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253 lines
7.4 KiB
C
253 lines
7.4 KiB
C
#include <assert.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include "objc/runtime.h"
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#include "objc/objc-arc.h"
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#include "class.h"
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#include "ivar.h"
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#include "visibility.h"
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#include "gc_ops.h"
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ptrdiff_t objc_alignof_type(const char *);
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ptrdiff_t objc_sizeof_type(const char *);
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PRIVATE void objc_compute_ivar_offsets(Class class)
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{
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int i = 0;
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/* If this class was compiled with support for late-bound ivars, the
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* instance_size field will contain 0 - {the size of the instance variables
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* declared for just this class}. The individual instance variable offset
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* fields will then be the offsets from the start of the class, and so must
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* have the size of the parent class prepended. */
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if (class->instance_size <= 0)
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{
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Class super = class_getSuperclass(class);
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long ivar_start = 0;
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if (Nil != super)
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{
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if (super->instance_size <= 0)
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{
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objc_compute_ivar_offsets(super);
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}
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ivar_start = super->instance_size;
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}
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long class_size = 0 - class->instance_size;
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class->instance_size = ivar_start - class->instance_size;
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/* For each instance variable, we add the offset if required (it will be zero
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* if this class is compiled with a static ivar layout). We then set the
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* value of a global variable to the offset value.
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*
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* Any class compiled with support for the non-fragile ABI, but not actually
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* using it, will export the ivar offset field as a symbol.
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*
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* Note that using non-fragile ivars breaks @defs(). If you need equivalent
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* functionality, provide an alternative @interface with all variables
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* declared @public.
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*/
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if (class->ivars)
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{
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for (i = 0 ; i < class->ivars->count ; i++)
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{
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struct objc_ivar *ivar = &class->ivars->ivar_list[i];
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// We are going to be allocating an extra word for the reference count
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// in front of the object. This doesn't matter for aligment most of
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// the time, but if we have an instance variable that is a vector type
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// then we will need to ensure that we are properly aligned again.
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long ivar_size = (i+1 == class->ivars->count)
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? (class_size - ivar->offset)
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: ivar->offset - class->ivars->ivar_list[i+1].offset;
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// We only need to do the realignment for things that are
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// bigger than a pointer, and we don't need to do it in GC mode
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// where we don't add any extra padding.
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if (!isGCEnabled && (ivar_size > sizeof(void*)))
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{
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long offset = ivar_start + ivar->offset + sizeof(intptr_t);
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// For now, assume that nothing needs to be more than 16-byte aligned.
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// This is not correct for AVX vectors, but we probably
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// can't do anything about that for now (as malloc is only
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// giving us 16-byte aligned memory)
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long fudge = 16 - (offset % 16);
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if (fudge != 0)
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{
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ivar->offset += fudge;
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class->instance_size += fudge;
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assert((ivar_start + ivar->offset + sizeof(intptr_t)) % 16 == 0);
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}
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}
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ivar->offset += ivar_start;
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/* If we're using the new ABI then we also set up the faster ivar
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* offset variables.
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*/
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if (objc_test_class_flag(class, objc_class_flag_new_abi))
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{
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*(class->ivar_offsets[i]) = ivar->offset;
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}
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}
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}
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}
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else
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{
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if (NULL == class->ivars) { return; }
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Class super = class_getSuperclass(class);
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int start = class->ivars->ivar_list[0].offset;
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/* Quick and dirty test. If the first ivar comes straight after the last
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* class, then it's fine. */
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if (Nil == super || start == super->instance_size) {return; }
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/* Find the last superclass with at least one ivar. */
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while (NULL == super->ivars)
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{
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super = class_getSuperclass(super);
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}
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struct objc_ivar *ivar =
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&super->ivars->ivar_list[super->ivars->count-1];
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// Find the end of the last ivar - instance_size contains some padding
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// for alignment.
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int real_end = ivar->offset + objc_sizeof_type(ivar->type);
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// Keep going if the new class starts at the end of the superclass
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if (start == real_end)
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{
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return;
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}
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// The classes don't line up, but don't panic; check that the
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// difference is not just padding for alignment
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int align = objc_alignof_type(class->ivars->ivar_list[0].type);
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if (start > real_end && (start - align) < real_end)
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{
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return;
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}
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/* Panic if this class has an instance variable that overlaps the
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* superclass. */
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fprintf(stderr,
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"Error: Instance variables in %s overlap superclass %s. ",
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class->name, super->name);
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fprintf(stderr,
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"Offset of first instance variable, %s, is %d. ",
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class->ivars->ivar_list[0].name, start);
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fprintf(stderr,
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"Last instance variable in superclass, %s, ends at offset %d. ",
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ivar->name, ivar->offset +
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(int)objc_sizeof_type(ivar->type));
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fprintf(stderr, "This probably means that you are subclassing a"
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"class from a library, which has changed in a binary-incompatible"
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"way.\n");
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abort();
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}
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}
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typedef enum {
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ownership_invalid,
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ownership_strong,
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ownership_weak,
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ownership_unsafe
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} ownership;
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ownership ownershipForIvar(Class cls, Ivar ivar)
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{
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struct objc_ivar_list *list = cls->ivars;
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if ((list == NULL) || (ivar < list->ivar_list)
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|| (ivar >= &list->ivar_list[list->count]))
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{
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// Try the superclass
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if (cls->super_class)
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{
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return ownershipForIvar(cls->super_class, ivar);
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}
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return ownership_invalid;
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}
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if (!objc_test_class_flag(cls, objc_class_flag_new_abi))
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{
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return ownership_unsafe;
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}
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if (cls->abi_version < 1)
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{
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return ownership_unsafe;
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}
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if (objc_bitfield_test(cls->strong_pointers, (ivar - list->ivar_list)))
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{
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return ownership_strong;
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}
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if (objc_bitfield_test(cls->weak_pointers, (ivar - list->ivar_list)))
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{
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return ownership_weak;
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}
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return ownership_unsafe;
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}
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////////////////////////////////////////////////////////////////////////////////
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// Public API functions
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////////////////////////////////////////////////////////////////////////////////
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void object_setIvar(id object, Ivar ivar, id value)
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{
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ownershipForIvar(object_getClass(object), ivar);
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id *addr = (id*)((char*)object + ivar_getOffset(ivar));
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switch (ownershipForIvar(object_getClass(object), ivar))
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{
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case ownership_strong:
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objc_storeStrong(addr, value);
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break;
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case ownership_weak:
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objc_storeWeak(addr, value);
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break;
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case ownership_unsafe:
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*addr = value;
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break;
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case ownership_invalid:
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#ifndef NDEBUG
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fprintf(stderr, "Ivar does not belong to this class!\n");
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#endif
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break;
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}
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}
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Ivar object_setInstanceVariable(id obj, const char *name, void *value)
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{
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Ivar ivar = class_getInstanceVariable(object_getClass(obj), name);
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if (ivar_getTypeEncoding(ivar)[0] == '@')
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{
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object_setIvar(obj, ivar, *(id*)value);
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}
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else
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{
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size_t size = objc_sizeof_type(ivar_getTypeEncoding(ivar));
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memcpy((char*)obj + ivar_getOffset(ivar), value, size);
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}
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return ivar;
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}
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id object_getIvar(id object, Ivar ivar)
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{
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ownershipForIvar(object_getClass(object), ivar);
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id *addr = (id*)((char*)object + ivar_getOffset(ivar));
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switch (ownershipForIvar(object_getClass(object), ivar))
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{
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case ownership_strong:
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return objc_retainAutoreleaseReturnValue(*addr);
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case ownership_weak:
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return objc_loadWeak(addr);
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break;
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case ownership_unsafe:
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return *addr;
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case ownership_invalid:
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#ifndef NDEBUG
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fprintf(stderr, "Ivar does not belong to this class!\n");
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#endif
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return nil;
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}
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}
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Ivar object_getInstanceVariable(id obj, const char *name, void **outValue)
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{
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Ivar ivar = class_getInstanceVariable(object_getClass(obj), name);
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if (NULL != outValue)
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{
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*outValue = (((char*)obj) + ivar_getOffset(ivar));
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}
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return ivar;
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}
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