id == oh->mesg[u].type->id)
+	if(type == oh->mesg[u].type)
             HGOTO_DONE(TRUE)
 
 done:
@@ -1242,7 +1242,7 @@ H5O_msg_iterate_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
 
     /* Iterate over messages */
     for(sequence = 0, idx = 0, idx_msg = &oh->mesg[0]; idx < oh->nmesgs && !ret_value; idx++, idx_msg++) {
-	if(type->id == idx_msg->type->id) {
+	if(type == idx_msg->type) {
             /* Decode the message if necessary.  */
             H5O_LOAD_NATIVE(f, dxpl_id, idx_msg, FAIL)
 
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index 067e36c..a999638 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -30,7 +30,7 @@
 #define H5O_NMESGS	8 		/*initial number of messages	     */
 #define H5O_NCHUNKS	2		/*initial number of chunks	     */
 #define H5O_MIN_SIZE	22		/* Min. obj header data size (must be big enough for a message prefix and a continuation message) */
-#define H5O_MSG_TYPES   23              /* # of types of messages            */
+#define H5O_MSG_TYPES   24              /* # of types of messages            */
 #define H5O_MAX_CRT_ORDER_IDX 65535     /* Max. creation order index value   */
 
 /* Versions of object header structure */
@@ -265,7 +265,6 @@ struct H5O_t {
     size_t	nmesgs;			/*number of messages		     */
     size_t	alloc_nmesgs;		/*number of message slots	     */
     H5O_mesg_t	*mesg;			/*array of messages		     */
-    size_t      skipped_mesg_size;      /*size of skipped messages (for sanity checking) */
     size_t      link_msgs_seen;         /* # of link messages seen when loading header */
     size_t      attr_msgs_seen;         /* # of attribute messages seen when loading header */
 
@@ -440,6 +439,9 @@ H5_DLLVAR const H5O_msg_class_t H5O_MSG_AINFO[1];
 /* Reference Count Message. (0x0016) */
 H5_DLLVAR const H5O_msg_class_t H5O_MSG_REFCOUNT[1];
 
+/* Placeholder for unknown message. (0x0017) */
+H5_DLLVAR const H5O_msg_class_t H5O_MSG_UNKNOWN[1];
+
 
 /*
  * Object header "object" types
@@ -523,6 +525,7 @@ H5_DLL htri_t H5O_is_attr_empty_test(hid_t oid);
 H5_DLL htri_t H5O_is_attr_dense_test(hid_t oid);
 H5_DLL herr_t H5O_num_attrs_test(hid_t oid, hsize_t *nattrs);
 H5_DLL herr_t H5O_attr_dense_info_test(hid_t oid, hsize_t *name_count, hsize_t *corder_count);
+H5_DLL herr_t H5O_check_msg_marked_test(hid_t oid, hbool_t flag_val);
 #endif /* H5O_TESTING */
 
 /* Object header debugging routines */
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index f904c4c..0689838 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -71,8 +71,9 @@ typedef struct H5O_t H5O_t;
 #define H5O_MSG_FLAG_SHARED	0x02u
 #define H5O_MSG_FLAG_DONTSHARE	0x04u
 #define H5O_MSG_FLAG_FAIL_IF_UNKNOWN 0x08u
-#define H5O_MSG_FLAG_CURRENT 0x10u
-#define H5O_MSG_FLAG_BITS	(H5O_MSG_FLAG_CONSTANT|H5O_MSG_FLAG_SHARED|H5O_MSG_FLAG_DONTSHARE)
+#define H5O_MSG_FLAG_MARK_IF_UNKNOWN 0x10u
+#define H5O_MSG_FLAG_WAS_UNKNOWN 0x20u
+#define H5O_MSG_FLAG_BITS	(H5O_MSG_FLAG_CONSTANT|H5O_MSG_FLAG_SHARED|H5O_MSG_FLAG_DONTSHARE|H5O_MSG_FLAG_FAIL_IF_UNKNOWN|H5O_MSG_FLAG_MARK_IF_UNKNOWN|H5O_MSG_FLAG_WAS_UNKNOWN)
 
 /* Flags for updating messages */
 #define H5O_UPDATE_TIME         0x01u
@@ -84,6 +85,10 @@ typedef struct H5O_t H5O_t;
 #define H5O_CRT_ATTR_MAX_COMPACT_NAME	"max compact attr"      /* Max. # of attributes to store compactly */
 #define H5O_CRT_ATTR_MIN_DENSE_NAME	"min dense attr"	/* Min. # of attributes to store densely */
 #define H5O_CRT_OHDR_FLAGS_NAME		"object header flags"	/* Object header flags */
+#ifdef H5O_ENABLE_BOGUS
+#define H5O_BOGUS_MSG_FLAGS_NAME        "bogus msg flags"       /* Flags for 'bogus' message */
+#define H5O_BOGUS_MSG_FLAGS_SIZE        sizeof(uint8_t)
+#endif /* H5O_ENABLE_BOGUS */
 
 /* ========= Object Copy properties ============ */
 #define H5O_CPY_OPTION_NAME 		"copy object"           /* Copy options */
@@ -136,6 +141,8 @@ typedef struct H5O_copy_t {
 #define H5O_DRVINFO_ID  0x0014          /* Driver info message.  */
 #define H5O_AINFO_ID    0x0015          /* Attribute info message.  */
 #define H5O_REFCOUNT_ID 0x0016          /* Reference count message.  */
+#define H5O_UNKNOWN_ID  0x0017          /* Placeholder message ID for unknown message.  */
+                                        /* (this should never exist in a file) */
 
 
 /* Shared object message flags.
@@ -432,10 +439,15 @@ typedef struct H5O_ainfo_t {
 
 /*
  * Reference Count Message.
- * (Contains # of links to object, if >1)
  * (Data structure in memory)
  */
-typedef uint32_t H5O_refcount_t;
+typedef uint32_t H5O_refcount_t;        /* Contains # of links to object, if >1 */
+
+/*
+ * "Unknown" Message.
+ * (Data structure in memory)
+ */
+typedef unsigned H5O_unknown_t;         /* Original message type ID */
 
 
 /* Typedef for iteration operations */
@@ -465,8 +477,7 @@ H5_DLL herr_t H5O_touch(H5O_loc_t *loc, hbool_t force, hid_t dxpl_id);
 H5_DLL herr_t H5O_touch_oh(H5F_t *f, hid_t dxpl_id, struct H5O_t *oh,
     hbool_t force);
 #ifdef H5O_ENABLE_BOGUS
-H5_DLL herr_t H5O_bogus(H5O_loc_t *loc, hid_t dxpl_id);
-H5_DLL herr_t H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, struct H5O_t *oh);
+H5_DLL herr_t H5O_bogus_oh(H5F_t *f, hid_t dxpl_id, struct H5O_t *oh, unsigned mesg_flags);
 #endif /* H5O_ENABLE_BOGUS */
 H5_DLL herr_t H5O_delete(H5F_t *f, hid_t dxpl_id, haddr_t addr);
 H5_DLL herr_t H5O_get_info(H5O_loc_t *oloc, H5O_info_t *oinfo, hid_t dxpl_id);
diff --git a/src/H5Otest.c b/src/H5Otest.c
index 41c79ef..359c312 100644
--- a/src/H5Otest.c
+++ b/src/H5Otest.c
@@ -16,7 +16,7 @@
 /* Programmer:  Quincey Koziol <koziol@hdfgroup.org>
  *              Monday, December 4, 2006
  *
- * Purpose:	Attribute testing functions.
+ * Purpose:	Object header testing functions.
  */
 
 /****************/
@@ -357,3 +357,66 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 }   /* H5O_attr_dense_info_test() */
 
+
+/*--------------------------------------------------------------------------
+ NAME
+    H5O_check_msg_marked_test
+ PURPOSE
+    Check if an unknown message with the "mark if unknown" flag actually gets
+    marked.
+ USAGE
+    herr_t H5O_check_msg_marked_test(oid, flag_val)
+        hid_t oid;              IN: Object to check
+        hbool_t flag_val;       IN: Desired flag value
+ RETURNS
+    Non-negative on success, negative on failure
+ DESCRIPTION
+    Locates the "unknown" message and checks that the "was unknown" flag is set
+    correctly.
+ GLOBAL VARIABLES
+ COMMENTS, BUGS, ASSUMPTIONS
+    DO NOT USE THIS FUNCTION FOR ANYTHING EXCEPT TESTING
+ EXAMPLES
+ REVISION LOG
+--------------------------------------------------------------------------*/
+herr_t
+H5O_check_msg_marked_test(hid_t oid, hbool_t flag_val)
+{
+    H5O_t *oh = NULL;           /* Object header */
+    H5O_loc_t *oloc;            /* Pointer to object's location */
+    H5O_mesg_t *idx_msg;        /* Pointer to message */
+    unsigned idx;               /* Index of message */
+    herr_t ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_NOAPI(H5O_check_msg_marked_test, FAIL)
+
+    /* Get object location for object */
+    if(NULL == (oloc = H5O_get_loc(oid)))
+        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "object not found")
+
+    /* Get the object header */
+    if(NULL == (oh = H5AC_protect(oloc->file, H5AC_ind_dxpl_id, H5AC_OHDR, oloc->addr, NULL, NULL, H5AC_READ)))
+	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header")
+
+    /* Locate "unknown" message  */
+    for(idx = 0, idx_msg = &oh->mesg[0]; idx < oh->nmesgs; idx++, idx_msg++)
+	if(idx_msg->type->id == H5O_UNKNOWN_ID) {
+            /* Check for "unknown" message having the correct flags */
+            if(((idx_msg->flags & H5O_MSG_FLAG_WAS_UNKNOWN) > 0) != flag_val)
+                HGOTO_ERROR(H5E_OHDR, H5E_BADVALUE, FAIL, "'unknown' message has incorrect 'was unknown' flag value")
+
+            /* Break out of loop, to indicate that the "unknown" message was found */
+            break;
+        } /* end if */
+
+    /* Check for not finding an "unknown" message */
+    if(idx == oh->nmesgs)
+        HGOTO_ERROR(H5E_OHDR, H5E_NOTFOUND, FAIL, "'unknown' message type not found")
+
+done:
+    if(oh && H5AC_unprotect(oloc->file, H5AC_ind_dxpl_id, H5AC_OHDR, oloc->addr, oh, H5AC__NO_FLAGS_SET) < 0)
+	HDONE_ERROR(H5E_OHDR, H5E_PROTECT, FAIL, "unable to release object header")
+
+    FUNC_LEAVE_NOAPI(ret_value)
+}   /* H5O_check_msg_marked_test() */
+
diff --git a/src/H5Ounknown.c b/src/H5Ounknown.c
new file mode 100644
index 0000000..cd805a9
--- /dev/null
+++ b/src/H5Ounknown.c
@@ -0,0 +1,89 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * Copyright by the Board of Trustees of the University of Illinois.         *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the files COPYING and Copyright.html.  COPYING can be found at the root   *
+ * of the source code distribution tree; Copyright.html can be found at the  *
+ * root level of an installed copy of the electronic HDF5 document set and   *
+ * is linked from the top-level documents page.  It can also be found at     *
+ * http://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
+ * access to either file, you may request a copy from help@hdfgroup.org.     *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*-------------------------------------------------------------------------
+ *
+ * Created:             H5Ounknown.c
+ *                      Apr 19 2007
+ *                      Quincey Koziol <koziol@hdfgroup.org>
+ *
+ * Purpose:             Handle unknown message classes in a minimal way.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#define H5O_PACKAGE		/*suppress error about including H5Opkg	  */
+
+#include "H5private.h"		/* Generic Functions			*/
+#include "H5Eprivate.h"		/* Error handling		  	*/
+#include "H5FLprivate.h"	/* Free lists                           */
+#include "H5Opkg.h"             /* Object headers			*/
+
+
+/* PRIVATE PROTOTYPES */
+static herr_t H5O_unknown_free(void *_mesg);
+
+/* This message derives from H5O message class */
+const H5O_msg_class_t H5O_MSG_UNKNOWN[1] = {{
+    H5O_UNKNOWN_ID,           	/*message id number             */
+    "unknown",                	/*message name for debugging    */
+    0,				/*native message size           */
+    FALSE,			/* messages are sharable?       */
+    NULL,			/*decode message                */
+    NULL,			/*encode message                */
+    NULL,			/*copy the native value         */
+    NULL,			/*size of symbol table entry    */
+    NULL,                   	/*default reset method          */
+    H5O_unknown_free,	        /* free method			*/
+    NULL,			/* file delete method		*/
+    NULL,			/* link method			*/
+    NULL, 			/*set share method		*/
+    NULL,		    	/*can share method		*/
+    NULL,			/* pre copy native value to file */
+    NULL,			/* copy native value to file    */
+    NULL,			/* post copy native value to file */
+    NULL,			/* get creation index		*/
+    NULL,			/* set creation index		*/
+    NULL			/*debug the message             */
+}};
+
+/* Declare a free list to manage the H5O_unknown_t struct */
+H5FL_DEFINE_STATIC(H5O_unknown_t);
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5O_unknown_free
+ *
+ * Purpose:	Free's the message
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Tuesday, May 1, 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5O_unknown_free(void *mesg)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_unknown_free)
+
+    HDassert(mesg);
+
+    H5FL_FREE(H5O_unknown_t, mesg);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_unknown_free() */
+
diff --git a/src/Makefile.am b/src/Makefile.am
index b658771..40974e8 100755
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -70,7 +70,7 @@ libhdf5_la_SOURCES= H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5Olinfo.c H5Olink.c H5Omessage.c H5Omtime.c \
         H5Oname.c H5Onull.c H5Opline.c H5Orefcount.c \
         H5Osdspace.c H5Oshared.c H5Ostab.c \
-        H5Oshmesg.c H5Otest.c \
+        H5Oshmesg.c H5Otest.c H5Ounknown.c \
         H5P.c H5Pacpl.c H5Pdcpl.c H5Pdxpl.c H5Pfapl.c H5Pfcpl.c H5Pfmpl.c \
         H5Pgcpl.c \
         H5Plapl.c H5Plcpl.c H5Pocpl.c H5Pocpypl.c H5Pstrcpl.c H5Ptest.c \
diff --git a/src/Makefile.in b/src/Makefile.in
index a3c6817..6210d21 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -104,7 +104,7 @@ am_libhdf5_la_OBJECTS = H5.lo H5checksum.lo H5dbg.lo H5system.lo \
 	H5Odrvinfo.lo H5Odtype.lo H5Oefl.lo H5Ofill.lo H5Oginfo.lo \
 	H5Olayout.lo H5Olinfo.lo H5Olink.lo H5Omessage.lo H5Omtime.lo \
 	H5Oname.lo H5Onull.lo H5Opline.lo H5Orefcount.lo H5Osdspace.lo \
-	H5Oshared.lo H5Ostab.lo H5Oshmesg.lo H5Otest.lo H5P.lo \
+	H5Oshared.lo H5Ostab.lo H5Oshmesg.lo H5Otest.lo H5Ounknown.lo H5P.lo \
 	H5Pacpl.lo H5Pdcpl.lo H5Pdxpl.lo H5Pfapl.lo H5Pfcpl.lo \
 	H5Pfmpl.lo H5Pgcpl.lo H5Plapl.lo H5Plcpl.lo H5Pocpl.lo \
 	H5Pocpypl.lo H5Pstrcpl.lo H5Ptest.lo H5R.lo H5RC.lo H5RS.lo \
@@ -420,7 +420,7 @@ libhdf5_la_SOURCES = H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5Olinfo.c H5Olink.c H5Omessage.c H5Omtime.c \
         H5Oname.c H5Onull.c H5Opline.c H5Orefcount.c \
         H5Osdspace.c H5Oshared.c H5Ostab.c \
-        H5Oshmesg.c H5Otest.c \
+        H5Oshmesg.c H5Otest.c H5Ounknown.c \
         H5P.c H5Pacpl.c H5Pdcpl.c H5Pdxpl.c H5Pfapl.c H5Pfcpl.c H5Pfmpl.c \
         H5Pgcpl.c \
         H5Plapl.c H5Plcpl.c H5Pocpl.c H5Pocpypl.c H5Pstrcpl.c H5Ptest.c \
@@ -697,6 +697,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Oshmesg.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Ostab.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Otest.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Ounknown.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5P.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Pacpl.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/H5Pdcpl.Plo@am__quote@