Using static immutable Exceptions (or other way for NON-GC exceptions)

[Timo Sintonen via D.gnu]

On Wednesday, 18 February 2015 at 13:07:12 UTC, Iain Buclaw wrote:
> On 18 February 2015 at 12:34, Timo Sintonen via D.gnu
> <d.gnu at puremagic.com> wrote:
>> On Wednesday, 18 February 2015 at 12:12:04 UTC, Iain Buclaw 
>> wrote:
>>
>>>
>>> You can't throw without a GC allocation currently.  I'm open 
>>> to
>>> suggestions and patches welcome.
>>>
>>> See here:
>>> https://github.com/D-Programming-GDC/GDC/blob/master/libphobos/libdruntime/gcc/deh.d#L152
>>>
>>>
>>> Iain.
>>
>>
>> I was just goimg to ask about the state of this.
>> I have understood that this struct carries all the necessary 
>> info trough
>> unwinding and it is not freed until gc frees it.
>> Where is the last place this struct is used. Is it in druntime 
>> side or in
>> libgcc side?
>
> The last place it is used is on the libgcc side, or at least the
> generic exception header that our language-dependent header 
> holds.
>
> It may be a better solution to have a static TLS pointer that 
> gets
> new'd upon thread start.  Perhaps even make it a pre-allocated 
> array
> so we might be able to get chained exceptions working in GDC 
> runtime.
>
>> Could it be possible to allocate this with malloc and free 
>> after unwinding?
>> I have understood that this struct is not available any more 
>> in catch block.
>> Do we need many copies of this. Could it be possible to have a 
>> static one?
>
> See __gdc_exception_cleanup just above _d_throw.  We use 
> destroy(p) in
> the cleanup.  It could work to swap 'destroy' with 'free', and 
> 'new'
> with 'calloc'.  But that still doesn't help if we are throwing 
> an
> OutOfMemory exception.  It will still fail hard, rather than 
> bail with
> a nice backtrace.
>
> Iain

Out Of Memory is a special case and usually a fatal case. There 
was some discussions lately about this but I did not follow it.
If OutOfMemory is not working anyway then we do not loose 
anything? We may get the other exceptions to work. So why not 
make this until we find out some better solution?