How to use @ReservedStackAccess?

[Nicolai Parlog]

 Hi David,

oh, now I get it! I knew that I only get 4k of reserved space but I
didn't quite get where computation would resume once stack space ran
out. I got lost in the weeds and thought the JVM would fall back to
the annotated frame and somehow continue in there... But it's much
simpler: I just get a little more rope to hang myself with. :)

 Thanks!
 Nicolai



On 01.11.2016 02:45, David Holmes wrote:
> Hi Nicolai,
> 
> On 1/11/2016 1:39 AM, Nicolai Parlog wrote:
>> Hi!
>> 
>> I've been experimenting with @ReservedStackAccess but couldn't
>> get it to work. Any help would be highly appreciated.
>> 
>> ## SETUP
>> 
>> I'm artificially creating a stack overflow by recursing
>> indefinitely. I then want to benefit from @ReservedStackAccess by
>> executing some code outside of an exception handler.
>> 
>> Here's my code:
>> 
>> public static void main(String[] args) { try { 
>> recurseThenGreet(); } catch (StackOverflowError err) { // to not
>> have the console spammed with output 
>> System.out.println("Error"); } }
>> 
>> @ReservedStackAccess private static void recurseThenGreet() { 
>> recurse(); System.out.println("Hi!"); }
>> 
>> private static void recurse() { recurse(); }
>> 
>> I'm using build 9-ea+141-jigsaw-nightly-h5650-20161026. I compile
>> with
>> 
>> --add-exports java.base/jdk.internal.vm.annotation=ALL-UNNAMED
>> 
>> to make the annotation available and launch with
>> 
>> -XX:-RestrictReservedStack
>> 
>> to activate the reserved stack for user land code.
>> 
>> ## OBSERVED
>> 
>> This is the output I get:
>> 
>> Java HotSpot(TM) 64-Bit Server VM warning: Potentially dangerous
>> stack overflow in ReservedStackAccess annotated method 
>> org.codefx.demo.java9.internal.stack.ReservingStackFrames_Simple.recu
rseThenGreet()V[1]
>>
>>
>> 
Error
>> 
>> ## EXPECTED
>> 
>> I expected "Hi!" to show up somewhere there.
> 
> ReservedStackAccess doesn't give you unlimited stack, it gives you
> a little extra to try and complete the method that was annotated.
> In your case you will continue to recurse and exhaust the
> additional stack area as well.
> 
> David -----
> 
>> My best guess is that I put the annotation in the wrong place
>> but experimenting didn't help. Any help would be greatly
>> appreciated!
>> 
>> Thanks! Nicolai
>> 
>> 
>> 
> 

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