2.21.1  Data-Sharing Attribute Rules
   2.21.1.1  Variables Referenced in a Construct
   2.21.1.2  Variables Referenced in a Region but not in a Construct
  2.21.2  threadprivate Directive
  2.21.3  List Item Privatization
  2.21.4  Data-Sharing Attribute Clauses
   2.21.4.1  default Clause
   2.21.4.2  shared Clause
   2.21.4.3  private Clause
   2.21.4.4  firstprivate Clause
   2.21.4.5  lastprivate Clause
   2.21.4.6  linear Clause
  2.21.5  Reduction Clauses and Directives
   2.21.5.1  Properties Common to All Reduction Clauses
   2.21.5.2  Reduction Scoping Clauses
   2.21.5.3  Reduction Participating Clauses
   2.21.5.4  reduction Clause
   2.21.5.5  task_reduction Clause
   2.21.5.6  in_reduction Clause
   2.21.5.7  declare reduction Directive
  2.21.6  Data Copying Clauses
   2.21.6.1  copyin Clause
   2.21.6.2  copyprivate Clause
  2.21.7  Data-Mapping Attribute Rules, Clauses, and Directives
   2.21.7.1  map Clause
   2.21.7.2  Pointer Initialization for Device Data Environments
   2.21.7.3  defaultmap Clause
   2.21.7.4  declare mapper Directive