TAO/TAO_IDL/ast/ast_recursive.cpp

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  63 */
  64
  65 // EXPLANATION: The CORBA spec says that the only legal use of recursive types is
  66 // in a manifest sequence declared inside a struct or union whose base type is
  67 // the struct or union.
  68
  69 // ALGORITHM FOR CHECK:
  70 // Sequences push a NULL on the scope stack to mark where in the scope nesting
  71 // they appear.
  72
  73 // - If the type is not a struct or union, return FALSE (legal use of type).
  74 // - Otherwise check up the scope stack, looking for this base type. If we
  75 //   find a NULL return FALSE (legal use of type, since it is inside some
  76 //   sequence). If we find the type on the stack, return TRUE (illegal use
  77 //   since it was not bracketed by a sequence). If we don't find the base
  78 //   type nor a sequence, return FALSE (legal use, since we're not nested).
  79
  80 #include "ast_union.h"
  81 #include "utl_stack.h"
  82 #include "global_extern.h"
  83 #include "nr_extern.h"
  84
  85 bool
  86 AST_illegal_interface_recursion (AST_Decl *t)
  87 {
  88   // Can't be 0 since we know we have an interface or valuetype.
  89   AST_Decl *d = 0;
  90
  91   // If we encounter the argument in an enclosing scope, it's illegal.
  92   for (UTL_ScopeStackActiveIterator i (idl_global->scopes ());
  93        !i.is_done ();
  94        i.next ())
  95     {
  96       d = ScopeAsDecl (i.item ());
  97
  98       // Exceptions cannot be recursive, but may contain a reference
  99       // to the interface they are defined in.
 100       if (d->node_type () == AST_Decl::NT_except)
 101         {
 102           return false;
 103         }
 104
 105       if (d == t)
 106         {
 107           return true;
 108         }
 109     }
 110
 111   return false;
 112 }
 113
 114 bool
 115 AST_illegal_recursive_type (AST_Decl *t)
 116 {
 117   if (t == 0)
 118     {
 119       return false;
 120     }
 121
 122   AST_Decl::NodeType nt;
 123   AST_Type *ut = dynamic_cast<AST_Type*> (t);
 124
 125   if (ut != 0)
 126     {
 127       ut = ut->unaliased_type ();
 128       nt = ut->node_type ();
 129     }
 130   else
 131     {
 132       nt = t->node_type ();
 133     }
 134
 135   if (nt == AST_Decl::NT_interface)
 136     {
 137       // Check for interface->struct/union->....->interface nesting.
 138 //      return AST_illegal_interface_recursion (t);
 139     }
 140   else if (nt != AST_Decl::NT_struct && nt != AST_Decl::NT_union)
 141     {
 142       // Structs and unions fall through to the check below.
 143       return false;  // NOT ILLEGAL.
 144     }
 145
 146   bool check_for_struct = false;
 147   bool check_for_union = false;
 148   AST_Structure  *st1 = 0;
 149   AST_Union  *un1 = 0;
 150
 151   // Narrow the type appropriately so comparison will work.
 152   if (t->node_type () == AST_Decl::NT_struct)
 153     {
 154       check_for_struct = true;
 155       st1 = dynamic_cast<AST_Structure*> (t);
 156
 157       if (st1 == 0)
 158         {
 159           return false;  // NOT ILLEGAL.
 160         }
 161     }
 162   else if (t->node_type () == AST_Decl::NT_union)
 163     {
 164       check_for_union = true;
 165       un1 = dynamic_cast<AST_Union*> (t);
 166
 167       if (un1 == 0)
 168         {
 169           return false;  // NOT ILLEGAL.
 170         }
 171     }
 172
 173   UTL_Scope  *s = 0;
 174   AST_Structure *st2 = 0;
 175   AST_Union *un2 = 0;
 176
 177   // OK, iterate up the stack.
 178   for (UTL_ScopeStackActiveIterator i (idl_global->scopes ());
 179        !i.is_done ();
 180        i.next ())
 181     {
 182       s = i.item ();
 183
 184       // If we hit a NULL we're done since it means that we're nested inside
 185       // a sequence, where recursive types may be used.
 186       if (s == 0)
 187         {
 188           return false;  // NOT ILLEGAL.
 189         }
 190
 191       // OK, must check this scope.
 192       if (s->scope_node_type () == AST_Decl::NT_struct
 193           && check_for_struct == true)
 194         {
 195           st2 = dynamic_cast<AST_Structure*> (s);
 196
 197           if (st2 != 0 && st2 == st1)
 198             {
 199               return true;  // ILLEGAL RECURSIVE TYPE USE.
 200             }
 201         }
 202       else if (s->scope_node_type () == AST_Decl::NT_union
 203                && check_for_union == true)
 204         {
 205           un2 = dynamic_cast<AST_Union*> (s);
 206
 207           if (un2 != 0 && un2 == un1)
 208             {
 209               return true;  // ILLEGAL RECURSIVE TYPE USE.
 210             }
 211         }
 212     }
 213
 214   // No more scopes to check. This type was used legally.
 215   return false;    // NOT ILLEGAL.
 216 }
 217