todo

早期freebsd实现

Must eliminate use of stdio.h; that loses when using GNU libc.
(It is ok to include stdio.h only when debugging,
 for the sake of DEBUG_PRINTF.)
Can this be done?  If not, how do we make this work?

Eliminate the asserts in record.h.

Rename the global functions in core.c to GNU-style names;
 fix object.m at same time.


It is undesirable to use statics variables such as errorStatic in
handleRuntimeError--as dennisg noted.  Do programs depend on error
handling to be compatible with what it is on the NeXT?

For example, would it be ok for DoesNotRecognize to return
a method to be called, rather than a value to be returned?

If that is not ok, I have other ideas, but they are harder to
implement.



Why does dennisg say that object_getIvarAddress is not thread-safe?



objc_msgSend can be faster.
1. Delete the statement  if (!theReceiver->isa).
Instead, set the isa field of a deallocated object
to point to a dummy class called "deallocated".
This class should have a vector of operations
at least as long as any class has had during this execution.
Every element of this vector should point to `abort'.
Don't bother to print a fancy message; that is a waste of effort.
For something impossible, abort is *exactly* the right thing to do.
2. Is it really necessary to call initializeClass here?
Can't it be done in __objc_execClass, as soon as the class
is complete?  If you can avoid doing this here, that is
one fewer statement to execute.
3. Get rid of objc_trace.
4. Don't check wether getIMP returns null.
There should never be a null in the method vector.
If the method is not defined, store in the vector
a fake method that will print the appropriate error.
With these changes, all you need is this:
  if (theReceiver)
    return getIMP (theReceiver->isa, aSel);
  else
    return nilMethodIMP;
which is something that could plausibly be open-coded in the future.