[OpenMP] properly initialize buckets in __kmp_dephash_extend

[jschuchart]

Summary

The buckets are initialized in __kmp_dephash_create but when they are extended the memory is allocated but not NULL'd, potentially leaving some buckets uninitialized after all entries have been copied into the new allocation.

This commit makes sure the buckets are properly initialized with NULL before copying the entries.

[AndreyChurbanov]

LGTM

[protze.joachim]

LGTM as well.

@AndreyChurbanov please push the patch, Joseph doesn't have commit rights. Thx!

openmp/runtime/src/kmp_taskdeps.cpp

#else
   h = (kmp_dephash_t *)__kmp_thread_malloc(thread, size_to_allocate);
 #endif
 
   h->size = new_size;
   h->nelements = current_dephash->nelements;
   h->buckets = (kmp_dephash_entry **)(h + 1);
   h->generation = gen;
   h->nconflicts = 0;
+
+  // make sure buckets are properly initialized
+  for (size_t i = 0; i < new_size; i++) {
+    h->buckets[i] = NULL;
+  }
+
   // insert existing elements in the new table
   for (size_t i = 0; i < current_dephash->size; i++) {
     kmp_dephash_entry_t *next, *entry;
     for (entry = current_dephash->buckets[i]; entry; entry = next) {
       next = entry->next_in_bucket;
       // Compute the new hash using the new size, and insert the entry in
       // the new bucket.
       size_t new_bucket = __kmp_dephash_hash(entry->addr, h->size);