Fix h5repack for variable-length datatyped datasets

release_docs/RELEASE.txt

@@ -599,6 +599,22 @@ Bug Fixes since HDF5-1.14.0 release
 
     Tools
     -----
+    - Fixed an issue in h5repack for variable-length typed datasets
+
+      When repacking datasets into a new file, h5repack tries to determines whether
+      it can use H5Ocopy to copy each dataset into the new file, or if it needs to
+      manually re-create the dataset, then read data from the old dataset and write
+      it to the new dataset. H5repack was previously using H5Ocopy for datasets with
+      variable-length datatypes, but this can be problematic if the global heap
+      addresses involved do not match exactly between the old and new files. These
+      addresses could change for a variety of reasons, such as the command-line options
+      provided to h5repack, how h5repack allocate space in the repacked file, etc.      
+      Since H5Ocopy does not currently perform any translation when these addresses
+      change, datasets that were repacked with H5Ocopy could become unreadable in the
+      new file. H5repack has been fixed to repack variable-length typed datasets without
+      using H5Ocopy to ensure that the new datasets always have the correct global heap
+      addresses.
+
     - Names of objects with square brackets will have trouble without the
       special argument, --no-compact-subset, on the h5dump command line.
 

tools/src/h5repack/h5repack_copy.c

@@ -653,6 +653,7 @@ do_copy_objects(hid_t fidin, hid_t fidout, trav_table_t *travt, pack_opt_t *opti
     int                ifil;
     int                is_ref = 0;
     htri_t             is_named;
+    htri_t             is_vlen = 0;
     hbool_t            limit_maxdims;
     hsize_t            size_dset;
     int                ret_value = 0;
@@ -806,6 +807,10 @@ do_copy_objects(hid_t fidin, hid_t fidout, trav_table_t *travt, pack_opt_t *opti
                     if (H5T_REFERENCE == H5Tget_class(ftype_id))
                         is_ref = 1;
 
+                    /* early detection of variable-length types */
+                    if ((is_vlen = H5Tdetect_class(ftype_id, H5T_VLEN)) < 0)
+                        H5TOOLS_GOTO_ERROR((-1), "H5Tdetect_class failed");
+
                     /* Check if the datatype is committed */
                     if ((is_named = H5Tcommitted(ftype_id)) < 0)
                         H5TOOLS_GOTO_ERROR((-1), "H5Tcommitted failed");
@@ -823,10 +828,16 @@ do_copy_objects(hid_t fidin, hid_t fidout, trav_table_t *travt, pack_opt_t *opti
                      * check if we should use H5Ocopy or not
                      * if there is a request for filters/layout, we read/write the object
                      * otherwise we do a copy using H5Ocopy
+                     *
+                     * Note that H5Ocopy is currently unsafe to use for objects that reside in
+                     * or interact with global heaps, such as variable-length datatypes. This
+                     * appears to be due to H5Ocopy not correctly translating in the case where
+                     * these objects move to different global heap addresses in the repacked
+                     * file.
                      *-------------------------------------------------------------------------
                      */
                     use_h5ocopy = !(options->op_tbl->nelems || options->all_filter == 1 ||
-                                    options->all_layout == 1 || is_ref || is_named);
+                                    options->all_layout == 1 || is_ref || is_vlen || is_named);
 
                     /*
                      * Check if we are using different source and destination VOL connectors.