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)

2 files changed, 106 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 */
diff --git a/test/tattr.c b/test/tattr.c
index 283874a..73962c5 100644
--- a/test/tattr.c
+++ b/test/tattr.c
@@ -10552,6 +10552,102 @@ test_attr_bug8(hid_t fcpl, hid_t fapl)
 
 /****************************************************************
 **
+**  test_attr_bug9(): Test basic H5A (attribute) code.
+**      (Really tests object header code).
+**      Tests adding several large attributes to an object until
+**      they convert to dense storage.  The total size of all
+**      attributes is larger than 64K, causing the internal
+**      object header code to, after merging the deleted
+**      messages in to a NULL message, shrink the object header
+**      chunk.  Do this twice: once with only attributes in the
+**      object header chunk and once with a (small) soft link in
+**      the chunk as well.  In both cases, the shrunk chunk will
+**      initally be too small and a new NULL message must be
+**      created.
+**
+****************************************************************/
+static void
+test_attr_bug9(hid_t fcpl, hid_t fapl)
+{
+    hid_t   fid;            /* File ID */
+    hid_t   gid;            /* Group ID */
+    hid_t   aid;            /* Attribute ID */
+    hid_t   sid;            /* Dataspace ID */
+    hsize_t dims[1] = {32768}; /* Attribute dimensions */
+    int create_link;        /* Whether to create a soft link */
+    unsigned max_compact;   /* Setting from fcpl */
+    unsigned min_dense;     /* Setting from fcpl */
+    char aname[11];         /* Attribute name */
+    unsigned i;             /* Local index variable */
+    herr_t  ret;            /* Generic return status */
+
+    /* Output message about test being performed */
+    MESSAGE(5, ("Testing that attributes can always be added to named datatypes\n"));
+
+    /* Create dataspace */
+    sid = H5Screate_simple(1, dims, NULL);
+    CHECK(sid, FAIL, "H5Screate_simple");
+
+    /* Obtain attribute phase change settings */
+    ret = H5Pget_attr_phase_change(fcpl, &max_compact, &min_dense);
+    CHECK(ret, FAIL, "H5Pget_attr_phase_change");
+
+    /* Run with and without the soft link */
+    for(create_link = 0; create_link < 2; create_link++) {
+        /* Create file */
+        fid = H5Fcreate(FILENAME, H5F_ACC_TRUNC, fcpl, fapl);
+        CHECK(fid, FAIL, "H5Fcreate");
+
+        /* Create second group */
+        gid = H5Gcreate2(fid, "group", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+        CHECK(gid, FAIL, "H5Gcreate2");
+
+        /* Close second group */
+        ret = H5Gclose(gid);
+        CHECK(ret, FAIL, "H5Gclose");
+
+        /* Open root group */
+        gid = H5Gopen2(fid, "/", H5P_DEFAULT);
+        CHECK(gid, FAIL, "H5Gopen2");
+
+        /* Create enough attributes to cause a change to dense storage */
+        for(i = 0; i < max_compact + 1; i++) {
+            /* Create attribute */
+            snprintf(aname, sizeof(aname), "%u", i);
+            aid = H5Acreate2(gid, aname, H5T_NATIVE_CHAR, sid, H5P_DEFAULT, H5P_DEFAULT);
+            CHECK(aid, FAIL, "H5Acreate2");
+
+            /* Close attribute */
+            ret = H5Aclose(aid);
+            CHECK(ret, FAIL, "H5Aclose");
+
+            /* Create enough soft links that exactly one goes into chunk 1 if
+             * requested */
+            if(i == 0 && create_link) {
+                ret = H5Lcreate_soft("b", gid, "a", H5P_DEFAULT, H5P_DEFAULT);
+                CHECK(ret, FAIL, "H5Lcreate_soft");
+                ret = H5Lcreate_soft("d", gid, "c", H5P_DEFAULT, H5P_DEFAULT);
+                CHECK(ret, FAIL, "H5Lcreate_soft");
+                ret = H5Lcreate_soft("f", gid, "e", H5P_DEFAULT, H5P_DEFAULT);
+                CHECK(ret, FAIL, "H5Lcreate_soft");
+            } /* end if */
+        } /* end for */
+
+        /* Close IDs */
+        ret = H5Gclose(gid);
+        CHECK(ret, FAIL, "H5Gclose");
+
+        ret = H5Fclose(fid);
+        CHECK(ret, FAIL, "H5Fclose");
+    } /* end for */
+
+    /* Close dataspace */
+    ret = H5Sclose(sid);
+    CHECK(ret, FAIL, "H5Sclose");
+}   /* test_attr_bug9() */
+
+/****************************************************************
+**
 **  test_attr(): Main H5A (attribute) testing routine.
 **
 ****************************************************************/
@@ -10698,6 +10794,7 @@ test_attr(void)
                 test_attr_bug6(my_fcpl, my_fapl);               /* Test reading empty attribute */
                 test_attr_bug7(my_fcpl, my_fapl);               /* Test creating and deleting large attributes in ohdr chunk 0 */
                 test_attr_bug8(my_fcpl, my_fapl);               /* Test attribute expanding object header with undecoded messages */
+                test_attr_bug9(my_fcpl, my_fapl);               /* Test large attributes converting to dense storage */
             } /* end for */
         } /* end if */
         else {
@@ -10726,6 +10823,7 @@ test_attr(void)
              * header format and in fact fails if used with the old format, due
              * to the attributes being larger than 64K */
             test_attr_bug8(fcpl, my_fapl);                      /* Test attribute expanding object header with undecoded messages */
+            test_attr_bug9(fcpl, my_fapl);                      /* Test large attributes converting to dense storage */
         } /* end else */
     } /* end for */