sendmsg.c

gcc的组件

/* GNU Objective C Runtime message lookup 
   Copyright (C) 1993, 1995, 1996, 1997, 1998,
   2001, 2002, 2004 Free Software Foundation, Inc.
   Contributed by Kresten Krab Thorup

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2, or (at your option) any later version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
details.

You should have received a copy of the GNU General Public License along with
GCC; see the file COPYING.  If not, write to the Free Software
Foundation, 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */

/* As a special exception, if you link this library with files compiled with
   GCC to produce an executable, this does not cause the resulting executable
   to be covered by the GNU General Public License. This exception does not
   however invalidate any other reasons why the executable file might be
   covered by the GNU General Public License.  */

/* FIXME: This file has no business including tm.h.  */
/* FIXME: This should be using libffi instead of __builtin_apply
   and friends.  */

#include "tconfig.h"
#include "coretypes.h"
#include "tm.h"
#include "objc/runtime.h"
#include "objc/sarray.h"
#include "objc/encoding.h"
#include "runtime-info.h"

/* This is how we hack STRUCT_VALUE to be 1 or 0.   */
#define gen_rtx(args...) 1
#define gen_rtx_MEM(args...) 1
#define gen_rtx_REG(args...) 1
#define rtx int

#if ! defined (STRUCT_VALUE) || STRUCT_VALUE == 0
#define INVISIBLE_STRUCT_RETURN 1
#else
#define INVISIBLE_STRUCT_RETURN 0
#endif

/* The uninstalled dispatch table */
struct sarray *__objc_uninstalled_dtable = 0;   /* !T:MUTEX */

/* Hook for method forwarding. If it is set, is invoked to return a
   function that performs the real forwarding. Otherwise the libgcc
   based functions (__builtin_apply and friends) are used. */
IMP (*__objc_msg_forward) (SEL) = NULL;

/* Send +initialize to class */
static void __objc_send_initialize (Class);

static void __objc_install_dispatch_table_for_class (Class);

/* Forward declare some functions */
static void __objc_init_install_dtable (id, SEL);

/* Various forwarding functions that are used based upon the
   return type for the selector.
   __objc_block_forward for structures.
   __objc_double_forward for floats/doubles.
   __objc_word_forward for pointers or types that fit in registers.
   */
static double __objc_double_forward (id, SEL, ...);
static id __objc_word_forward (id, SEL, ...);
typedef struct { id many[8]; } __big;
#if INVISIBLE_STRUCT_RETURN 
static __big 
#else
static id
#endif
__objc_block_forward (id, SEL, ...);
static Method_t search_for_method_in_hierarchy (Class class, SEL sel);
Method_t search_for_method_in_list (MethodList_t list, SEL op);
id nil_method (id, SEL);

/* Given a selector, return the proper forwarding implementation. */
inline
IMP
__objc_get_forward_imp (SEL sel)
{
  /* If a custom forwarding hook was registered, try getting a forwarding
   * function from it.  */
  if (__objc_msg_forward)
    {
      IMP result;
      if ((result = __objc_msg_forward (sel)) != NULL) 
        return result;
    }

  /* In all other cases, use the default forwarding functions built using
   * __builtin_apply and friends.  */
    {
      const char *t = sel->sel_types;

      if (t && (*t == '[' || *t == '(' || *t == '{')
#ifdef OBJC_MAX_STRUCT_BY_VALUE
          && objc_sizeof_type (t) > OBJC_MAX_STRUCT_BY_VALUE
#endif
          )
        return (IMP)__objc_block_forward;
      else if (t && (*t == 'f' || *t == 'd'))
        return (IMP)__objc_double_forward;
      else
        return (IMP)__objc_word_forward;
    }
}

/* Given a class and selector, return the selector's implementation.  */
inline
IMP
get_imp (Class class, SEL sel)
{
  /* In a vanilla implementation we would first check if the dispatch
     table is installed.  Here instead, to get more speed in the
     standard case (that the dispatch table is installed) we first try
     to get the imp using brute force.  Only if that fails, we do what
     we should have been doing from the very beginning, that is, check
     if the dispatch table needs to be installed, install it if it's
     not installed, and retrieve the imp from the table if it's
     installed.  */
  void *res = sarray_get_safe (class->dtable, (size_t) sel->sel_id);
  if (res == 0)
    {
      /* Not a valid method */
      if (class->dtable == __objc_uninstalled_dtable)
	{
	  /* The dispatch table needs to be installed. */
	  objc_mutex_lock (__objc_runtime_mutex);

	   /* Double-checked locking pattern: Check
	      __objc_uninstalled_dtable again in case another thread
	      installed the dtable while we were waiting for the lock
	      to be released.  */
         if (class->dtable == __objc_uninstalled_dtable)
           {
             __objc_install_dispatch_table_for_class (class);
           }

	  objc_mutex_unlock (__objc_runtime_mutex);
	  /* Call ourselves with the installed dispatch table
	     and get the real method */
	  res = get_imp (class, sel);
	}
      else
	{
	  /* The dispatch table has been installed.  */

         /* Get the method from the dispatch table (we try to get it
	    again in case another thread has installed the dtable just
	    after we invoked sarray_get_safe, but before we checked
	    class->dtable == __objc_uninstalled_dtable).
         */
	  res = sarray_get_safe (class->dtable, (size_t) sel->sel_id);
	  if (res == 0)
	    {
	      /* The dispatch table has been installed, and the method
		 is not in the dispatch table.  So the method just
		 doesn't exist for the class.  Return the forwarding
		 implementation. */
	      res = __objc_get_forward_imp (sel);
	    }
	}
    }
  return res;
}

/* Query if an object can respond to a selector, returns YES if the
object implements the selector otherwise NO.  Does not check if the
method can be forwarded. */
inline
BOOL
__objc_responds_to (id object, SEL sel)
{
  void *res;

  /* Install dispatch table if need be */
  if (object->class_pointer->dtable == __objc_uninstalled_dtable)
    {
      objc_mutex_lock (__objc_runtime_mutex);
      if (object->class_pointer->dtable == __objc_uninstalled_dtable)
	{
	  __objc_install_dispatch_table_for_class (object->class_pointer);
	}
      objc_mutex_unlock (__objc_runtime_mutex);
    }

  /* Get the method from the dispatch table */
  res = sarray_get_safe (object->class_pointer->dtable, (size_t) sel->sel_id);
  return (res != 0);
}

/* This is the lookup function.  All entries in the table are either a 
   valid method *or* zero.  If zero then either the dispatch table
   needs to be installed or it doesn't exist and forwarding is attempted. */
inline
IMP
objc_msg_lookup (id receiver, SEL op)
{
  IMP result;
  if (receiver)
    {
      result = sarray_get_safe (receiver->class_pointer->dtable, 
				(sidx)op->sel_id);
      if (result == 0)
	{
	  /* Not a valid method */
	  if (receiver->class_pointer->dtable == __objc_uninstalled_dtable)
	    {
	      /* The dispatch table needs to be installed.
		 This happens on the very first method call to the class. */
	      __objc_init_install_dtable (receiver, op);

	      /* Get real method for this in newly installed dtable */
	      result = get_imp (receiver->class_pointer, op);
	    }
	  else
	    {
	      /* The dispatch table has been installed.  Check again
		 if the method exists (just in case the dispatch table
		 has been installed by another thread after we did the
		 previous check that the method exists).
	      */
	      result = sarray_get_safe (receiver->class_pointer->dtable,
					(sidx)op->sel_id);
	      if (result == 0)
		{
		  /* If the method still just doesn't exist for the
		     class, attempt to forward the method. */
		  result = __objc_get_forward_imp (op);
		}
	    }
	}
      return result;
    }
  else
    return (IMP)nil_method;
}

IMP
objc_msg_lookup_super (Super_t super, SEL sel)
{
  if (super->self)
    return get_imp (super->class, sel);
  else
    return (IMP)nil_method;
}

int method_get_sizeof_arguments (Method *);

retval_t
objc_msg_sendv (id object, SEL op, arglist_t arg_frame)
{
  Method *m = class_get_instance_method (object->class_pointer, op);
  const char *type;
  *((id *) method_get_first_argument (m, arg_frame, &type)) = object;
  *((SEL *) method_get_next_argument (arg_frame, &type)) = op;
  return __builtin_apply ((apply_t) m->method_imp, 
			  arg_frame,
			  method_get_sizeof_arguments (m));
}

void
__objc_init_dispatch_tables ()
{
  __objc_uninstalled_dtable = sarray_new (200, 0);
}

/* This function is called by objc_msg_lookup when the
   dispatch table needs to be installed; thus it is called once
   for each class, namely when the very first message is sent to it. */
static void
__objc_init_install_dtable (id receiver, SEL op __attribute__ ((__unused__)))
{
  objc_mutex_lock (__objc_runtime_mutex);
  
  /* This may happen, if the programmer has taken the address of a 
     method before the dtable was initialized... too bad for him! */
  if (receiver->class_pointer->dtable != __objc_uninstalled_dtable)
    {
      objc_mutex_unlock (__objc_runtime_mutex);
      return;
    }
  
  if (CLS_ISCLASS (receiver->class_pointer))
    {
      /* receiver is an ordinary object */
      assert (CLS_ISCLASS (receiver->class_pointer));

      /* install instance methods table */
      __objc_install_dispatch_table_for_class (receiver->class_pointer);

      /* call +initialize -- this will in turn install the factory 
	 dispatch table if not already done :-) */
      __objc_send_initialize (receiver->class_pointer);
    }
  else
    {
      /* receiver is a class object */
      assert (CLS_ISCLASS ((Class)receiver));
      assert (CLS_ISMETA (receiver->class_pointer));

      /* Install real dtable for factory methods */
      __objc_install_dispatch_table_for_class (receiver->class_pointer);

      __objc_send_initialize ((Class)receiver);
    }
  objc_mutex_unlock (__objc_runtime_mutex);
}

/* Install dummy table for class which causes the first message to
   that class (or instances hereof) to be initialized properly */
void
__objc_install_premature_dtable (Class class)
{
  assert (__objc_uninstalled_dtable);
  class->dtable = __objc_uninstalled_dtable;
}   

/* Send +initialize to class if not already done */
static void
__objc_send_initialize (Class class)
{
  /* This *must* be a class object */
  assert (CLS_ISCLASS (class));
  assert (! CLS_ISMETA (class));

  if (! CLS_ISINITIALIZED (class))
    {
      CLS_SETINITIALIZED (class);
      CLS_SETINITIALIZED (class->class_pointer);

      /* Create the garbage collector type memory description */
      __objc_generate_gc_type_description (class);

      if (class->super_class)
	__objc_send_initialize (class->super_class);

      {
	SEL 	     op = sel_register_name ("initialize");
	IMP	     imp = 0;