cpp_typecheck_bases.cpp

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/*******************************************************************\
 
Module: C++ Language Type Checking
 
Author: Daniel Kroening, kroening@cs.cmu.edu
 
\*******************************************************************/
 
 
#include "cpp_typecheck.h"
 
#include <set>
 
#include "cpp_typecheck_fargs.h"
 
void cpp_typecheckt::typecheck_compound_bases(struct_typet &type)
{
  std::set<irep_idt> bases;
  std::set<irep_idt> vbases;
 
  irep_idt default_class_access = type.default_access();
 
  irept::subt &bases_irep=type.add(ID_bases).get_sub();
 
  for(auto &base : bases_irep)
  {
    const cpp_namet &name = to_cpp_name(base.find(ID_name));
 
    exprt base_symbol_expr=
      resolve(
        name,
        cpp_typecheck_resolvet::wantt::TYPE,
        cpp_typecheck_fargst());
 
    if(base_symbol_expr.id()!=ID_type)
    {
      error().source_location=name.source_location();
      error() << "expected type as struct/class base" << eom;
      throw 0;
    }
 
    // elaborate any class template instances given as bases
    elaborate_class_template(base_symbol_expr.type());
 
    if(base_symbol_expr.type().id() != ID_struct_tag)
    {
      error().source_location=name.source_location();
      error() << "expected type symbol as struct/class base" << eom;
      throw 0;
    }
 
    const symbolt &base_symbol =
      lookup(to_struct_tag_type(base_symbol_expr.type()));
 
    if(base_symbol.type.id() != ID_struct)
    {
      error().source_location=name.source_location();
      error() << "expected struct or class as base, but got '"
              << to_string(base_symbol.type) << "'" << eom;
      throw 0;
    }
 
    if(to_struct_type(base_symbol.type).is_incomplete())
    {
      error().source_location=name.source_location();
      error() << "base type is incomplete" << eom;
      throw 0;
    }
 
    bool virtual_base = base.get_bool(ID_virtual);
    irep_idt class_access = base.get(ID_protection);
 
    if(class_access.empty())
      class_access = default_class_access;
 
    base_symbol_expr.id(ID_base);
    base_symbol_expr.set(ID_access, class_access);
 
    if(virtual_base)
      base_symbol_expr.set(ID_virtual, true);
 
    base.swap(base_symbol_expr);
 
    // Add base scopes as parents to the current scope
    cpp_scopes.current_scope().add_secondary_scope(
      static_cast<cpp_scopet &>(*cpp_scopes.id_map[base_symbol.name]));
 
    const struct_typet &base_struct_type=
      to_struct_type(base_symbol.type);
 
    add_base_components(
      base_struct_type,
      class_access,
      type,
      bases,
      vbases,
      virtual_base);
  }
 
  if(!vbases.empty())
  {
    // add a flag to determine
    // if this is the most-derived-object
    struct_typet::componentt most_derived(
      cpp_scopes.current_scope().prefix + "::" + "@most_derived", bool_typet());
 
    most_derived.set_access(ID_public);
    most_derived.set_base_name("@most_derived");
    most_derived.set_pretty_name("@most_derived");
    most_derived.add_source_location()=type.source_location();
    put_compound_into_scope(most_derived);
 
    to_struct_type(type).components().push_back(most_derived);
  }
}
 
void cpp_typecheckt::add_base_components(
  const struct_typet &from,
  const irep_idt &access,
  struct_typet &to,
  std::set<irep_idt> &bases,
  std::set<irep_idt> &vbases,
  bool is_virtual)
{
  const irep_idt &from_name = from.get(ID_name);
 
  if(is_virtual && vbases.find(from_name)!=vbases.end())
    return;
 
  if(bases.find(from_name)!=bases.end())
  {
    error().source_location=to.source_location();
    error() << "non-virtual base class " << from_name
            << " inherited multiple times" << eom;
    throw 0;
  }
 
  bases.insert(from_name);
 
  if(is_virtual)
    vbases.insert(from_name);
 
  // look at the the parents of the base type
  for(const auto &b : from.bases())
  {
    irep_idt sub_access = b.get(ID_access);
 
    if(access==ID_private)
      sub_access=ID_private;
    else if(access==ID_protected && sub_access!=ID_private)
      sub_access=ID_protected;
 
    const symbolt &symb = lookup(b.type());
 
    const bool is_virtual_base = b.get_bool(ID_virtual);
 
    // recursive call
    add_base_components(
      to_struct_type(symb.type),
      sub_access,
      to,
      bases,
      vbases,
      is_virtual_base);
  }
 
  // add the components
  struct_typet::componentst &dest_c=to.components();
 
  for(const auto &c : from.components())
  {
    if(c.get_bool(ID_from_base))
      continue;
 
    // copy the component
    dest_c.push_back(c);
 
    // now twiddle the copy
    struct_typet::componentt &component=dest_c.back();
    component.set(ID_from_base, true);
 
    irep_idt comp_access=component.get_access();
 
    if(access==ID_public)
    {
      if(comp_access==ID_private)
        component.set_access(ID_noaccess);
    }
    else if(access == ID_protected)
    {
      if(comp_access==ID_private)
        component.set_access(ID_noaccess);
      else
        component.set_access(ID_private);
    }
    else if(access == ID_private)
    {
      if(comp_access == ID_noaccess || comp_access == ID_private)
        component.set_access(ID_noaccess);
      else
        component.set_access(ID_private);
    }
    else
      UNREACHABLE;
 
    // put into scope
  }
}