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.
(cherry picked from commit 1b2c2ca9a6a7d7e1fcd5c3302e203f2e2dabf0af)

1 files changed, 8 insertions, 7 deletions

diff --git a/src/H5Oalloc.c b/src/H5Oalloc.c
index c81bdf9..25052e7 100644
--- a/src/H5Oalloc.c
+++ b/src/H5Oalloc.c
@@ -2200,16 +2200,17 @@ 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 */