Re: Linker for OOP

["Mikiya Matsuzaka" <yoyu at tiara dot ocn dot ne dot jp>]

Somebody?

I think linker's native support for OOP is really good thing.

I have been thinking about Objective-C dialect.  I think Obj-C is
simple and good, and if its `@selector' takes two arguments, class
name and message name, then the method lookup mechanism is no more
necessary because it becomes just an offset to method table that
resolved in link phase.

Somebody respond please.


                            +----------------------------+
        FILE1.m          => |          File1.o           |
+-----------------------+    | +------------------------+ |
| RootClass             |    | |                        | |
| {                     |    | |                        | |
|     classMethod_1     |    | |                        | |
|     instanceMethod_1  | => | | 0                      | |
|     instanceMethod_2  | => | | 1                      | |
| }                     |    | |                        | |
|                       |    | | RootClassMAX           | |
|                       |    | |     => 2               | |
+-----------------------+    | +------------------------+ |
                            |                            |
                            |                            |
                            |                            |
        FILE2.m          => |          File2.o           |
+-----------------------+    | +------------------------+ |
| SubClass: RootClass   |    | |                        | |
| {                     |    | |                        | |
|     classMethod_2     |    | |                        | |
|     instanceMethod_3  | => | | RootClassMAX + 0       | |
|     instanceMethod_4  | => | | RootClassMAX + 1       | |
| }                     |    | |                        | |
|                       |    | | SubClassMAX            | |
|                       |    | |    => RootClassMAX + 2 | |
+-----------------------+    | +------------------------+ |
                            +----------------------------+
                                         ||
                                         \/

                                Metaclass {
                                    Class*  isa;
                                    IMP     method[] = {
                                        classMethod_1,
                                        classMethod_2
                                    };
                                }
                            
                                RootClass {
                                    Class*  isa;
                                    Class*  super;
                                    IMP     method[] = {
                                        instanceMethod_1,
                                        instanceMethod_2,
                                    };
                                }
                            
                                SubClass {
                                    Class*  isa;
                                    Class*  super;    
                                    IMP     method[] = {
                                        instanceMethod_1,
                                        instanceMethod_2,
                                        instanceMethod_3,
                                        instanceMethod_4,
                                    };
                                }

----- Original Message ----- 
From: "Mikiya Matsuzaka" <yoyu@tiara.ocn.ne.jp>
To: <binutils@sourceware.org>
Sent: Friday, September 01, 2006 8:37 AM
Subject: Linker for OOP


> I found this description in GCC Internals info file.
>
> ------------------------------------------------------------------------
>    11.7 Constant Expression Types
>    ==============================
>
>    ...
>
>    `(const:M EXP)'
>         Represents a constant that is the result of an assembly-time
>         arithmetic computation.  The operand, EXP, is an expression that
>         contains only constants (`const_int', `symbol_ref' and `label_ref'
>         expressions) combined with `plus' and `minus'.  However, not all
>         combinations are valid, since the assembler cannot do arbitrary
>         arithmetic on relocatable symbols.
>
>         M should be `Pmode'.
> ------------------------------------------------------------------------
>
> Are there any plan to implement this facility as an extension to
> object file format?
>
> I don't know the fact but I suppose why linker was originally
> invented was to promise user to recompile only modified .c files, 
> and this principal was broken with object oriented programming.
>
> I think with this facility, simple OO language will be much cleaner
> than the current, because the offset of member variables or method
> table are resolved in link phase.
>
> Please comment.
>
> ---
> Mikiya Matsuzaka