cpp_typecheck_code.cpp

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/*******************************************************************\
 
Module: C++ Language Type Checking
 
Author: Daniel Kroening, kroening@cs.cmu.edu
 
\*******************************************************************/
 
 
#include <util/arith_tools.h>
#include <util/bitvector_expr.h>
#include <util/c_types.h>
#include <util/pointer_expr.h>
#include <util/source_location.h>
 
#include "cpp_declarator_converter.h"
#include "cpp_exception_id.h"
#include "cpp_typecheck.h"
#include "cpp_typecheck_fargs.h"
#include "cpp_util.h"
 
void cpp_typecheckt::typecheck_code(codet &code)
{
  const irep_idt &statement=code.get_statement();
 
  if(statement==ID_try_catch)
  {
    code.type() = empty_typet();
    typecheck_try_catch(code);
  }
  else if(statement==ID_member_initializer)
  {
    code.type() = empty_typet();
    typecheck_member_initializer(code);
  }
  else if(statement==ID_msc_if_exists ||
          statement==ID_msc_if_not_exists)
  {
  }
  else if(statement==ID_decl_block)
  {
    // type checked already
  }
  else if(statement == ID_expression)
  {
    if(
      !code.has_operands() || code.op0().id() != ID_side_effect ||
      to_side_effect_expr(code.op0()).get_statement() != ID_assign)
    {
      c_typecheck_baset::typecheck_code(code);
      return;
    }
 
    // as an extension, we support indexed access into signed/unsigned
    // bitvectors, typically used with __CPROVER::(un)signedbv<N>
    exprt &expr = code.op0();
 
    if(expr.operands().size() == 2)
    {
      auto &binary_expr = to_binary_expr(expr);
 
      if(binary_expr.op0().id() == ID_index)
      {
        exprt array = to_index_expr(binary_expr.op0()).array();
        typecheck_expr(array);
 
        if(
          array.type().id() == ID_signedbv ||
          array.type().id() == ID_unsignedbv)
        {
          shl_exprt shl{from_integer(1, array.type()),
                        to_index_expr(binary_expr.op0()).index()};
          exprt rhs = if_exprt{
            equal_exprt{
              binary_expr.op1(), from_integer(0, binary_expr.op1().type())},
            bitand_exprt{array, bitnot_exprt{shl}},
            bitor_exprt{array, shl}};
          binary_expr.op0() = to_index_expr(binary_expr.op0()).array();
          binary_expr.op1() = rhs;
        }
      }
    }
 
    c_typecheck_baset::typecheck_code(code);
  }
  else
    c_typecheck_baset::typecheck_code(code);
}
 
void cpp_typecheckt::typecheck_try_catch(codet &code)
{
  bool first = true;
 
  for(auto &op : code.operands())
  {
    if(first)
    {
      // this is the 'try'
      typecheck_code(to_code(op));
      first = false;
    }
    else
    {
      // This is (one of) the catch clauses.
      code_blockt &catch_block = to_code_block(to_code(op));
 
      // look at the catch operand
      auto &statements = catch_block.statements();
      PRECONDITION(!statements.empty());
 
      if(statements.front().get_statement() == ID_ellipsis)
      {
        statements.erase(statements.begin());
 
        // do body
        typecheck_code(catch_block);
      }
      else
      {
        // turn references into non-references
        {
          code_frontend_declt &decl = to_code_frontend_decl(statements.front());
          cpp_declarationt &cpp_declaration = to_cpp_declaration(decl.symbol());
 
          PRECONDITION(cpp_declaration.declarators().size() == 1);
          cpp_declaratort &declarator=cpp_declaration.declarators().front();
 
          if(is_reference(declarator.type()))
            declarator.type() =
              to_reference_type(declarator.type()).base_type();
        }
 
        // typecheck the body
        typecheck_code(catch_block);
 
        // the declaration is now in a decl_block
        CHECK_RETURN(!catch_block.statements().empty());
        CHECK_RETURN(
          catch_block.statements().front().get_statement() == ID_decl_block);
 
        // get the declaration
        const code_frontend_declt &code_decl = to_code_frontend_decl(
          to_code(catch_block.statements().front().op0()));
 
        // get the type
        const typet &type = code_decl.symbol().type();
 
        // annotate exception ID
        op.set(ID_exception_id, cpp_exception_id(type, *this));
      }
    }
  }
}
 
void cpp_typecheckt::typecheck_ifthenelse(code_ifthenelset &code)
{
  // In addition to the C syntax, C++ also allows a declaration
  // as condition. E.g.,
  // if(void *p=...) ...
 
  if(code.cond().id()==ID_code)
  {
    typecheck_code(to_code(code.cond()));
  }
  else
    c_typecheck_baset::typecheck_ifthenelse(code);
}
 
void cpp_typecheckt::typecheck_while(code_whilet &code)
{
  // In addition to the C syntax, C++ also allows a declaration
  // as condition. E.g.,
  // while(void *p=...) ...
 
  if(code.cond().id()==ID_code)
  {
    typecheck_code(to_code(code.cond()));
  }
  else
    c_typecheck_baset::typecheck_while(code);
}
 
void cpp_typecheckt::typecheck_switch(codet &code)
{
  // In addition to the C syntax, C++ also allows a declaration
  // as condition. E.g.,
  // switch(int i=...) ...
 
  exprt &value = to_code_switch(code).value();
  if(value.id() == ID_code)
  {
    // we shall rewrite that into
    // { int i=....; switch(i) .... }
 
    codet decl = to_code(value);
    typecheck_decl(decl);
 
    CHECK_RETURN(decl.get_statement() == ID_decl_block);
    CHECK_RETURN(decl.operands().size() == 1);
 
    // replace declaration by its symbol
    value = to_code_frontend_decl(to_code(to_unary_expr(decl).op())).symbol();
 
    c_typecheck_baset::typecheck_switch(code);
 
    code_blockt code_block({to_code(decl.op0()), code});
    code.swap(code_block);
  }
  else
    c_typecheck_baset::typecheck_switch(code);
}
 
void cpp_typecheckt::typecheck_member_initializer(codet &code)
{
  const cpp_namet &member=
    to_cpp_name(code.find(ID_member));
 
  // Let's first typecheck the operands.
  Forall_operands(it, code)
  {
    const bool has_array_ini = it->get_bool(ID_C_array_ini);
    typecheck_expr(*it);
    if(has_array_ini)
      it->set(ID_C_array_ini, true);
  }
 
  // The initializer may be a data member (non-type)
  // or a parent class (type).
  // We ask for VAR only, as we get the parent classes via their
  // constructor!
  cpp_typecheck_fargst fargs;
  fargs.in_use=true;
  fargs.operands=code.operands();
 
  // We should only really resolve in qualified mode,
  // no need to look into the parent.
  // Plus, this should happen in class scope, not the scope of
  // the constructor because of the constructor arguments.
  exprt symbol_expr=
    resolve(member, cpp_typecheck_resolvet::wantt::VAR, fargs);
 
  if(symbol_expr.type().id()==ID_code)
  {
    const code_typet &code_type=to_code_type(symbol_expr.type());
 
    DATA_INVARIANT(
      code_type.parameters().size() >= 1, "at least one parameter");
 
    // It's a parent. Call the constructor that we got.
    side_effect_expr_function_callt function_call(
      symbol_expr, {}, uninitialized_typet{}, code.source_location());
    function_call.arguments().reserve(code.operands().size()+1);
 
    // we have to add 'this'
    exprt this_expr = cpp_scopes.current_scope().this_expr;
    PRECONDITION(this_expr.is_not_nil());
 
    make_ptr_typecast(
      this_expr, to_pointer_type(code_type.parameters().front().type()));
 
    function_call.arguments().push_back(this_expr);
 
    for(const auto &op : as_const(code).operands())
      function_call.arguments().push_back(op);
 
    // done building the expression, check the argument types
    typecheck_function_call_arguments(function_call);
 
    if(symbol_expr.get_bool(ID_C_not_accessible))
    {
      const irep_idt &access = symbol_expr.get(ID_C_access);
      CHECK_RETURN(
        access == ID_private || access == ID_protected ||
        access == ID_noaccess);
 
      if(access == ID_private || access == ID_noaccess)
      {
        #if 0
        error().source_location=code.find_source_location();
        error() << "constructor of '"
                << to_string(symbol_expr)
                << "' is not accessible" << eom;
        throw 0;
        #endif
      }
    }
 
    code_expressiont code_expression(function_call);
 
    code.swap(code_expression);
  }
  else
  {
    // a reference member
    if(
      symbol_expr.id() == ID_dereference &&
      to_dereference_expr(symbol_expr).pointer().id() == ID_member &&
      symbol_expr.get_bool(ID_C_implicit))
    {
      // treat references as normal pointers
      exprt tmp = to_dereference_expr(symbol_expr).pointer();
      symbol_expr.swap(tmp);
    }
 
    if(symbol_expr.id() == ID_symbol &&
       symbol_expr.type().id()!=ID_code)
    {
      // maybe the name of the member collides with a parameter of the
      // constructor
      exprt dereference(
        ID_dereference,
        to_pointer_type(cpp_scopes.current_scope().this_expr.type())
          .base_type());
      dereference.copy_to_operands(cpp_scopes.current_scope().this_expr);
      cpp_typecheck_fargst deref_fargs;
      deref_fargs.add_object(dereference);
 
      {
        cpp_save_scopet cpp_saved_scope(cpp_scopes);
        cpp_scopes.go_to(
          *(cpp_scopes.id_map[cpp_scopes.current_scope().class_identifier]));
        symbol_expr =
          resolve(member, cpp_typecheck_resolvet::wantt::VAR, deref_fargs);
      }
 
      if(
        symbol_expr.id() == ID_dereference &&
        to_dereference_expr(symbol_expr).pointer().id() == ID_member &&
        symbol_expr.get_bool(ID_C_implicit))
      {
        // treat references as normal pointers
        exprt tmp = to_dereference_expr(symbol_expr).pointer();
        symbol_expr.swap(tmp);
      }
    }
 
    if(
      symbol_expr.id() == ID_member &&
      to_member_expr(symbol_expr).op().id() == ID_dereference &&
      to_dereference_expr(to_member_expr(symbol_expr).op()).pointer() ==
        cpp_scopes.current_scope().this_expr)
    {
      if(is_reference(symbol_expr.type()))
      {
        // it's a reference member
        if(code.operands().size()!= 1)
        {
          error().source_location=code.find_source_location();
          error() << " reference '" << to_string(symbol_expr)
                  << "' expects one initializer" << eom;
          throw 0;
        }
 
        reference_initializer(
          code.op0(), to_reference_type(symbol_expr.type()));
 
        // assign the pointers
        symbol_expr.type().remove(ID_C_reference);
        symbol_expr.set(ID_C_lvalue, true);
        code.op0().type().remove(ID_C_reference);
 
        side_effect_exprt assign(
          ID_assign,
          {symbol_expr, code.op0()},
          typet(),
          code.source_location());
        typecheck_side_effect_assignment(assign);
        code_expressiont new_code(assign);
        code.swap(new_code);
      }
      else
      {
        // it's a data member
        already_typechecked_exprt::make_already_typechecked(symbol_expr);
 
        auto call =
          cpp_constructor(code.source_location(), symbol_expr, code.operands());
 
        if(call.has_value())
          code.swap(call.value());
        else
        {
          auto source_location = code.source_location();
          code = code_skipt();
          code.add_source_location() = source_location;
        }
      }
    }
    else
    {
      error().source_location=code.find_source_location();
      error() << "invalid member initializer '" << to_string(symbol_expr) << "'"
              << eom;
      throw 0;
    }
  }
}
 
void cpp_typecheckt::typecheck_decl(codet &code)
{
  if(code.operands().size()!=1)
  {
    error().source_location=code.find_source_location();
    error() << "declaration expected to have one operand" << eom;
    throw 0;
  }
 
  PRECONDITION(code.op0().id() == ID_cpp_declaration);
 
  cpp_declarationt &declaration=
    to_cpp_declaration(code.op0());
 
  typet &type=declaration.type();
 
  bool is_typedef=declaration.is_typedef();
 
  if(declaration.declarators().empty() || !has_auto(type))
    typecheck_type(type);
 
  CHECK_RETURN(type.is_not_nil());
 
  if(
    declaration.declarators().empty() &&
    ((type.id() == ID_struct_tag &&
      follow_tag(to_struct_tag_type(type)).get_bool(ID_C_is_anonymous)) ||
     (type.id() == ID_union_tag &&
      follow_tag(to_union_tag_type(type)).get_bool(ID_C_is_anonymous)) ||
     type.get_bool(ID_C_is_anonymous)))
  {
    if(type.id() != ID_union_tag)
    {
      error().source_location=code.find_source_location();
      error() << "declaration statement does not declare anything"
              << eom;
      throw 0;
    }
 
    code = convert_anonymous_union(declaration);
    return;
  }
 
  // mark as 'already typechecked'
  already_typechecked_typet::make_already_typechecked(type);
 
  codet new_code(ID_decl_block);
  new_code.reserve_operands(declaration.declarators().size());
 
  // Do the declarators (if any)
  for(auto &declarator : declaration.declarators())
  {
    cpp_declarator_convertert cpp_declarator_converter(*this);
    cpp_declarator_converter.is_typedef=is_typedef;
 
    const symbolt &symbol=
      cpp_declarator_converter.convert(declaration, declarator);
 
    if(is_typedef)
      continue;
 
    if(!symbol.is_type && !symbol.is_extern && symbol.type.id() == ID_empty)
    {
      error().source_location = symbol.location;
      error() << "void-typed symbol not permitted" << eom;
      throw 0;
    }
 
    code_frontend_declt decl_statement(cpp_symbol_expr(symbol));
    decl_statement.add_source_location()=symbol.location;
 
    // Do we have an initializer that's not code?
    if(symbol.value.is_not_nil() &&
       symbol.value.id()!=ID_code)
    {
      decl_statement.copy_to_operands(symbol.value);
      DATA_INVARIANT(
        has_auto(symbol.type) || decl_statement.op1().type() == symbol.type,
        "declarator type should match symbol type");
    }
 
    new_code.add_to_operands(std::move(decl_statement));
 
    // is there a constructor to be called?
    if(symbol.value.is_not_nil())
    {
      DATA_INVARIANT(
        declarator.find(ID_init_args).is_nil(),
        "declarator should not have init_args");
      if(symbol.value.id()==ID_code)
        new_code.copy_to_operands(symbol.value);
    }
    else
    {
      exprt object_expr=cpp_symbol_expr(symbol);
 
      already_typechecked_exprt::make_already_typechecked(object_expr);
 
      auto constructor_call = cpp_constructor(
        symbol.location, object_expr, declarator.init_args().operands());
 
      if(constructor_call.has_value())
        new_code.add_to_operands(std::move(constructor_call.value()));
    }
  }
 
  code.swap(new_code);
}
 
void cpp_typecheckt::typecheck_block(code_blockt &code)
{
  cpp_save_scopet saved_scope(cpp_scopes);
  cpp_scopes.new_block_scope();
 
  c_typecheck_baset::typecheck_block(code);
}