290 lines
9.2 KiB
Objective-C
290 lines
9.2 KiB
Objective-C
/* GNU Objective C Runtime accessors functions
|
|
Copyright (C) 2010-2022 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)
|
|
{
|
|
/* Note that in this case, we do not RETAIN/AUTORELEASE the
|
|
returned value. The programmer should do it if it is
|
|
needed. Since access is non-atomic, other threads can be
|
|
ignored and the caller has full control of what happens
|
|
to the object and whether it needs to be RETAINed or not,
|
|
so it makes sense to leave the decision to him/her. This
|
|
is also what the Apple/NeXT runtime does. */
|
|
return *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);
|
|
}
|
|
}
|