Fix HDFFV-10274. When deleting all (or almost all) of the messages in

an object header chunk, where the total amount deleted was greater than
64K, an error would occur due to an off by one error in the code that
handled that case.  Fixed this and added a test case.

1 files changed, 8 insertions, 7 deletions

diff --git a/src/H5Oalloc.c b/src/H5Oalloc.c
index 3512d3e..478d950 100644
--- a/src/H5Oalloc.c
+++ b/src/H5Oalloc.c
@@ -2434,16 +2434,17 @@ H5O_alloc_shrink_chunk(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned chunkno)
         oh->nmesgs++;
 
         /* Initialize new null message to make the chunk large enough */
-        oh->mesg[oh->nmesgs].type = H5O_MSG_NULL;
-        oh->mesg[oh->nmesgs].dirty = TRUE;
-        oh->mesg[oh->nmesgs].native = NULL;
-        oh->mesg[oh->nmesgs].raw = old_image + new_size + sizeof_msghdr - sizeof_chksum;
-        oh->mesg[oh->nmesgs].raw_size = MAX(H5O_ALIGN_OH(oh, min_chunk_size - total_msg_size),
+        curr_msg = &oh->mesg[oh->nmesgs - 1];
+        curr_msg->type = H5O_MSG_NULL;
+        curr_msg->dirty = TRUE;
+        curr_msg->native = NULL;
+        curr_msg->raw = old_image + new_size + sizeof_msghdr - sizeof_chksum;
+        curr_msg->raw_size = MAX(H5O_ALIGN_OH(oh, min_chunk_size - total_msg_size),
             sizeof_msghdr) - sizeof_msghdr;
-        oh->mesg[oh->nmesgs].chunkno = chunkno;
+        curr_msg->chunkno = chunkno;
 
         /* update the new chunk size */
-        new_size += oh->mesg[oh->nmesgs].raw_size + sizeof_msghdr;
+        new_size += curr_msg->raw_size + sizeof_msghdr;
     } /* end if */
 
     /* Check for changing the chunk #0 data size enough to need adjusting the flags */