Fix the segmentation fault that occurs when running test/vfd_swmr_group_writer with one million old style groups.

(A) src/vfd_swmr_enlarge_shadow_index():
--When enlarging the metadata file index entries, HDmalloc() is used to allocate space for the index entries,
but they are later freed at file close via H5MM_xfree() in H5F__dest().
This is corrected to use H5MM_calloc() instead to be consistent.  Note that entries are initially allocated
also via H5MM_calloc() in H5F__vfd_swmr_create_index().
--If the pointer to the old metadata file index entries exists (shared->old_mdf_idx), need to free
the old entries via H5MM_xfree().
(B) test/testvfdswmr.sh.in:
--The test is added to verify that the bug is resolved.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/H5Fvfd_swmr.c b/src/H5Fvfd_swmr.c
index 13170af..ebb57d6 100644
--- a/src/H5Fvfd_swmr.c
+++ b/src/H5Fvfd_swmr.c
@@ -1756,7 +1756,7 @@ vfd_swmr_enlarge_shadow_index(H5F_t *f)
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "shadow-file allocation failed for index")
     }
 
-    new_mdf_idx = HDmalloc(new_mdf_idx_len * sizeof(new_mdf_idx[0]));
+    new_mdf_idx = H5MM_calloc(new_mdf_idx_len * sizeof(new_mdf_idx[0]));
 
     if (new_mdf_idx == NULL) {
         (void)H5MV_free(f, idx_addr, idx_size);
@@ -1774,6 +1774,12 @@ vfd_swmr_enlarge_shadow_index(H5F_t *f)
     ret_value = shared->mdf_idx = new_mdf_idx;
     shared->mdf_idx_len         = new_mdf_idx_len;
 
+    if(shared->old_mdf_idx)
+         H5MM_xfree(f->shared->old_mdf_idx);
+
+    shared->old_mdf_idx         = old_mdf_idx;
+    f->shared->old_mdf_idx_len  = old_mdf_idx_len;
+
     /* Postpone reclamation of the old index until max_lag ticks from now.
      * It's only necessary to wait until after the new index is in place,
      * so it's possible that some disused shadow storage will build up