This is one of those Android design decisions that Google probably wishes they could get to do over again. The DEX header file format allocates only 2 bytes to hold the number of methods the app can reference. This was a very short sighted decision that has come back to bite them repeatedly. It would be interesting to know why they only allocated 2 bytes instead of 4 which would have given them the ability to reference over 4 billion methods. If their reasoning was for cost saving measures than it was a pretty silly decision. There has been some talk about revising the DEX header file format to correct some of the early design mistakes, but I'm not sure when they'll get around to it.
> This is one of those Android design decisions that Google probably wishes they could get to do over again.
Doubtful. This decision is what allowed Android to perform reasonably even in the early days circa 2008. Without such a restriction, it's possible that Android couldn't have competed with iOS on performance and die as a consequence.
It's easy to make fun of technical decisions made ten years ago, try to put things in perspective.
Besides, even today, this 65k limit is barely a minor annoyance that only a very tiny percentage of Android apps ever hit (and there are easy workarounds).
> this 65k limit is barely a minor annoyance that only a very tiny percentage of Android apps ever hit
This is not true, you can easily hit this limit because of a dependency that you _need_ that pulls e.g. Gauva, of when you use 2 or 3 libraries from Play Services, which are huge
> (and there are easy workarounds)
Easy maybe, but the issue is still more than _a minor annoyance_ imo
I've hit the limit when pulling in all Play services. The key is to only pull in what you will be using. Many tutorials(including one from a third party analytics API) are a bit lazy and just have you import Play in its entirety.
>Tor: So [regarding] the infamous 64k method [issue].. I understand that it is a dex file format limitation.. which is a short integer. Do you have plans to address this somehow, by either change the dex format or some other way?
>Anwar: So we've talked about revving DEX, so that limitation doesn't exist anymore. And there's a couple of reasons we haven't done that: one, there're other things we would like to do better as well, including supporting new language features. The other reason is - it doesn't help us with devices still in the field. It's hard to go and say "by the way, we're going to upgrade your runtime.."
So what do we do in order to address that? We will do the DEX byte code [change], but I think there's sort of building block that we needed first - what we're calling multi-DEX. And the idea is.. here's something people were doing - they were breaking up their files into multiple DEX files (each of which exceeds the 64k limit), the main classes in DEX file could see the classes and use them in sort of references rather than loading those classes and having limitations in how you can use them. They will go and use reflection to find the boot class path and modify it to include their secondary DEX files. So this is kind of hack, but a necessary one for them.
>What we're doing in L is in runtime we will have a native support for multi-DEX. All your DEX files that you have in your app will get dexopt-ed or compiled by us and collapsed into a single .oat file which is a binary file we generate.. ..And we have a support library on top of that.. ..if you have multi-DEX it will work on older releases of Android back to Ice Cream Sandwich.. will work on Gingerbread too, but we're only validating back to ICS. So once you have that, than that free's you in the future to do the DEX byte code change, and then something that partitions it and runs on the existing [devices]..
One interesting note is that he mentions that they'll hopefully have the DEX revision by M. Well, we're on N so it looks like they missed that target date. Perhaps O will finally get the long awaited DEX file format revision.
Yeah, why they don't enforce this is baffling. I can give them a break for letting their OEM's take their time with OS updates, but not requiring their OEM's to issue security patches is negligent.
Yeah, it's not like Samsung can go make iOS phones. And I highly doubt any of these hardware OEMs could possibly pull off a software project that doesn't suck, let alone a whole OS and dev ecosystem.
Samsung already releases phones running Tizen to have a side bet against Android. The quality of software is not very important when your only competitor builds phones that are significantly more expensive.
So why can't Google create a new version of the dex format, update Android Studio to generate it, and update the store to accept and distribute it to new devices? Seems easy enough for Google to be able to do.
You make it sound like it is as simple as that, only a method table instead of a header field :)
That said, you mention using a varint or uint32 which "use more CPU or memory" -- 16 bits vs 32 bits in applications that use megabytes seems trivial. Can you explain why that's a concern?
It's not a concern anymore, but when Android was created, the average application was less than 20kiB. Back then, resource restrictions were a lot more problematic.
