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by kuschku
3422 days ago
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It's not that easy, and not just one field. DEX uses a method table, listing every method with an ID, and using in the rest of the file only that ID to refer to it. This ID is limited to 2 bytes. Obviously, thats an issue, but short of using varint or straightaway uint32 there's few alternatives. And those use either more CPU or memory. |
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>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.