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Avoid warnings in the Objective-C uniquifying code when running in GC mode.

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51586 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
David Elliott 2008-02-08 04:24:35 +00:00
parent 6a5c31c285
commit 49bd8fd291
1 changed files with 28 additions and 2 deletions
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30
include/wx/cocoa/objc/objc_uniquifying.h
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@ -83,6 +83,32 @@ struct UniquifiedName
}
};
/*! @function HidePointerFromGC
@abstract Returns an l-value whose location the compiler cannot know.
@discussion
The compiler-generated Objective-C class structures are located in the static data area.
They are by design Objective-C objects in their own right which makes the compiler issue
write barriers as if they were located in the GC-managed heap as most Objective-C objects.
By accepting and returning a reference to any pointer type we can set any i-var of an
Objective-C object that is a pointer to another Objective-C object without the compiler
generating an objc_assign_ivar write barrier. It will instad generate an
objc_assign_strongCast write barrier which is the appropriate write-barrier when assigning
pointers to Objective-C objects located in unknown memory.
For instance:
Class *someClass = ...;
HidePointerFromGC(someClass->isa) = ...;
*/
template <typename ObjcType>
inline ObjcType * & HidePointerFromGC(ObjcType * &p) __attribute__((always_inline));
template <typename ObjcType>
inline ObjcType * & HidePointerFromGC(ObjcType * &p)
{
return p;
}
template <typename ObjcType>
class wxObjcClassInitializer
{
@ -131,9 +157,9 @@ private:
// In any object hierarchy a metaclass's metaclass is always the root class's metaclass
// Therefore, our superclass's metaclass's metaclass should already be the root class's metaclass
theClassData.isa->isa = theClassData.super_class->isa->isa;
HidePointerFromGC(theClassData.isa->isa) = theClassData.super_class->isa->isa;
// A metaclass's superclass is always the superclass's metaclass.
theClassData.isa->super_class = theClassData.super_class->isa;
HidePointerFromGC(theClassData.isa->super_class) = theClassData.super_class->isa;
// Fix up the compiler generated metaclass struct to use the new name
theClassData.isa->name = sm_theUniquifiedClassName;