alignment_checks.cpp

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/*******************************************************************\
 
Module: Alignment Checks
 
Author:
 
\*******************************************************************/

 
#include "alignment_checks.h"
 
#include <util/config.h>
#include <util/namespace.h>
#include <util/pointer_offset_size.h>
#include <util/std_types.h>
#include <util/symbol_table_base.h>
 
#include <ostream>
 
void print_struct_alignment_problems(
  const symbol_table_baset &symbol_table,
  std::ostream &out)
{
  for(const auto &symbol_pair : symbol_table.symbols)
  {
    if(symbol_pair.second.is_type && symbol_pair.second.type.id() == ID_struct)
    {
      const struct_typet &str = to_struct_type(symbol_pair.second.type);
      const struct_typet::componentst &components = str.components();
 
      bool first_time_seen_in_struct = true;
 
      for(struct_typet::componentst::const_iterator it_mem = components.begin();
          it_mem != components.end();
          it_mem++)
      {
        mp_integer cumulated_length = 0;
        bool first_time_seen_from = true;
 
        // if the instruction cannot be aligned to the address,
        // try the next one
 
        if(it_mem->get_is_padding())
          // || alignment(it_mem->type())%config.ansi_c.alignment!=0)
          continue;
 
        for(struct_typet::componentst::const_iterator it_next = it_mem;
            it_next != components.end();
            it_next++)
        {
          const typet &it_type = it_next->type();
          const namespacet ns(symbol_table);
          auto size = pointer_offset_size(it_type, ns);
 
          if(!size.has_value())
            throw "type of unknown size:\n" + it_type.pretty();
 
          cumulated_length += *size;
          // [it_mem;it_next] cannot be covered by an instruction
          if(cumulated_length > config.ansi_c.memory_operand_size)
          {
            // if interferences have been found, no need to check with
            // starting from an already covered member
            if(!first_time_seen_from)
              it_mem = it_next - 1;
            break;
          }
 
          if(it_mem != it_next && !it_next->get_is_padding())
          {
            if(first_time_seen_in_struct)
            {
              first_time_seen_in_struct = false;
              first_time_seen_from = false;
 
              out << "\nWARNING: "
                  << "declaration of structure "
                  << str.find_type(ID_tag).pretty() << " at "
                  << symbol_pair.second.location << '\n';
            }
 
            out << "members " << it_mem->get_name() << " and "
                << it_next->get_name() << " might interfere\n";
          }
        }
      }
    }
    else if(symbol_pair.second.type.id() == ID_array)
    {
      // is this structure likely to introduce data races?
      #if 0
      const namespacet ns(symbol_table);
      const array_typet array=to_array_type(symbol_pair.second.type);
      const auto size=
        pointer_offset_size(array.subtype(), ns);
 
      if(!size.has_value())
        throw "type of unknown size:\n"+it_type.pretty();
 
      if(2*integer2long(*size)<=config.ansi_c.memory_operand_size)
      {
        out << "\nWARNING: "
            << "declaration of an array at "
            << symbol_pair.second.location <<
            << "\nmight be concurrently accessed\n";
      }
      #endif
    }
  }
}