reicast.md

reinterpret_cast

Context menu "reinterpret_cast... (I)" and "Remove reinterpret_cast (I)"

For expressions like: "x + n", "x[n]", "x->member", "*x" where x is any sub-expression and n is a number, you may temporary, without changing variable type, force reinterpret typecast of x subexpression. Just press "I" and select appropriate structure pointer type of x sub-expression. The expression will be replaced to (reinterpret_cast<struct*>x)->struc_member

This trick may be helpful in following cases:

• reinterpret_cast was used in original source code
• optimizing compiler reuses local variable with different types
• to select right class's virtual table structure for inherited class's virtual call

For example, below is the procedure uses different types of stValue->value depending on a case of switch statement:

void __thiscall destroy_struct_value(struct_value *stValue)
{
  struct_value *stValue_1; // esi
  void *value; // edi
  struct_buffer *buf; // ecx
 
  stValue_1 = stValue;
  switch ( stValue->value_type )
  {
    case 0:
      goto LABEL_13;
    case 1:
      destroy_value_type_1((struct_value_type1 *)stValue->value);
      break;
    case 2:
      destroy_value_type_2((struct_value_type2 *)stValue->value);
      break;
    case 3:
      value = stValue->value;
      if ( !*((_DWORD *)value + 1) )
        *((_DWORD *)value + 1) = 1;
      if ( *(_DWORD *)value )
        free(*(void **)value);
      goto LABEL_17;
    default:
      if ( stValue->value_type != 4 )
        exit(1);
LABEL_13:
      value = stValue->value;
      if ( !*((_DWORD *)value + 2) )
        *((_DWORD *)value + 2) = 1;
      buf = (struct_buffer *)*((_DWORD *)value + 1);
      if ( buf )
        destroy_buffer(buf);
LABEL_17:
      free(value);
      break;
  }
  free(stValue_1);
}

After applying reinterpret_casts:

void __thiscall destroy_struct_value(struct_value *stValue)
{
  struct_value *stValue_1; // esi
  void *value; // edi
  struct_buffer *buf; // ecx
 
  stValue_1 = stValue;
  switch ( stValue->value_type )
  {
    case 0:
      goto LABEL_13;
    case 1:
      destroy_value_type_1((struct_value_type1 *)stValue->value);
      break;
    case 2:
      destroy_value_type_2((struct_value_type2 *)stValue->value);
      break;
    case 3:
      value = stValue->value;
      if ( !reinterpret_cast<struct_value_type3*>(value)->empty )
        reinterpret_cast<struct_value_type3*>(value)->empty = 1;
      if ( reinterpret_cast<struct_value_type3*>(value)->allocated_buffer )
        free(reinterpret_cast<struct_value_type3*>(value)->allocated_buffer);
      goto LABEL_17;
    default:
      if ( stValue->value_type != 4 )
        exit(1);
LABEL_13:
      value = stValue->value;
      if ( !reinterpret_cast<struct_value_type4*>(value)->empty )
        reinterpret_cast<struct_value_type4*>(value)->empty = 1;
      buf = reinterpret_cast<struct_value_type4*>(value)->buf;
      if ( buf )
        destroy_buffer(buf);
LABEL_17:
      free(value);
      break;
  }
  free(stValue_1);
}