Re: Bug report: objc classes linked in wrong order

[nicola at brainstorm dot co dot uk]

>   > Can I make an objective-C class weak ?
> I can't think of a reason why that wouldn't work.


>   > I found no evidence of this - because each module has a list of classes to
>   > load, and loads them all - but I might be wrong - so please give me a hint
>   > if I actually can in some way make a class weak.


> But they are "loaded" by the linker by including them in the final
> executable, right?  If so, at the .s/.o level you make the appropriate
> function(s) weak, then you should be OK.

Uhm - hope you are right :-) - that would be nice if we could
have 'weak' classes.
To me it looks difficult because my understanding of it is as follows:

[from libobjc/init.c]

/* This function is called by constructor functions generated for each
   module compiled.  (_GLOBAL_$I$...) The purpose of this function is to
   gather the module pointers so that they may be processed by the
   initialization routines as soon as possible */

void
__objc_exec_class (Module_t module)

So, the constructor functions contain a call of this function for each
module that gets loaded (they indeed do).  The module is represented by a
structure, created at compile time [defined in libobjc/objc/objc-api.h].
A pointer to this structure is passed as argument to __objc_exec_class ().
__objc_exec_class () accesses the members of the module structure
getting the list of selectors and classes to register.
It accesses the list of classes as follows:

loop on i
{
  Class class = (Class) module->symtab->defs[i];
  ...
}

which returns a structure containing the information needed to register
the new class with the runtime.

I can't see any function or symbol we could make weak.
Making __objc_exec_class weak is not what we want - that function is
global.  The classes to load are got accessing directly the pointer passed
as argument of __objc_exec_class - don't see what we can make weak here.


Any idea ?

Thanks for discussing - that helps a lot - sorry if I miss some basic
point.