Change the name of ArrayBoundsException in druntime

[Andrei Alexandrescu]

Sean Kelly wrote:
> Denis Koroskin wrote:
>>
>> I think that OutOfMemoryException should *not* be recoverable. 
>> Instead, language should provide some hookable callback (like 
>> onOutOfMemoryError()) which is called when memory limit is reached so 
>> that program may free some unused memory (which is held by user since 
>> it is not garbage-collected) and tries to allocate the memory again 
>> without failure (return true from callback). User might decide to 
>> re-throw some other kind of *exception*, like 
>> NotEnoughMemoryException(), to catch and recover, or pass it (return 
>> false from callback) which in turn will finally throw OutOfMemoryError().
> 
> This is a fair point, but how does one implement this safely?  Let's say 
> for the sake of argument that onOutOfMemoryError() can be hooked by the 
> user and may try to recover.  Now:
> 
>     auto x = new int[BIG_NUMBER];
> 
> Let's say that gc_malloc() is implemented like so:
> 
>     void* gc_malloc( size_t sz )
>     {
>         void* ptr;
>         do
>         {
>             ptr = doMalloc(sz);
>             if( ptr is null )
>                 onOutOfMemoryError();
>         } while( ptr is null );
>         return ptr;
>     }
> 
> Now let's assume that the first attempted allocation fails and 
> onOutOfMemoryError() frees some memory rather than throwing so the 
> allocation is attempted again.  But BIG_NUMBER is so darn big that the 
> allocation fails again.  And once again onOutOfMemoryError() tries to 
> free some memory and returns instead of throwing.  Is there any way to 
> structure the recovery mechanism to avoid this situation given that 
> onOutOfMemoryError() has no idea that it's being called in such a loop? 
>  gc_malloc() could certainly give up and throw after a certain number of 
> failed attempts, but putting the onus on the caller of 
> onOutOfMemoryError() to deal with this situation is not reasonable in my 
> opinion.

Perfectly put. Again: why prevent use of exceptions for the one case 
that they fit the best?


Andrei