[Mono-dev] AOT and generics

[Rodrigo Kumpera]

The FullAOT compiler handles generics by compiling a single shared instance
for all ref-only type arguments.
so List<object> shares code with List<string> but List<int> gets its own
version. This is the default behavior.

If this is not the case, then you have something broken in your setup.


On Fri, Jul 6, 2012 at 11:24 AM, Virgile Bello <virgile.bello at gmail.com>wrote:

> It would be for platforms supporting only AOT.
> Of course we would license Mono. We already had a quick discussion about
> licensing maybe a year ago (it's still R&D/proof of concept for now, and it
> was only Windows until now so we just delayed actual deal until necessary),
> but thanks for pointing out, maybe now is a good time to start the
> discussion again with Xamarin, I will send an email right away.
>
>
> On Fri, Jul 6, 2012 at 10:31 PM, Rodrigo Kumpera <kumpera at gmail.com>wrote:
>
>> You need to correctly drive the FullAOT compiler.
>> Why do you want to use FullAOT anyway?
>> Do you plan to run it on a target that disables JIT?
>> Do you hold a license that allows you to do so? Mono is LGPL and FullAOT
>> doesn't work with it.
>>
>> On Fri, Jul 6, 2012 at 9:29 AM, Virgile Bello <virgile.bello at gmail.com>wrote:
>>
>>> During full AOT, It seems that if generics is a ref type, AOT is skipped
>>> (which makes sense because most of the time it is not necessary, one
>>> codegen for any ref type is usually enough).
>>> However, if the class internally uses a struct based on the generic
>>> types, it will fail at runtime.
>>> Here is a simple example showcasing the issue:
>>>
>>> public class B
>>> {
>>>     public void Test<T>()
>>>     {
>>>         System.Console.WriteLine(typeof(T));
>>>     }
>>> }
>>>
>>> public class A<T>
>>> {
>>>     public void Test()
>>>     {
>>>         new B().Test<System.Collections.Generic.KeyValuePair<T, T>>();
>>>     }
>>> }
>>>
>>>
>>> class P
>>> {
>>>     static void Main(string[] args)
>>>     {
>>>         new A<int>().Test();
>>>         new A<string>().Test();
>>>     }
>>> }
>>>
>>> If I run this program with full aot, it will fail.
>>> new A<int> will work (AOT forced because value type)
>>> However, new A<string> will generate a JIT exception (because even
>>> though string is a ref type, A should be AOT for this specific type because
>>> KeyValuePair inside A<T> needs to be JITed.)
>>>
>>> But maybe I misunderstood the problem (or it is just a specific bug),
>>> because this other case actually work (I was expecting it to have the same
>>> issue):
>>>
>>> public class B
>>> {
>>>     public void Test<T>()
>>>     {
>>>
>>> System.Console.WriteLine(typeof(System.Collections.Generic.KeyValuePair<T,
>>> T>));
>>>     }
>>> }
>>>
>>> public class A<T>
>>> {
>>>     public void Test()
>>>     {
>>>         new B().Test<T>();
>>>     }
>>> }
>>>
>>>
>>> class P
>>> {
>>>     static void Main(string[] args)
>>>     {
>>>         new A<int>().Test();
>>>         new A<string>().Test();
>>>     }
>>> }
>>>
>>> Just wanted to check if I understood the issue right and if there would
>>> be nothing preventing from fixing it?
>>> I wouldn't mind taking a look at the sources by myself if necessary.
>>>
>>> Virgile
>>>
>>>
>>> _______________________________________________
>>> Mono-devel-list mailing list
>>> Mono-devel-list at lists.ximian.com
>>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>>
>>>
>>
>
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