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64-bit and iOS 8 Requirements for New Apps

developer.apple.com

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Re: 64-bit and iOS 8 Requirements for New Apps

#11

Post by melling »

wvenable wrote: post #7
reverend_gonzo wrote: post #5

Earlier quoted context omitted.

Did you read the link? New apps must include 64-bit support. That's it. It says nothing about not allow backwards compatibility as well.

I read the link, I was focusing on the "built with the iOS 8 SDK" part. I'm asking the question whether or not building with the iOS 8 SDK would preclude that code from running on iOS 7 or is that only if that code uses iOS 8 features. I'm not sure why this is news otherwise.

It's not worth being #5 on HN. You can target older versions of iOS.

Re: 64-bit and iOS 8 Requirements for New Apps

#12

Post by paxswill »

joesmo wrote: post #8
reverend_gonzo wrote: post #5

Earlier quoted context omitted.

Did you read the link? New apps must include 64-bit support. That's it. It says nothing about not allow backwards compatibility as well.

They must be built with the iOS 8 SDK so unless that runs on previous versions of iOS, then new apps for previous iOS versions will not be supported.

You can build against a higher SDK version than your minimum requirement with OS X/iOS. For example, your deployment target is OS X 10.7, but yo're building with the OS X 10.10 SDK.

More info: https://developer.apple.com/library/ios/documentation/Develo...

Re: 64-bit and iOS 8 Requirements for New Apps

#13

Post by wvenable »

Osmium wrote: post #10
wvenable wrote: post #7

Earlier quoted context omitted.

I read the link, I was focusing on the "built with the iOS 8 SDK" part. I'm asking the question whether or not building with the iOS 8 SDK would preclude that code from running on iOS 7 or is that only if that code uses iOS 8 features. I'm not sure why this is news otherwise.

> I'm not sure why this is news otherwise. One reason is that, I believe, currently if even a single 32-bit app is loaded on a newer iOS device, all the standard 32-bit libraries have to be loaded into memory as well which causes increased memory pressure. This is a problem given that current iOS devices only have 1 GB of RAM. Getting older apps migrated to 64-bit is therefore a big deal for this reason alone.

I think HN has trained me to be very pessimistic about technology news. When I see a link posted like this without much commentary voted to the front page my first reaction is that it must be bad news.

Re: 64-bit and iOS 8 Requirements for New Apps

#14

Post by dozy »

wvenable wrote: post #7
reverend_gonzo wrote: post #5

Earlier quoted context omitted.

Did you read the link? New apps must include 64-bit support. That's it. It says nothing about not allow backwards compatibility as well.

I read the link, I was focusing on the "built with the iOS 8 SDK" part. I'm asking the question whether or not building with the iOS 8 SDK would preclude that code from running on iOS 7 or is that only if that code uses iOS 8 features. I'm not sure why this is news otherwise.

This is important news for iOS developers as it means they must build and test their app on iOS 8, including any libraries that they use.

There are many ways and reasons why changing your build target may affect your app, so much so that's it's far beyond the scope of a hackernews thread. Supporting 64-bit, although introduced a while ago already with with iPhone 5S, can present some tricky bugs, also too much to explain here.

It's also meta-interesting as it shows the pace at which Apple wants app developers to adopt the new APIs, and will ultimately result in a more modern/ios 8 friendly app landscape.

EDIT: somebody else noted that you can likely still target earlier versions, which on the whole makes this much less interesting.

Re: 64-bit and iOS 8 Requirements for New Apps

#16

Post by marvy »

Osmium wrote: post #10
wvenable wrote: post #7

Earlier quoted context omitted.

I read the link, I was focusing on the "built with the iOS 8 SDK" part. I'm asking the question whether or not building with the iOS 8 SDK would preclude that code from running on iOS 7 or is that only if that code uses iOS 8 features. I'm not sure why this is news otherwise.

> I'm not sure why this is news otherwise. One reason is that, I believe, currently if even a single 32-bit app is loaded on a newer iOS device, all the standard 32-bit libraries have to be loaded into memory as well which causes increased memory pressure. This is a problem given that current iOS devices only have 1 GB of RAM. Getting older apps migrated to 64-bit is therefore a big deal for this reason alone.

If they only have a gig of RAM, why does iOS bother with 64-bit support at all? Doesn't that increase memory pressure due to all the pointers being twice as big?

Re: 64-bit and iOS 8 Requirements for New Apps

#17

Post by Osmium »

marvy wrote: post #16
Osmium wrote: post #10

Earlier quoted context omitted.

> I'm not sure why this is news otherwise. One reason is that, I believe, currently if even a single 32-bit app is loaded on a newer iOS device, all the standard 32-bit libraries have to be loaded into memory as well which causes increased memory pressure. This is a problem given that current iOS devices only have 1 GB of RAM. Getting older apps migrated to 64-bit is therefore a big deal for this reason alone.

If they only have a gig of RAM, why does iOS bother with 64-bit support at all? Doesn't that increase memory pressure due to all the pointers being twice as big?

It's a bit more complicated than that. There's a really good discussion here:

http://www.sealiesoftware.com/blog/archive/2013/09/24/objc_e...

and here:

https://www.mikeash.com/pyblog/friday-qa-2013-09-27-arm64-an...

Basically, as I understand it, 64-bit pointers on iOS can actually act to decrease memory pressure because the extra bits can be used to store object class information that would otherwise have to be stored separately.

Re: 64-bit and iOS 8 Requirements for New Apps

#18

Post by jibberia »

Ah, it finally happened. My company has a legacy-ish SDK that all our products are built on, and because of bad decisions in the past (like extensive use of C macros) it essentially cannot be ported to 64-bit. Luckily we're already building the replacement, but this is going to accelerate the requirement of having to migrate data from the old system to the new one.

Re: 64-bit and iOS 8 Requirements for New Apps

#19

Post by fineline »

jibberia wrote: post #18

Ah, it finally happened. My company has a legacy-ish SDK that all our products are built on, and because of bad decisions in the past (like extensive use of C macros) it essentially cannot be ported to 64-bit. Luckily we're already building the replacement, but this is going to accelerate the requirement of having to migrate data from the old system to the new one.

Is there some problem with macros in the new SDK? Or is it that your macros are specific about word size?

Re: 64-bit and iOS 8 Requirements for New Apps

#20

Post by mackey »

jibberia wrote: post #18

Ah, it finally happened. My company has a legacy-ish SDK that all our products are built on, and because of bad decisions in the past (like extensive use of C macros) it essentially cannot be ported to 64-bit. Luckily we're already building the replacement, but this is going to accelerate the requirement of having to migrate data from the old system to the new one.

At least it sounds like this only applies to new apps, not apps updates for apps that are already published. It would be great to get clarification on that though.
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