Index: sparseset.c
===================================================================
--- sparseset.c (revision 190474)
+++ sparseset.c (working copy)
@@ -30,12 +30,14 @@
   unsigned int n_bytes = sizeof (struct sparseset_def)
                         + ((n_elms - 1) * 2 * sizeof (SPARSESET_ELT_TYPE));

-  /* We use xcalloc rather than xmalloc to silence some valgrind uninitialized
+  sparseset set = XNEWVAR(struct sparseset_def, n_bytes);
+
+  /* Mark the sparseset as defined to silence some valgrind uninitialized
      read errors when accessing set->sparse[n] when "n" is not, and never has
      been, in the set.  These uninitialized reads are expected, by design and
-     harmless.  If this turns into a performance problem due to some future
-     additional users of sparseset, we can revisit this decision.  */
-  sparseset set = (sparseset) xcalloc (1, n_bytes);
+     harmless.  */
+  VALGRIND_DISCARD (VALGRIND_MAKE_MEM_DEFINED (set, n_bytes));
+
   set->dense = &(set->elms[0]);
   set->sparse = &(set->elms[n_elms]);
   set->size = n_elms;