Merging in latest from upstream (HDFFV/hdf5:refs/heads/hdf5_1_10)

* commit 'a043211d9edf2df3ea8049bda4be6bdcbf0970e9':
  Delay checking if decoded message's "shareable" flag is appropriate for the message type until we've verified we understand the message type. Reduce size of H5O_msg_class_g to *not* include space for H5O_BOGUS_INVALID.  Make bogus messages shareable.  Add new bogus message test with shareable messages to cover the formerly problematic code.  Re-run gen_bogus.c to add this test case and also to fix the bogus_invalid messages that were no longer H5O_BOGUS_INVLAID due to a new message class being added in a previous commit.  Added comment to remind developers to run gen_bogus.c when adding a new message class.
  Remove H5O_BOGUS_INVALID_ID from H5O_msg_class_g initialization, since space for it was removed.
  Fortran wrappers for dataset obj header minimization API calls.

16 files changed, 305 insertions, 30 deletions

diff --git a/fortran/src/H5Fff.F90 b/fortran/src/H5Fff.F90
index 358e421..bf797b2 100644
--- a/fortran/src/H5Fff.F90
+++ b/fortran/src/H5Fff.F90
@@ -874,4 +874,97 @@ CONTAINS
 
   END SUBROUTINE h5fget_file_image_f
 
+!****s* H5F (F03)/h5fget_dset_no_attrs_hint_f_F03
+!
+! NAME
+!  h5fget_dset_no_attrs_hint_f
+!
+! PURPOSE
+!  Gets the value of the "minimize dataset headers" value which creates
+!  smaller dataset object headers when its set and no attributes are present.
+!
+! INPUTS
+!  file_id    - Target file identifier.
+!
+! OUTPUTS
+!  minimize   - Value of the setting.
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  January 2019
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5fget_dset_no_attrs_hint_f(file_id, minimize, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: file_id
+    LOGICAL        , INTENT(OUT)             :: minimize
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_minimize
+
+    INTERFACE
+       INTEGER FUNCTION h5fget_dset_no_attrs_hint_c(file_id, minimize) BIND(C, NAME='H5Fget_dset_no_attrs_hint')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: file_id
+         LOGICAL(C_BOOL), INTENT(OUT) :: minimize
+       END FUNCTION h5fget_dset_no_attrs_hint_c
+    END INTERFACE
+
+    hdferr = INT(h5fget_dset_no_attrs_hint_c(file_id, c_minimize))
+
+    ! Transfer value of C C_BOOL type to Fortran LOGICAL 
+    minimize = c_minimize
+
+  END SUBROUTINE h5fget_dset_no_attrs_hint_f
+
+!****s* H5F (F03)/h5fset_dset_no_attrs_hint_f_F03
+!
+! NAME
+!  h5fset_dset_no_attrs_hint_f
+!
+! PURPOSE
+!  Sets the value of the "minimize dataset headers" value which creates
+!  smaller dataset object headers when its set and no attributes are present.
+!
+! INPUTS
+!  file_id    - Target file identifier.
+!  minimize   - Value of the setting.
+!
+! OUTPUTS
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  January 2019
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5fset_dset_no_attrs_hint_f(file_id, minimize, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: file_id
+    LOGICAL        , INTENT(IN)              :: minimize
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_minimize
+
+    INTERFACE
+       INTEGER FUNCTION h5fset_dset_no_attrs_hint_c(file_id, minimize) BIND(C, NAME='H5Fset_dset_no_attrs_hint')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: file_id
+         LOGICAL(C_BOOL), INTENT(IN), VALUE :: minimize
+       END FUNCTION h5fset_dset_no_attrs_hint_c
+    END INTERFACE
+
+    ! Transfer value of Fortran LOGICAL to C C_BOOL type
+    c_minimize = minimize
+
+    hdferr = INT(h5fset_dset_no_attrs_hint_c(file_id, c_minimize))
+
+  END SUBROUTINE h5fset_dset_no_attrs_hint_f
+
 END MODULE H5F
+
diff --git a/fortran/src/H5Pff.F90 b/fortran/src/H5Pff.F90
index 455c72e..13a2953 100644
--- a/fortran/src/H5Pff.F90
+++ b/fortran/src/H5Pff.F90
@@ -8023,8 +8023,97 @@ SUBROUTINE h5pget_virtual_dsetname_f(dcpl_id, index, name, hdferr, name_len)
 
 END SUBROUTINE h5pget_virtual_dsetname_f
 
+!****s* H5P (F03)/h5pget_dset_no_attrs_hint_f_F03
+!
+! NAME
+!  h5pget_dset_no_attrs_hint_f
+!
+! PURPOSE
+!  Gets the value of the "minimize dataset headers" value which creates
+!  smaller dataset object headers when its set and no attributes are present.
+!
+! INPUTS
+!  dcpl_id    - Target dataset creation property list identifier.
+!
+! OUTPUTS
+!  minimize   - Value of the setting.
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  January 2019
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5pget_dset_no_attrs_hint_f(dcpl_id, minimize, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: dcpl_id
+    LOGICAL        , INTENT(OUT)             :: minimize
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_minimize
 
-END MODULE H5P
+    INTERFACE
+       INTEGER FUNCTION h5pget_dset_no_attrs_hint_c(dcpl_id, minimize) BIND(C, NAME='H5Pget_dset_no_attrs_hint')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: dcpl_id
+         LOGICAL(C_BOOL), INTENT(OUT) :: minimize
+       END FUNCTION h5pget_dset_no_attrs_hint_c
+    END INTERFACE
+
+    hdferr = INT(h5pget_dset_no_attrs_hint_c(dcpl_id, c_minimize))
 
+    ! Transfer value of C C_BOOL type to Fortran LOGICAL 
+    minimize = c_minimize
 
+   END SUBROUTINE h5pget_dset_no_attrs_hint_f
+
+!****s* H5P (F03)/h5pset_dset_no_attrs_hint_f_F03
+!
+! NAME
+!  h5pset_dset_no_attrs_hint_f
+!
+! PURPOSE
+!  Sets the value of the "minimize dataset headers" value which creates
+!  smaller dataset object headers when its set and no attributes are present.
+!
+! INPUTS
+!  dcpl_id    - Target dataset creation property list identifier.
+!  minimize   - Value of the setting.
+!
+! OUTPUTS
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  January 2019
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5pset_dset_no_attrs_hint_f(dcpl_id, minimize, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: dcpl_id
+    LOGICAL        , INTENT(IN)              :: minimize
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_minimize
+
+    INTERFACE
+       INTEGER FUNCTION h5pset_dset_no_attrs_hint_c(dcpl_id, minimize) BIND(C, NAME='H5Pset_dset_no_attrs_hint')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: dcpl_id
+         LOGICAL(C_BOOL), INTENT(IN), VALUE :: minimize
+       END FUNCTION h5pset_dset_no_attrs_hint_c
+    END INTERFACE
+
+    ! Transfer value of Fortran LOGICAL to C C_BOOL type
+    c_minimize = minimize
+
+    hdferr = INT(h5pset_dset_no_attrs_hint_c(dcpl_id, c_minimize))
+
+  END SUBROUTINE h5pset_dset_no_attrs_hint_f
+
+END MODULE H5P
 
diff --git a/fortran/src/hdf5_fortrandll.def.in b/fortran/src/hdf5_fortrandll.def.in
index 3a5a91f..f36a5c8 100644
--- a/fortran/src/hdf5_fortrandll.def.in
+++ b/fortran/src/hdf5_fortrandll.def.in
@@ -98,6 +98,8 @@ H5F_mp_H5FIS_HDF5_F
 H5F_mp_H5FGET_NAME_F
 H5F_mp_H5FGET_FILESIZE_F
 H5F_mp_H5FGET_FILE_IMAGE_F
+H5F_mp_H5FGET_DSET_NO_ATTRS_HINT_F
+H5F_mp_H5FSET_DSET_NO_ATTRS_HINT_F
 ; H5G
 H5G_mp_H5GOPEN_F
 H5G_mp_H5GCREATE_F
@@ -328,6 +330,8 @@ H5P_mp_H5PGET_VIRTUAL_VSPACE_F
 H5P_mp_H5PGET_VIRTUAL_SRCSPACE_F
 H5P_mp_H5PGET_VIRTUAL_FILENAME_F
 H5P_mp_H5PGET_VIRTUAL_DSETNAME_F
+H5P_mp_H5PGET_DSET_NO_ATTRS_HINT_F
+H5P_mp_H5PSET_DSET_NO_ATTRS_HINT_F
 ; Parallel
 @H5_NOPAREXP@H5P_mp_H5PSET_FAPL_MPIO_F
 @H5_NOPAREXP@H5P_mp_H5PGET_FAPL_MPIO_F
diff --git a/fortran/test/tH5F.F90 b/fortran/test/tH5F.F90
index ee386dd..75a7748 100644
--- a/fortran/test/tH5F.F90
+++ b/fortran/test/tH5F.F90
@@ -841,5 +841,4 @@ CONTAINS
 
         END SUBROUTINE file_space
 
-
 END MODULE TH5F
diff --git a/fortran/test/tH5P.F90 b/fortran/test/tH5P.F90
index 563926b..ed35b63 100644
--- a/fortran/test/tH5P.F90
+++ b/fortran/test/tH5P.F90
@@ -444,6 +444,7 @@ SUBROUTINE test_chunk_cache(cleanup, total_error)
   INTEGER(size_t) rdcc_nelmts
   INTEGER(size_t) rdcc_nbytes
   REAL :: rdcc_w0
+  LOGICAL :: minimize              ! Flag for minimized headers
 
   CALL h5_fixname_f(filename, fix_filename, H5P_DEFAULT_F, error)
   IF (error .NE. 0) THEN
@@ -648,6 +649,57 @@ SUBROUTINE test_chunk_cache(cleanup, total_error)
   CALL verify("H5Pget_chunk_cache_f", INT(nbytes_2), INT(nbytes_4), total_error)
   CALL verify("H5Pget_chunk_cache_f", w0_3, w0_4, total_error)
 
+  ! Check that the dataset object header minimization hint
+  ! can be set and retrieved.
+
+  ! H5P version
+  ! Check the default value
+  minimize = .TRUE.
+  CALL h5pget_dset_no_attrs_hint_f(dcpl, minimize, error)
+  CALL check("h5pget_dset_no_attrs_hint_f",error,total_error)
+  if(error .eq. 0 .and. minimize .neqv. .FALSE.) then
+    total_error = total_error + 1
+    write(*,*) "Default dataset minimize flag was incorrect (H5P)"
+  endif
+
+  ! Check setter
+  minimize = .TRUE.
+  CALL h5pset_dset_no_attrs_hint_f(dcpl, minimize, error)
+  CALL check("h5pset_dset_no_attrs_hint_f",error,total_error)
+
+  ! Check getter
+  minimize = .FALSE.
+  CALL h5pget_dset_no_attrs_hint_f(dcpl, minimize, error)
+  CALL check("h5pget_dset_no_attrs_hint_f",error,total_error)
+  if(error .eq. 0 .and. minimize .neqv. .TRUE.) then
+    total_error = total_error + 1
+    write(*,*) "Unable to get correct dataset minimize flag (H5P)"
+  endif
+
+  ! H5F version
+  ! Check the default value
+  minimize = .TRUE.
+  CALL h5fget_dset_no_attrs_hint_f(fid, minimize, error)
+  CALL check("h5fget_dset_no_attrs_hint_f",error,total_error)
+  if(error .eq. 0 .and. minimize .neqv. .FALSE.) then
+    total_error = total_error + 1
+    write(*,*) "Default dataset minimize flag was incorrect (H5F)"
+  endif
+
+  ! Check setter
+  minimize = .TRUE.
+  CALL h5fset_dset_no_attrs_hint_f(fid, minimize, error)
+  CALL check("h5fset_dset_no_attrs_hint_f",error,total_error)
+
+  ! Check getter
+  minimize = .FALSE.
+  CALL h5fget_dset_no_attrs_hint_f(fid, minimize, error)
+  CALL check("h5fget_dset_no_attrs_hint_f",error,total_error)
+  if(error .eq. 0 .and. minimize .neqv. .TRUE.) then
+    total_error = total_error + 1
+    write(*,*) "Unable to get correct dataset minimize flag (H5F)"
+  endif
+
 ! Close
 
   CALL H5Dclose_f(dsid, error)
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 62ad9ad..d33b7eb 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -197,7 +197,17 @@ New Features
 
     Fortran Library:
     ----------------
-    -
+    - Added wrappers for dataset object header minimization calls.
+      (see the note for TRILAB-45, above)
+
+      New API calls:
+
+      h5fget_dset_no_attrs_hint_f
+      h5fset_dset_no_attrs_hint_f
+      h5pget_dset_no_attrs_hint_f
+      h5pset_dset_no_attrs_hint_f
+
+      (DER - 2019/01/09, TRILAB-45)
 
     C++ Library:
     ------------
@@ -370,7 +380,7 @@ Bug Fixes since HDF5-1.10.3 release
 
     - Made Fortran specific subroutines PRIVATE in generic procedures.
 
-      Effected generic procedures were functions in H5A, H5D, H5P, H5R and H5T.
+      Affected generic procedures were functions in H5A, H5D, H5P, H5R and H5T.
 
       (MSB, 2018/12/04, HDFFV-10511)
 
diff --git a/src/H5Fpublic.h b/src/H5Fpublic.h
index 6274eb0..8a475d1 100644
--- a/src/H5Fpublic.h
+++ b/src/H5Fpublic.h
@@ -233,7 +233,7 @@ H5_DLL herr_t H5Fflush(hid_t object_id, H5F_scope_t scope);
 H5_DLL herr_t H5Fclose(hid_t file_id);
 H5_DLL hid_t  H5Fget_create_plist(hid_t file_id);
 H5_DLL hid_t  H5Fget_access_plist(hid_t file_id);
-H5_DLL herr_t H5Fget_intent(hid_t file_id, unsigned * intent);
+H5_DLL herr_t H5Fget_intent(hid_t file_id, unsigned *intent);
 H5_DLL ssize_t H5Fget_obj_count(hid_t file_id, unsigned types);
 H5_DLL ssize_t H5Fget_obj_ids(hid_t file_id, unsigned types, size_t max_objs, hid_t *obj_id_list);
 H5_DLL herr_t H5Fget_vfd_handle(hid_t file_id, hid_t fapl, void **file_handle);
diff --git a/src/H5Obogus.c b/src/H5Obogus.c
index 92fd218..f10268e 100644
--- a/src/H5Obogus.c
+++ b/src/H5Obogus.c
@@ -49,7 +49,7 @@ const H5O_msg_class_t H5O_MSG_BOGUS_VALID[1] = {{
     H5O_BOGUS_VALID_ID,		/*message id number             */
     "bogus valid",             	/*message name for debugging    */
     0,     	                /*native message size           */
-    0,				/* messages are sharable?       */
+    H5O_SHARE_IS_SHARABLE,      /* messages are sharable?       */
     H5O__bogus_decode,        	/*decode message                */
     H5O_bogus_encode,        	/*encode message                */
     NULL,          	        /*copy the native value         */
@@ -73,7 +73,7 @@ const H5O_msg_class_t H5O_MSG_BOGUS_INVALID[1] = {{
     H5O_BOGUS_INVALID_ID, 	/*message id number             */
     "bogus invalid",          	/*message name for debugging    */
     0,                          /*native message size           */
-    0,                          /* messages are sharable?       */
+    H5O_SHARE_IS_SHARABLE,      /* messages are sharable?       */
     H5O__bogus_decode,          /*decode message                */
     H5O__bogus_encode,          /*encode message                */
     NULL,                       /*copy the native value         */
diff --git a/src/H5Ocache.c b/src/H5Ocache.c
index 59e1705..1d69028 100644
--- a/src/H5Ocache.c
+++ b/src/H5Ocache.c
@@ -1402,10 +1402,9 @@ H5O__chunk_deserialize(H5O_t *oh, haddr_t addr, size_t len, const uint8_t *image
             HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "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, FAIL, "bad flag combination for message")
-        if((flags & H5O_MSG_FLAG_SHAREABLE)
-                && H5O_msg_class_g[id]
-                && !(H5O_msg_class_g[id]->share_flags & H5O_SHARE_IS_SHARABLE))
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "message of unsharable class flagged as sharable")
+        /* Delay checking the "shareable" flag until we've made sure id
+         * references a valid message class that this version of the library
+         * knows about */
 
         /* Reserved bytes/creation index */
         if(oh->version == H5O_VERSION_1)
@@ -1517,9 +1516,17 @@ H5O__chunk_deserialize(H5O_t *oh, haddr_t addr, size_t len, const uint8_t *image
                     mesgs_modified = TRUE;
                 } /* end if */
             } /* end if */
-            else
+            else {
+                /* Check for message of unshareable class marked as "shareable"
+                 */
+                if((flags & H5O_MSG_FLAG_SHAREABLE)
+                        && H5O_msg_class_g[id]
+                        && !(H5O_msg_class_g[id]->share_flags & H5O_SHARE_IS_SHARABLE))
+                    HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "message of unshareable class flagged as shareable")
+
                 /* Set message class for "known" messages */
                 mesg->type = H5O_msg_class_g[id];
+            } /* end else */
 
             /* Do some inspection/interpretation of new messages from this chunk */
             /* (detect continuation messages, ref. count messages, etc.) */
diff --git a/src/H5Oint.c b/src/H5Oint.c
index 38d73c0..09e6bb8 100644
--- a/src/H5Oint.c
+++ b/src/H5Oint.c
@@ -126,12 +126,7 @@ const H5O_msg_class_t *const H5O_msg_class_g[] = {
     H5O_MSG_REFCOUNT,		/*0x0016 Object's ref. count		*/
     H5O_MSG_FSINFO,		/*0x0017 Free-space manager info        */
     H5O_MSG_MDCI,               /*0x0018 Metadata cache image           */
-    H5O_MSG_UNKNOWN,		/*0x0019 Placeholder for unknown message */
-#ifdef H5O_ENABLE_BOGUS
-    H5O_MSG_BOGUS_INVALID, 	/*0x001A "Bogus invalid" (for testing) 	*/
-#else /* H5O_ENABLE_BOGUS */
-    NULL,                       /*0x001A "Bogus invalid" (for testing) 	*/
-#endif /* H5O_ENABLE_BOGUS */
+    H5O_MSG_UNKNOWN		/*0x0019 Placeholder for unknown message */
 };
 
 /* Format version bounds for object header */
diff --git a/src/H5Omessage.c b/src/H5Omessage.c
index e156dcd..b38d74e 100644
--- a/src/H5Omessage.c
+++ b/src/H5Omessage.c
@@ -1598,16 +1598,23 @@ H5O_msg_is_shared(unsigned type_id, const void *mesg)
     FUNC_ENTER_NOAPI_NOINIT_NOERR
 
     /* Check args */
-    HDassert(type_id < NELMTS(H5O_msg_class_g));
-    type = H5O_msg_class_g[type_id];    /* map the type ID to the actual type object */
-    HDassert(type);
-    HDassert(mesg);
-
-    /* If messages in a class aren't sharable, then obviously this message isn't shared! :-) */
-    if(type->share_flags & H5O_SHARE_IS_SHARABLE)
-        ret_value = H5O_IS_STORED_SHARED(((const H5O_shared_t *)mesg)->type);
-    else
+#ifdef H5O_ENABLE_BOGUS
+    if(type_id >= NELMTS(H5O_msg_class_g))
         ret_value = FALSE;
+    else
+#endif /* H5O_ENABLE_BOGUS */
+    {
+        HDassert(type_id < NELMTS(H5O_msg_class_g));
+        type = H5O_msg_class_g[type_id];    /* map the type ID to the actual type object */
+        HDassert(type);
+        HDassert(mesg);
+
+        /* If messages in a class aren't sharable, then obviously this message isn't shared! :-) */
+        if(type->share_flags & H5O_SHARE_IS_SHARABLE)
+            ret_value = H5O_IS_STORED_SHARED(((const H5O_shared_t *)mesg)->type);
+        else
+            ret_value = FALSE;
+    } /* end block/else */
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_is_shared() */
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index 19d90c5..a3cc27f 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -29,7 +29,7 @@
 #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   27              /* # of types of messages            */
+#define H5O_MSG_TYPES   26              /* # of types of messages            */
 #define H5O_MAX_CRT_ORDER_IDX 65535     /* Max. creation order index value   */
 
 /* Versions of object header structure */
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index 7868123..34683fe 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -226,11 +226,11 @@ typedef struct H5O_copy_t {
  * Note: Must increment H5O_MSG_TYPES in H5Opkg.h and update H5O_msg_class_g
  *      in H5O.c when creating a new message type.  Also bump the value of
  *      H5O_BOGUS_INVALID_ID, below, to be one greater than the value of
- *      H5O_UNKNOWN_ID.
+ *      H5O_UNKNOWN_ID, and re-run gen_bogus.c.
  *
  * (this should never exist in a file)
  */
-#define H5O_BOGUS_INVALID_ID	0x001A  /* "Bogus invalid" Message.  */
+#define H5O_BOGUS_INVALID_ID	0x001a  /* "Bogus invalid" Message.  */
 
 /* Shared object message types.
  * Shared objects can be committed, in which case the shared message contains
@@ -650,6 +650,7 @@ typedef struct H5O_layout_t {
  */
 #define H5O_BOGUS_VALUE         0xdeadbeef
 typedef struct H5O_bogus_t {
+    H5O_shared_t        sh_loc;         /* Shared message info (must be first) */
     unsigned u;                         /* Hold the bogus info */
 } H5O_bogus_t;
 #endif /* H5O_ENABLE_BOGUS */
diff --git a/test/gen_bogus.c b/test/gen_bogus.c
index ec29eb9..237b024 100644
--- a/test/gen_bogus.c
+++ b/test/gen_bogus.c
@@ -89,6 +89,14 @@ generate_datasets(hid_t loc_id, unsigned bogus_id)
     if((did = H5Dcreate2(loc_id, "Dataset4", H5T_NATIVE_INT, sid, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0) goto error;
     if(H5Dclose(did) < 0) goto error;
 
+    /* Set "shareable" message flag for bogus message */
+    bogus_flags = H5O_MSG_FLAG_SHAREABLE;
+    if(H5Pset(dcpl, H5O_BOGUS_MSG_FLAGS_NAME, &bogus_flags) < 0) goto error;
+
+    /* Create fourth dataset, with "shareable" message flag */
+    if((did = H5Dcreate2(loc_id, "Dataset5", H5T_NATIVE_INT, sid, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0) goto error;
+    if(H5Dclose(did) < 0) goto error;
+
     /* Close dataset creation property list */
     if(H5Pclose(dcpl) < 0) goto error;
 
diff --git a/test/ohdr.c b/test/ohdr.c
index fada430..3f61660 100644
--- a/test/ohdr.c
+++ b/test/ohdr.c
@@ -1399,6 +1399,16 @@ test_unknown(unsigned bogus_id, char *filename, hid_t fapl)
 
     PASSED();
 
+    TESTING("object with unknown header message & 'shareable' flag set");
+
+    /* Open the dataset with the unknown header message, adn "shareable" flag */
+    if((did = H5Dopen2(loc_bogus, "Dataset5", H5P_DEFAULT)) < 0)
+        FAIL_STACK_ERROR
+    if(H5Dclose(did) < 0)
+        FAIL_STACK_ERROR
+
+    PASSED();
+
     TESTING("object in r/o file with unknown header message & 'fail if unknown and open for write' flag set");
 
     /* Open the dataset with the unknown header message, and "fail if unknown and open for write" flag */
diff --git a/test/tbogus.h5 b/test/tbogus.h5
index 91ab76f..efcbd79 100644
--- a/test/tbogus.h5
+++ b/test/tbogus.h5