Fix uninitialized variable in dshash.c.

A bugfix for commit 8c0d7bafad36434cb08ac2c78e69ae72c194ca20.  The code
would have crashed if hashtable->size_log2 ever had the same value as
hashtable->control->size_log2 by coincidence.

Per Valgrind.

Author: Thomas Munro
Reported-By: Tomas Vondra
Discussion: https://postgr.es/m/e72fb33c-4f31-f276-e972-263d9b59554d%402ndquadrant.com

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 448e0587253e01f2c830e389d105f025908bbd74..dd875730670de1190030305a0ad8404571f7e9b0 100644 (file)
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -249,6 +249,7 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
    }
    hash_table->buckets = dsa_get_address(area,
                                          hash_table->control->buckets);
+   hash_table->size_log2 = hash_table->control->size_log2;
 
    return hash_table;
 }
@@ -280,6 +281,14 @@ dshash_attach(dsa_area *area, const dshash_parameters *params,
    hash_table->find_exclusively_locked = false;
    Assert(hash_table->control->magic == DSHASH_MAGIC);
 
+   /*
+    * These will later be set to the correct values by
+    * ensure_valid_bucket_pointers(), at which time we'll be holding a
+    * partition lock for interlocking against concurrent resizing.
+    */
+   hash_table->buckets = NULL;
+   hash_table->size_log2 = 0;
+
    return hash_table;
 }