Are you compiling with c++14 features enabled? Usually the `-std=c++1y`
flag will do that.
- David
On Tue, May 31, 2016 at 11:27 AM, Abhishek Balaji Radhakrishnan <
abhishek.r...@gmail.com> wrote:
> Hi David and Kenton,
>
> I have a similar usecase for a project and I am trying to replicate this
> example to see how it works, but the server code in this case is throwing
> errors. Not sure what might have changed over time.
>
> A gist of the error is as follows:
> entry_ss.c++: In member function ‘void
> EntryPusher::pushEntryInternal(int)’:
> entry_ss.c++:29:53: error: parameter declared ‘auto’
> taskSet.add(entryReq.send().then([this, i](auto x) {
> ^
> entry_ss.c++: In lambda function:
> entry_ss.c++:34:69: error: parameter declared ‘auto’
> taskSet.add(processor.doneRequest().send().then([](auto x)
> {}));
> ^
> In file included from /usr/local/include/kj/async.h:29:0,
> from /usr/local/include/capnp/capability.h:33,
> from /usr/local/include/capnp/rpc.h:29,
> from /usr/local/include/capnp/ez-rpc.h:29,
> from entry_ss.c++:5:
>
> ...
>
>
> I see that the pushEntryInternal() is causing the problem with the then()
> semantics - not sure how to fix this:
>
> void pushEntryInternal(int i) {
> auto entryReq = processor.processRequest();
> entryReq.getEntry().setData(i);
> taskSet.add(entryReq.send().then([this, i](auto x) {
> usleep(500000);
> if (i > 0) {
> pushEntryInternal(i - 1);
> } else {
> taskSet.add(processor.doneRequest().send().then([](auto x)
> {}));
> }
> }));
> }
>
>
> Thanks,
> Abhishek
>
>
>
> On Tuesday, 21 October 2014 21:47:21 UTC-4, David Renshaw wrote:
>>
>> Ouch. Looks like `GC_apply_to_all_blocks()` doesn't give you any chance
>> to yield control. So though you can queue up as many sends as you like,
>> they won't get executed until `GC_apply_to_all_blocks()` completes. You'd
>> be better off just buffering the GCEntries in a list.
>>
>> If you don't want to buffer all of the GCEntry objects in memory before
>> sending them, then I think you're forced to put the call to
>> `GC_apply_to_all_blocks()` in a separate thread. You could communicate with
>> that thread using a socketpair, receiving the GCEntries back as a raw
>> stream of Cap'n Proto messages, and then forwarding the entries to the
>> `sendGCEntry()` method. The read methods declared in serialize-async.h
>> allow you to do this in a way that plays nicely with the event loop.
>>
>>
>> -David
>>
>>
>> On Tue, Oct 21, 2014 at 6:51 PM, Turing Eret <er...@lambdacalcul.us>
>> wrote:
>>
>>> Easier to do in theory than practice. In my actual program, my
>>> equivalent of pushEntry() is this:
>>>
>>> void processMonoObjects(mono_object_processor f, void* user_data)
>>>
>>> {
>>>
>>> mono_gc_disable();
>>>
>>>
>>>
>>> MonoHeapProcessorState state;
>>>
>>>
>>>
>>> state.vtables = getAllVTables();
>>>
>>> state.processor = f;
>>>
>>> state.user_data = user_data;
>>>
>>>
>>>
>>> GC_apply_to_all_blocks(blockProcessor, (word)&state);
>>>
>>>
>>>
>>> mono_gc_enable();
>>>
>>> }
>>>
>>> where mono_object_processor is defined as this:
>>>
>>> typedef void (__cdecl *mono_object_processor)(MonoObject* obj, void*
>>> user_data);
>>>
>>>
>>> Now, my equivalent of pushEntryInternal() is one of those
>>> mono_object_processor functions and GC_apply_to_all_blocks() calls that
>>> function on all the blocks known by the GC. Unfortunately, that isn't
>>> something I wrote nor something I can change. I attempted this:
>>>
>>> void scrapHeapProcessor(MonoObject* obj, HeapScraper* heapScraperPtr)
>>>
>>> {
>>>
>>> heapScraperPtr->promise = heapScraperPtr->promise.then([=]()
>>>
>>> {
>>>
>>>
>>> heapScraperPtr->sendGCEntry(obj);
>>>
>>> });
>>>
>>> }
>>>
>>>
>>> void HeapScraper::startScraping()
>>>
>>> {
>>>
>>> processMonoObjects((mono_object_processor)scrapHeapProcessor, this);
>>>
>>> taskSet.add(std::move(promise));
>>>
>>> }
>>>
>>>
>>> Unfortunately, this exploded badly in a stack overflow. Is that what you
>>> were suggesting? Is there a better way to do this that doesn't explode in
>>> my face?
>>>
>>>
>>> Turing
>>>
>>> On Tuesday, 21 October 2014 15:57:02 UTC-6, David Renshaw wrote:
>>>
>>>>
>>>> On Tue, Oct 21, 2014 at 3:59 PM, Turing Eret <er...@lambdacalcul.us>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> So, each top-level call of pushEntryInternal() descends through to its
>>>>> base case before going up to the next top-level call of
>>>>> pushEntryInternal(), a depth-first traversal of the tasks. Is there any
>>>>> way
>>>>> to do that easily?
>>>>>
>>>>
>>>>
>>>> To accomplish that, I would redefine `pushEntryInternal()` so that it
>>>> returns a `kj::Promise<void>`, to be fulfilled when all the entries have
>>>> been pushed. Then I would chain the calls to `pushEntryInternal()` using
>>>> the `then()` method.
>>>>
>>>>
>>>>> PS: On a completely unrelated note, is there a document somewhere
>>>>> showing what languages have plugins currently in development and who is
>>>>> working on the plugin?
>>>>>
>>>>
>>>> Yes: https://kentonv.github.io/capnproto/otherlang.html
>>>>
>>>>
>>>> -David
>>>>
>>>>
>>
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