macOS Catalina, 64-bit, 32-bit, and related Questions

Re:macOS Catalina, 64-bit, 32-bit, and related Questions by xmichael999 on Saturday June 22, 2019 @07:14PM (#20252240)

Can someone explain to me what Apple gains by dropping 32-bit app support?

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by msbarnett on Saturday June 22, 2019 @08:42PM (#20252567)

32 bit code is stuck with the older ObjC runtime, which can’t support a bunch of new language features and suffers from from fragile ABI issues which make changing the internals of classes extremely problematic.

It’s not simple to fix (“just upgrade the runtime to support the new features”) because the newer runtime trades on the fact that a bunch of unused space in 64 bit pointers can be exploited for tagging, pointerless classes and a bunch of other things. And if they did fix the fragile ivar problem on the 32bit runtime, you’d need to recompile to use the new way of dynamically calculating strict offsets to member fields — and these apps are mostly dying with 32bit precisely because no one is recompiling them.

It’s basically dead-end code that is difficult to maintain and which increasingly requires the rest of the OS to stagnate just to keep it running.

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by mrpippy on Sunday June 23, 2019 @02:12AM (#20253575)

Also: the Carbon API set is only supported on 32-bit, and removing 32-bit means all of Carbon can go away. Carbon is a massive API set, with one or sometimes two full legacy APIs (often dating back to the 90s) for everything. Drawing (QuickDraw), multimedia (QuickTime), open/save dialogs (NavServices), fonts/text rendering (Font Manager, ATSUI), windows/menus/dialogs (both HIToolbox and the classic Managers), file I/O, printing, and on and on. Keeping all this stuff functional (to support old apps) while evolving the system underneath is a huge burden which will be lifted from 10.15 on.

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by xenadu02 on Saturday June 22, 2019 @08:37PM (#20252553)

32-bit macOS uses the older fragile ObjC runtime. Meaning no macOS frameworks present on 32-bit macOS could adopt newer features. In fact they couldn’t even add new ivars because that changes the class layout and would be ABI-breaking.

That’s beside the increased disk space and memory used having two copies of everything.

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by agloeregrets on Saturday June 22, 2019 @11:06PM (#20253050)

Another factor is if they eventually move to their ARM chips in Macs they need to deal with the fact that The Ax CPUs lack 32Bit support and are 64Bit only.

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by scarface74 on Saturday June 22, 2019 @07:17PM (#20252257)

That’s less of a surface area to support, maintain, or to have to worry about security vulnerabilities.

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Re:macOS Catalina, 64-bit, 32-bit, and related Questions by whynotminot on Saturday June 22, 2019 @07:56PM (#20252413)

Security.

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