Re: [patch] fix for c++/2416

[Aleksandar Ristovski <ARistovski at qnx dot com>]

Daniel Jacobowitz wrote:
> On Thu, Feb 28, 2008 at 11:45:07PM -0500, Aleksandar Ristovski wrote:
>> Allright, then how about this, yet newer and yet more revisited diff? I 
>> removed changes to eval.c and let it simply call value_cast as it used
to. 
>> Now value_cast knows how to handle references.
> 
> We were converging on a fix and then there's a whole different patch
> to look at... sorry I couldn't make time until now.
> 
>> @@ -257,6 +290,7 @@ value_cast_pointers (struct type *type, 
>>    return arg2;
>>  }
>>  
>> +
>>  /* Cast value ARG2 to type TYPE and return as a value.
>>     More general than a C cast: accepts any two types of the same length,
>>     and if ARG2 is an lvalue it can be cast into anything at all.  */
> 
> Please drop the whitespace change.
> 
>> @@ -275,6 +309,26 @@ value_cast (struct type *type, struct va
>>    if (value_type (arg2) == type)
>>      return arg2;
>>  
>> +  code1 = TYPE_CODE (check_typedef (type));
>> +
>> +  /* Check if we are casting struct reference to struct reference.  */
>> +  if (code1 == TYPE_CODE_REF)
>> +    {
>> +      /* We dereference type; then we recurse and finally
>> +         we generate value of the given reference. Nothing wrong with 
>> +	 that.  */
>> +      struct type *t1 = check_typedef (type);
>> +      struct type *dereftype = check_typedef (TYPE_TARGET_TYPE (t1));
>> +      struct value *val =  value_cast (dereftype, arg2);
>> +      return value_ref (val); 
>> +    }
> 
> This allows things like "(int&) int_var", by automatically creating
> references.  Should we really do that?
> 

I believe we should.

Here is a dummy c++ program where this is done explicitly:

#include <iostream>
using namespace std;
int main ()
{
   int a = 42;
   int &refa = (int &)a; // cast not needed, yet compiler doesn't complain.
   cout << refa << endl;
   return 0;
}