Re: [bug #62147] Expanded classes not printable

[Paolo Redælli]

I'm quite puzzled by this issue so I think it is better to discuss it in 
the mailinst list.

See the recently committed test/language/expanded/test_expanded42.e

class TEST_EXPANDED42 -- Try to print an ARRAY of expanded values
insert EIFFELTEST_TOOLS redefine default_create end
create {ANY} default_create -- make
feature {ANY}
   default_create
      local foo, bar: AUX_EXPANDED40_EXP -- an empty expanded class
      do
         (<< foo, bar >> ).print_on(io)
         io.put_new_line
      end
end -- class TEST_EXP_ARRAY

expanded class AUX_EXPANDED40_EXP
-- empty class
end -- class AUX_EXPANDED40_EXP

It triggers a compile error in ANY, specifically in

out_in_tagged_out_memory
         -- Append terse printable representation of current object in 
`tagged_out_memory'.
      require
         locked: tagged_out_locked
      local
         like_current: like Current
      do
         tagged_out_memory.append(generating_type)
>>>>>HERE         if like_current = Void then
            -- Not an expanded type:
            tagged_out_memory.extend('#')
            to_pointer.append_in(tagged_out_memory)
         end
         tagged_out_memory.extend('[')
         fill_tagged_out_memory
         tagged_out_memory.extend(']')
      end

because an expanded class could never be compared to Void, which is the 
default reference (aka NULL for people accostumed to C). That piece of 
code prints the address (pointer) of the object.

The compiler is right - Void does not conform to any expanded object 
which are compared by value and not by reference.

I see three scenario:

1) we remove the feature altogether from ANY.

2) we keep it for reference objects but then ANY should have some 
external "built_in" features such as is_reference:BOOLEAN and 
is_expanded: BOOLEAN

3) we want to print the address of each and every object, even expanded 
one, so there must be a a function in the runtime but I fear it will be 
far from simple to implement.

I was going to naïvely follow scenario 1, but then I recalled that some 
people may rely on the output of the address...

To be truly earnest I thought that this issue is the remnant of some 
silly commit of mine, but as far as I can say it has been like this at 
least since adler-rc1 release (2009).

I wonder how such a issue has never been encountered before. It seems 
that people do not print expanded classes.



Il 07/03/22 11:55, Paolo Redaelli ha scritto:
> URL:
>    <https://savannah.gnu.org/bugs/?62147>
>
>                   Summary: Expanded classes not printable
>                   Project: Liberty Eiffel
>              Submitted by: Tybor
>              Submitted on: Mon 07 Mar 2022 10:55:49 AM UTC
>                  Category: Kernel libraries
>                  Severity: 4 - Important
>                  Priority: 5 - Normal
>                    Status: Need Info
>               Assigned to: None
>               Open/Closed: Open
>                   Release: None
>           Discussion Lock: Any
>             Fixed Release: None
>           Planned Release: None
>
>      _______________________________________________________
>
> Details:
>
> Let's have an
> expanded class FOO
>    -- empty
> end
>
> Any try to print it out, either in a collection (an ARRAY) or stand alone
> strigger a compile time error such as:
>
> ****** Error: Invalid usage of feature `to_pointer' of class ANY. (The target
> which is of type AUX_EXPANDED40_EXP cannot be converted to a memory address.)
>
> The source lines relevant to this message are the following:
>
> Line 284 column 13 in ANY
> (/home/paolo/src/liberty-eiffel/src/lib/kernel/any.e):
>              to_pointer.append_in(tagged_out_memory)
>              ^
> Line 421 column 4 in ANY
> (/home/paolo/src/liberty-eiffel/src/lib/kernel/any.e):
>     to_pointer: POINTER
>
>
>
>
>
>      _______________________________________________________
>
> Reply to this item at:
>
>    <https://savannah.gnu.org/bugs/?62147>
>
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