MAINT-5976: Fix bug in LLCoros::set_consuming() mechanism.

The original implementation of set_consuming() involved a bool* pointing to a
local bool in VoidListener::operator()()'s stack frame. postAndSuspend() would
set that bool (through the pointer) as soon as it returned from suspension.

The trouble with that is that LLEventMailDrop potentially calls its new
listener (fulfilling the future) immediately in the listen_impl() override --
in other words, way up at the top of postAndSuspend(), well before the code
that sets the relevant bool.

Instead, make the adapter formerly known as VoidListener bind the coroutine's
get_consuming() value at adapter construction time (before listening on the
LLEventPump), so that its operator()() has the coroutine's correct
get_consuming() value to return. Eliminating the bool* makes the code both
simpler AND more correct!

This change makes that adapter very specific to coroutine usage. Rename it
FutureListener and migrate it from lleventcoros.h into the .cpp file. Nobody
else was using it anyway.

Make corresponding changes to postAndSuspend2() and its WaitForEventOnHelper
class -- whose name no longer corresponds to the function as it used to.
Rename that one FutureListener2. The new FutureListener functionality, common
to both these adapters, makes it useful to derive FutureListener2 from
FutureListener.

Introduce llmake(), a generic function to deduce template type arguments from
function parameter types. This allows us to remove the voidlistener() and
wfeoh() helper functions.

Hiding VoidListener broke one of the lleventcoro_test.cpp tests. But that test
was sort of a lame recap of an earlier implementation of postAndSuspend(),
based on LLEventPump events. Recast that test to illustrate how to use a
coroutine future to suspend a coroutine for something other than an LLEventPump.

But that rubbed my nose in the fact that we MUST wrap future's context
switching with proper management of the current coroutine. Introduce
LLCoros::Future<T>, which wraps boost::dcoroutines::future<T>.

Use LLCoros::Future<T> in postAndSuspend() and postAndSuspend2().

1 files changed, 0 insertions, 30 deletions

diff --git a/indra/llcommon/lleventcoro.h b/indra/llcommon/lleventcoro.h
index acf2ad24a4..2105faf861 100755
--- a/indra/llcommon/lleventcoro.h
+++ b/indra/llcommon/lleventcoro.h
@@ -76,36 +76,6 @@ private:
 namespace llcoro
 {
 
-typedef std::pair<LLSD, bool*> LLSD_consumed;
-
-/// This is an adapter for a signature like void LISTENER(const LLSD&), which
-/// isn't a valid LLEventPump listener: such listeners should return bool.
-template <typename LISTENER>
-class VoidListener
-{
-public:
-    VoidListener(const LISTENER& listener):
-        mListener(listener)
-    {}
-
-    bool operator()(const LLSD& event)
-    {
-        bool consumed = false;
-        mListener(LLSD_consumed(event, &consumed));
-        // tell upstream LLEventPump whether listener consumed
-        return consumed;
-    }
-private:
-    LISTENER mListener;
-};
-
-/// VoidListener helper function to infer the type of the LISTENER
-template <typename LISTENER>
-VoidListener<LISTENER> voidlistener(const LISTENER& listener)
-{
-    return VoidListener<LISTENER>(listener);
-}
-
 /**
  * Yield control from a coroutine for one "mainloop" tick. If your coroutine
  * runs without suspending for nontrivial time, sprinkle in calls to this