Usually the way you get an NSAtom is because you’re reading garbage–either
somebody scribbled over your pointer or it was garbage to begin with. Does
mCocoaPopupPtr ever get set to nil? Does it have a consistent value? What
happens if you run with the Address Sanitizer enabled, or with NSZombieEnabled
set?
Saagar Jha
> On Sep 7, 2018, at 10:46, Casey McDermott <supp...@turtlesoft.com> wrote:
>
> We need to link some of our C++ classes to a matching Cocoa class.
> It's easy for Cocoa to reference C++ objects. Going the other way is harder.
>
> We have been using a linker class that has a void pointer to the Obj-C object
> in the C++ header. We then cast it to a Cocoa object in the Obj-C++ source.
> For example, in the C++ header we have:
>
> void *mCocoaPopupPtr = nil;
>
> Then in the source:
>
> void GSCocoaPopupLinker::setCocoaFieldVisible(const BOOL inValue)
> {
> if (mCocoaPopupPtr != nil)
> {
> GSPopupButton *cocoaPopup = (__bridge GSPopupButton
> *)mCocoaPopupPtr;
> [cocoaPopup setHidden : !inValue];
> }
> }
>
> Problem is, with ARC turned on, the pointer is never nil, so it crashes.
> The void pointer somehow becomes an NSAtom instead of 0.
>
> There's very little documentation on NSAtom, but it appears to be Apple's way
> to
> use the excess bits in a 64-bit address to store class info.
>
> Is there some other way to test for an invalid void pointer?
>
> Thanks,
>
> Casey McDermott
> TurtleSoft.com
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