[phobos] Typo (bug) in std.concurrency
Andrei Alexandrescu
andrei at erdani.com
Fri Jul 30 23:45:59 PDT 2010
I think it's fair to cast shared away on certain core fns.
Sent by shouting through my showerhead.
On Jun 30, 2010, at 1:37 PM, Sean Kelly <sean at invisibleduck.org> wrote:
> Okay, alternate evil solution:
>
> class Condition
> {
> shared void notify()
> {
> static void doNotify() {}
> (cast(Condition) this).doNotify();
> }
> }
>
> Seems like it should work, though I'm hoping that the classes in
> core.sync are about the only ones where it's necessary (something
> similar will probably be necessary for Mutex to make lock() and
> unlock() explicitly callable, etc). I'm half tempted to try
> labeling these functions as __gshared and see if it compiles.
>
> On Jun 30, 2010, at 1:24 PM, Sean Kelly wrote:
>
>> Well that was a disaster. I have this:
>>
>> class MessageBox
>> {
>> this()
>> {
>> // this makes m_lock the monitor for the MessageBox instance.
>> m_lock = new Mutex( this );
>> m_cond = new Condition( m_lock );
>> }
>>
>> final synchronized void put( Message msg )
>> {
>> // m_lock is locked now
>> m_list.add( msg );
>> m_cond.notify(); // error: notify () is not callable using
>> argument types () shared
>> }
>> }
>>
>> struct Tid
>> {
>> shared MessageBox mbox;
>> }
>>
>> class Condition
>> {
>> void notify()
>> {
>> // fancy stuff involving semaphores
>> }
>> }
>>
>> How do I fix this? Condition.notify() is technically shared, but I
>> don't want to pay the cost for memory barriers that are utterly
>> pointless. Should I change the call to notify() to:
>>
>> (cast(Condition)m_cond).notify();
>>
>> This should work, but it seems like an even worse subversion of the
>> shared system than I'm already doing for MessageBox. If it helps,
>> MessageBox is a thread-local class instance with put() as its one
>> shared public method, so other threads have a shared reference to
>> MessageBox while the object's owner has a non-shared reference to
>> it. This is functionally correct, though it seems theoretically
>> wrong to have both shared and unshared references to the same
>> instance in the first place.
>>
>>
>> On Jun 30, 2010, at 12:27 PM, Sean Kelly wrote:
>>
>>> Looks like it's time I start labeling references as shared in
>>> std.concurrency. The static checking is new.
>>>
>>> On Jun 30, 2010, at 12:15 PM, Lars Tandle Kyllingstad wrote:
>>>
>>>> Great, thanks! I can confirm that receiveTimeout() doesn't hang
>>>> anymore.
>>>>
>>>> I just encountered another problem with the SVN version of
>>>> std.concurrency. The following code is a simplified version of
>>>> an idiom
>>>> which is used in TDPL, namely, sending a Tid as a message:
>>>>
>>>> import std.concurrency;
>>>>
>>>> void main()
>>>> {
>>>> Tid someTid;
>>>> someTid.send(thisTid);
>>>> }
>>>>
>>>> Upon compilation, I get the following error:
>>>>
>>>> /home/lars/code/phobos-trunk/phobos/std/concurrency.d(217): Error:
>>>> static assert "Aliases to mutable thread-local data not allowed."
>>>> a.d(6): instantiated from here: send!(Tid)
>>>>
>>>> I do not get this message when I compile with the released (2.047)
>>>> version of std.concurrency.
>>>>
>>>> -Lars
>>>>
>>>>
>>>> On Wed, 2010-06-30 at 11:36 -0700, Sean Kelly wrote:
>>>>> Okay, should be fixed now.
>>>>>
>>>>> On Jun 30, 2010, at 8:38 AM, Sean Kelly wrote:
>>>>>
>>>>>> Oh well, looks like I have even more fixing to do :-)
>>>>>>
>>>>>> On Jun 30, 2010, at 7:35 AM, Lars Tandle Kyllingstad wrote:
>>>>>>
>>>>>>> Yeah, I noticed that you committed the fix, but too late. :)
>>>>>>> Due to
>>>>>>> some server lag, I got the "phobos commit" message several
>>>>>>> hours after I
>>>>>>> sent my e-mail, even though the commit was apparently done
>>>>>>> before I sent
>>>>>>> it.
>>>>>>>
>>>>>>> In case it's useful, I should mention that even after fixing
>>>>>>> the tuple
>>>>>>> issue and changing the return type of receiveTimeout() to
>>>>>>> void, it still
>>>>>>> doesn't work. The following code hangs indefinitely:
>>>>>>>
>>>>>>> import std.concurrency;
>>>>>>>
>>>>>>> void main()
>>>>>>> {
>>>>>>> // Should only block for 1ms:
>>>>>>> receiveTimeout(1, (int i) { });
>>>>>>> }
>>>>>>>
>>>>>>> -Lars
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, 2010-06-29 at 20:47 -0700, Sean Kelly wrote:
>>>>>>>> The code has changed a ton recently and I hadn't gotten
>>>>>>>> around to testing receiveTimeout yet. I'll take care of it.
>>>>>>>>
>>>>>>>> Sent from my iPhone
>>>>>>>>
>>>>>>>> On Jun 29, 2010, at 4:09 PM, Lars Tandle Kyllingstad <lars at kyllingen.net
>>>>>>>> > wrote:
>>>>>>>>
>>>>>>>>> I'm guessing this error turned up because someone tried to use
>>>>>>>>> receiveTimeout(). That's when it happened for me, at
>>>>>>>>> least. But when I
>>>>>>>>> fixed this, another error occurred:
>>>>>>>>>
>>>>>>>>> receiveTimeout() is supposed to return a bool, but it tries
>>>>>>>>> to return
>>>>>>>>> the result of MessageBox.get(), which is void. So get()
>>>>>>>>> should, in the
>>>>>>>>> case when ops[0] is an integer, somehow detect whether a
>>>>>>>>> message was
>>>>>>>>> received within the time limit and return a bool.
>>>>>>>>>
>>>>>>>>> Sean, if you aren't working on this already, I can look into
>>>>>>>>> it if you
>>>>>>>>> like.
>>>>>>>>>
>>>>>>>>> -Lars
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Tue, 2010-06-29 at 09:40 -0700, Sean Kelly wrote:
>>>>>>>>>> Okay I guess that makes sense. Should be easy enough to
>>>>>>>>>> fix anyway.
>>>>>>>>>>
>>>>>>>>>> On Jun 29, 2010, at 8:43 AM, Steve Schveighoffer wrote:
>>>>>>>>>>
>>>>>>>>>>> You can't slice a tuple and assign it back to the same
>>>>>>>>>>> tuple type.
>>>>>>>>>>>
>>>>>>>>>>> -Steve
>>>>>>>>>>>
>>>>>>>>>>> ----- Original Message ----
>>>>>>>>>>>> From: Sean Kelly <sean at invisibleduck.org>
>>>>>>>>>>>> To: Discuss the phobos library for D <phobos at puremagic.com>
>>>>>>>>>>>> Sent: Tue, June 29, 2010 11:39:50 AM
>>>>>>>>>>>> Subject: Re: [phobos] Typo (bug) in std.concurrency
>>>>>>>>>>>>
>>>>>>>>>>>> On Jun 29, 2010, at 7:00 AM, Simen Kjaeraas wrote:
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> http://d.puremagic.com/issues/show_bug.cgi?id=4406
>>>>>>>>>>>>
>>>>>>>>>>>> Posting it
>>>>>>>>>>>> here too, to make sure it gets noticed. It's a rather
>>>>>>>>>>>> simple fix.
>>>>>>>>>>>
>>>>>>>>>>> You
>>>>>>>>>>>> can't slice a tuple? Seriously? I could have sworn that
>>>>>>>>>>>> I tested
>>>>>>>>>>>> this and it worked.
>>>>>>>
>>>>>>>
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>>>>>>
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