Patchwork =?UTF-8?Q?libobjc=20-=20added=20objc=5FsetProperty=20and=20related?=

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Submitter Nicola Pero
Date Oct. 24, 2010, 5:24 p.m.
Message ID <1287941086.847228490@192.168.2.227>
Download mbox | patch
Permalink /patch/69044/
State New
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Comments

Nicola Pero - Oct. 24, 2010, 5:24 p.m.
This patch adds to the GNU Objective-C runtime the functions that will be required 
to implement synthesized Objective-C 2.0 property setters/getters.

There is one non-obvious thing I did - I added  objc_getPropertyStruct() 
and objc_setPropertyStruct().  The Apple runtime has the function objc_copyStruct() 
that requires two locks due to a mix-up in the design; for the GNU Objective-C runtime 
I added objc_copyStruct() but I also added two new functions, objc_getPropertyStruct() 
and objc_setPropertyStruct(), which only require one lock each, and I plan to have GCC 
use these (instead of objc_copyStruct()) when generating code for the GNU runtime. :-)

(My main concern with these new functions is the naming, to make sure they won't clash
with anything else that may be added by Apple in the future.  Suggestions for better names 
are welcome.)

All the functions in this patch are currently unused; the GCC compiler code that synthesizes 
the property setters/getters is still missing.  We may want/need to change or fix the functions as
we write the code.  Hopefully we'll manage to write that code in the next couple of days 
before the GCC stage 1 gates close. :-)

Committed to trunk.

Thanks

In libobjc/:
2010-10-24  Nicola Pero  <nicola.pero@meta-innovation.com>

        * Makefile.in (OBJC_SOURCE_FILES): Added accessors.m.
        * accessors.m: New.
        * init.c: Include objc-private/accessors.h.
        (__objc_exec_class): Call __objc_accessors_init.
        * objc-private/accessors.h: New.

Patch

Index: accessors.m
===================================================================
--- accessors.m	(revision 0)
+++ accessors.m	(revision 0)
@@ -0,0 +1,279 @@ 
+/* GNU Objective C Runtime accessors functions
+   Copyright (C) 2010 Free Software Foundation, Inc.
+   Contributed by Nicola Pero
+
+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 3, 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.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+#include "objc-private/common.h"
+#include "objc/objc.h"
+#include "objc/thr.h"
+#include <string.h>                    /* For memcpy */
+
+/* This file contains functions that the compiler uses when
+   synthesizing accessors (getters/setters) for properties.  The
+   functions are part of the ABI, but are meant to be used by the
+   compiler and not by users; for this reason, they are not declared
+   in public header files.  The compiler automatically generates
+   declarations for these functions.  */
+
+/* Properties can be "atomic", which requires protecting them from
+   concurrency issues using a lock.  Unfortunately, we can't have a
+   lock for each property, so we'll go with a small pool of locks.
+   Any time a property is accessed in an "atomic" way, we pick a
+   random lock from the pool (random, but always the same one for the
+   same property of the same object) and use it to protect access to
+   the property.
+
+   The size of the pool is currently 16.  A bigger pool can help
+   reduce contention, ie, reduce the chances that two threads,
+   operating on unrelated properties, will have to wait for each other
+   because the properties use the same lock.  16 seems big enough at
+   the moment.  */
+#define ACCESSORS_NUMBER_OF_LOCKS 16
+
+#define ACCESSORS_HASH(POINTER) ((((size_t)POINTER >> 8) ^ (size_t)POINTER) & (ACCESSORS_NUMBER_OF_LOCKS - 1))
+
+static objc_mutex_t accessors_locks[ACCESSORS_NUMBER_OF_LOCKS];
+
+/* This is called at startup to setup the locks.  */
+void
+__objc_accessors_init (void)
+{
+  int i;
+
+  for (i = 0; i < ACCESSORS_NUMBER_OF_LOCKS; i++)
+    accessors_locks[i] = objc_mutex_allocate ();
+}
+
+/* The property accessors automatically call various methods from the
+   Foundation library (eg, GNUstep-base).  These methods are not
+   implemented here, but we need to declare them so we can compile the
+   runtime.  The Foundation library will need to provide
+   implementations of these methods (most likely in the root class,
+   eg, NSObject) as the accessors only work with objects of classes
+   that implement these methods.  */
+@interface _libobjcNSObject
+- (id) copyWithZone: (void *)zone;
+- (id) mutableCopyWithZone: (void *)zone;
+@end
+#define COPY(X)         [((_libobjcNSObject *)(X)) copyWithZone: NULL]
+#define MUTABLE_COPY(X) [((_libobjcNSObject *)(X)) mutableCopyWithZone: NULL]
+
+
+#if OBJC_WITH_GC
+
+#  define AUTORELEASE(X)  (X)
+#  define RELEASE(X)
+#  define RETAIN(X)       (X)
+
+#else
+
+@interface _libobjcNSObject (RetainReleaseMethods)
+- (id) autorelease;
+- (oneway void) release;
+- (id) retain;
+@end
+#  define AUTORELEASE(X)  [((_libobjcNSObject *)(X)) autorelease]
+#  define RELEASE(X)      [((_libobjcNSObject *)(X)) release]
+#  define RETAIN(X)       [((_libobjcNSObject *)(X)) retain]
+
+#endif
+
+/* The compiler uses this function when implementing some synthesized
+   getters for properties of type 'id'.  */
+id
+objc_getProperty (id self, SEL __attribute__((unused)) _cmd, ptrdiff_t offset, BOOL is_atomic)
+{
+  if (self != nil)
+    {
+      id *pointer_to_ivar = (id *)((char *)self + offset);
+
+      if (is_atomic == NO)
+	return AUTORELEASE (RETAIN (*pointer_to_ivar));
+      else
+	{
+	  objc_mutex_t lock = accessors_locks[ACCESSORS_HASH (pointer_to_ivar)];
+	  id result;
+	  
+	  objc_mutex_lock (lock);
+	  result = RETAIN (*(pointer_to_ivar));
+	  objc_mutex_unlock (lock);
+	  
+	  return AUTORELEASE (result);
+	}
+    }
+
+  return nil;
+}
+
+/* The compiler uses this function when implementing some synthesized
+   setters for properties of type 'id'.
+
+   PS: Note how 'should_copy' is declared 'BOOL' but then actually
+   takes values from 0 to 2.  This hack was introduced by Apple; we
+   do the same for compatibility reasons.  */
+void
+objc_setProperty (id self, SEL __attribute__((unused)) _cmd, ptrdiff_t offset, id new_value, BOOL is_atomic, BOOL should_copy)
+{
+  if (self != nil)
+    {
+      id *pointer_to_ivar = (id *)((char *)self + offset);
+      id retained_value;
+#if !OBJC_WITH_GC
+      id old_value;
+#endif
+
+      switch (should_copy)
+	{
+	case 0: /* retain */
+	  {
+	    if (*pointer_to_ivar == new_value)
+	      return;
+	    retained_value = RETAIN (new_value);
+	    break;
+	  }
+	case 2: /* mutable copy */
+	  {
+	    retained_value = MUTABLE_COPY (new_value);
+	    break;
+	  }
+	case 1: /* copy */
+	default:
+	  {
+	    retained_value = COPY (new_value);
+	    break;
+	  }
+	}
+
+      if (is_atomic == NO)
+	{
+#if !OBJC_WITH_GC
+	  old_value = *pointer_to_ivar;
+#endif
+	  *pointer_to_ivar = retained_value;
+	}
+      else
+	{
+	  objc_mutex_t lock = accessors_locks[ACCESSORS_HASH (pointer_to_ivar)];
+
+	  objc_mutex_lock (lock);
+#if !OBJC_WITH_GC
+	  old_value = *pointer_to_ivar;
+#endif
+	  *pointer_to_ivar = retained_value;
+	  objc_mutex_unlock (lock);
+	}
+#if !OBJC_WITH_GC
+      RELEASE (old_value);
+#endif
+    }
+}
+
+/* The compiler uses this function when implementing some synthesized
+   getters for properties of arbitrary C types.  The data is just
+   copied.  Compatibility Note: this function does not exist in the
+   Apple/NeXT runtime.  */
+void
+objc_getPropertyStruct (void *destination, const void *source, ptrdiff_t size, BOOL is_atomic, BOOL __attribute__((unused)) has_strong)
+{
+  if (is_atomic == NO)
+    memcpy (destination, source, size);
+  else
+    {
+      objc_mutex_t lock = accessors_locks[ACCESSORS_HASH (source)];
+
+      objc_mutex_lock (lock);
+      memcpy (destination, source, size);
+      objc_mutex_unlock (lock);
+    }
+}
+
+/* The compiler uses this function when implementing some synthesized
+   setters for properties of arbitrary C types.  The data is just
+   copied.  Compatibility Note: this function does not exist in the
+   Apple/NeXT runtime.  */
+void
+objc_setPropertyStruct (void *destination, const void *source, ptrdiff_t size, BOOL is_atomic, BOOL __attribute__((unused)) has_strong)
+{
+  if (is_atomic == NO)
+    memcpy (destination, source, size);
+  else
+    {
+      objc_mutex_t lock = accessors_locks[ACCESSORS_HASH (destination)];
+
+      objc_mutex_lock (lock);
+      memcpy (destination, source, size);
+      objc_mutex_unlock (lock);
+    }
+}
+
+/* This is the function that the Apple/NeXT runtime has instead of
+   objc_getPropertyStruct and objc_setPropertyStruct.  We include it
+   for API compatibility (just for people who may have used
+   objc_copyStruct on the NeXT runtime thinking it was a public API);
+   the compiler never generates calls to it with the GNU runtime.
+   This function is clumsy because it requires two locks instead of
+   one.  */
+void
+objc_copyStruct (void *destination, const void *source, ptrdiff_t size, BOOL is_atomic, BOOL __attribute__((unused)) has_strong)
+{
+  if (is_atomic == NO)
+    memcpy (destination, source, size);
+  else
+    {
+      /* We don't know which one is the property, so we have to lock
+	 both.  One of them is most likely a temporary buffer in the
+	 local stack and we really wouldn't want to lock it (our
+	 objc_getPropertyStruct and objc_setPropertyStruct functions
+	 don't lock it).  Note that if we're locking more than one
+	 accessor lock at once, we need to always lock them in the
+	 same order to avoid deadlocks.  */
+      objc_mutex_t first_lock;
+      objc_mutex_t second_lock;
+
+      if (ACCESSORS_HASH (source) == ACCESSORS_HASH (destination))
+	{
+	  /* A lucky collision.  */
+	  first_lock = accessors_locks[ACCESSORS_HASH (source)];
+	  objc_mutex_lock (first_lock);
+	  memcpy (destination, source, size);
+	  objc_mutex_unlock (first_lock);
+	  return;
+	}
+
+      if (ACCESSORS_HASH (source) > ACCESSORS_HASH (destination))
+	{
+	  first_lock = accessors_locks[ACCESSORS_HASH (source)];
+	  second_lock = accessors_locks[ACCESSORS_HASH (destination)];
+	}
+      else
+	{
+	  first_lock = accessors_locks[ACCESSORS_HASH (destination)];
+	  second_lock = accessors_locks[ACCESSORS_HASH (source)];	  
+	}
+
+      objc_mutex_lock (first_lock);
+      objc_mutex_lock (second_lock);
+      memcpy (destination, source, size);
+      objc_mutex_unlock (second_lock);
+      objc_mutex_unlock (first_lock);
+    }
+}
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 165900)
+++ Makefile.in	(working copy)
@@ -163,6 +163,7 @@  OBJC_SOURCE_FILES = \
    NXConstStr.m \
    Object.m \
    Protocol.m \
+   accessors.m \
    linking.m
 
 # C source files to compile
Index: init.c
===================================================================
--- init.c	(revision 165900)
+++ init.c	(working copy)
@@ -35,6 +35,7 @@  see the files COPYING3 and COPYING.RUNTIME respect
 #include "objc-private/protocols.h" /* For __objc_protocols_init(),
 				       __objc_protocols_add_protocol()
 				       __objc_protocols_register_selectors() */
+#include "objc-private/accessors.h" /* For __objc_accessors_init() */
 
 /* The version number of this runtime.  This must match the number 
    defined in gcc (objc-act.c).  */
@@ -582,6 +583,7 @@  __objc_exec_class (Module_t module)
 					   (hash_func_type)objc_hash_ptr,
 					   objc_compare_ptrs);
       __objc_protocols_init ();
+      __objc_accessors_init ();
       __objc_sync_init ();
       previous_constructors = 1;
     }
Index: objc-private/accessors.h
===================================================================
--- objc-private/accessors.h	(revision 0)
+++ objc-private/accessors.h	(revision 0)
@@ -0,0 +1,40 @@ 
+/* GNU Objective C Runtime accessors - Private Declarations
+   Copyright (C) 2010 Free Software Foundation, Inc.
+   Contributed by Nicola Pero <nicola.pero@meta-innovation.com>
+
+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 3, 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.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef __objc_private_accessors_INCLUDE_GNU
+#define __objc_private_accessors_INCLUDE_GNU
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/* This function needs to be called at startup by init.c.  */
+void
+__objc_accessors_init (void);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* not __objc_private_accessors_INCLUDE_GNU */
Index: ChangeLog
===================================================================
--- ChangeLog	(revision 165900)
+++ ChangeLog	(working copy)
@@ -1,3 +1,11 @@ 
+2010-10-24  Nicola Pero  <nicola.pero@meta-innovation.com>
+
+	* Makefile.in (OBJC_SOURCE_FILES): Added accessors.m.
+	* accessors.m: New.
+	* init.c: Include objc-private/accessors.h.
+	(__objc_exec_class): Call __objc_accessors_init.
+	* objc-private/accessors.h: New.
+
 2010-10-17  Nicola Pero  <nicola.pero@meta-innovation.com>
 
 	* objc/message.h: Moved initial includes outside of extern "C".