From f2f0fa7fd0efc221f1358dd4e440b5d51a5fb8b4 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Thu, 18 Jul 2024 13:29:34 -0400
Subject: Ditch `LLEventTrackable` aka `boost::signals2::trackable`.
Remove documented `LLEventPump` support for `LLEventTrackable`. That claimed
support was always a little bit magical/fragile. IF:
* a class included `LLEventTrackable` as a base class AND
* an instance of that class was managed by `boost::shared_ptr` AND
* you passed one of that class's methods and the `boost::shared_ptr`
specifically to `boost::bind()` AND
* the resulting `boost::bind()` object was passed into `LLEventPump::listen()`
THEN the promise was that on destruction of that object, that listener would
automatically be disconnected -- instead of leaving a dangling pointer bound
into the `LLEventPump`, causing a crash on the next `LLEventPump::post()` call.
The only existing code in the viewer code base that exercised `LLEventTrackable`
functionality was in test programs. When the viewer calls `LLEventPump::listen()`,
it typically stores the resulting connection object in an `LLTempBoundListener`
variable, which guarantees disconnection on destruction of that variable.
The fact that `LLEventTrackable` support is specific to `boost::bind()`, that it
silently fails to keep its promise with `std::bind()` or a lambda or any other
form of C++ callable, makes it untrustworthy for new code.
Note that the code base still uses `boost::signals2::trackable` for other
`boost::signals2::signal` instances not associated with `LLEventPump`. We are
not changing those at this time.
---
indra/test/llevents_tut.cpp | 58 +--------------------------------------------
1 file changed, 1 insertion(+), 57 deletions(-)
(limited to 'indra/test/llevents_tut.cpp')
diff --git a/indra/test/llevents_tut.cpp b/indra/test/llevents_tut.cpp
index 875ca9ad89..f9cc99203b 100644
--- a/indra/test/llevents_tut.cpp
+++ b/indra/test/llevents_tut.cpp
@@ -429,7 +429,7 @@ void events_object::test<9>()
{
set_test_name("listen(boost::bind(...TempListener...))");
// listen() can't do anything about a plain TempListener instance:
- // it's not managed with shared_ptr, nor is it an LLEventTrackable subclass
+ // it's not managed with shared_ptr
bool live = false;
LLEventPump& heaptest(pumps.obtain("heaptest"));
LLBoundListener connection;
@@ -453,60 +453,4 @@ void events_object::test<9>()
heaptest.stopListening("temp");
}
-class TempTrackableListener: public TempListener, public LLEventTrackable
-{
-public:
- TempTrackableListener(const std::string& name, bool& liveFlag):
- TempListener(name, liveFlag)
- {}
-};
-
-template<> template<>
-void events_object::test<10>()
-{
- set_test_name("listen(boost::bind(...TempTrackableListener ref...))");
- bool live = false;
- LLEventPump& heaptest(pumps.obtain("heaptest"));
- LLBoundListener connection;
- {
- TempTrackableListener tempListener("temp", live);
- ensure("TempTrackableListener constructed", live);
- connection = heaptest.listen(tempListener.getName(),
- boost::bind(&TempTrackableListener::call,
- boost::ref(tempListener), _1));
- heaptest.post(1);
- check_listener("received", tempListener, 1);
- } // presumably this will make tempListener go away?
- // verify that
- ensure("TempTrackableListener destroyed", ! live);
- ensure("implicit disconnect", ! connection.connected());
- // now just make sure we don't blow up trying to access a freed object!
- heaptest.post(2);
-}
-
-template<> template<>
-void events_object::test<11>()
-{
- set_test_name("listen(boost::bind(...TempTrackableListener pointer...))");
- bool live = false;
- LLEventPump& heaptest(pumps.obtain("heaptest"));
- LLBoundListener connection;
- {
- TempTrackableListener* newListener(new TempTrackableListener("temp", live));
- ensure("TempTrackableListener constructed", live);
- connection = heaptest.listen(newListener->getName(),
- boost::bind(&TempTrackableListener::call,
- newListener, _1));
- heaptest.post(1);
- check_listener("received", *newListener, 1);
- // explicitly destroy newListener
- delete newListener;
- }
- // verify that
- ensure("TempTrackableListener destroyed", ! live);
- ensure("implicit disconnect", ! connection.connected());
- // now just make sure we don't blow up trying to access a freed object!
- heaptest.post(2);
-}
-
} // namespace tut
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