An exception in the LLSingleton subclass constructor, or in its
initSingleton() method, could leave the LLSingleton machinery in a bad state:
the failing instance would remain in the MasterList, also on the stack of
initializing LLSingletons. Catch exceptions in either and perform relevant
cleanup.
This problem is highlighted by test programs, in which LL_ERRS throws an
exception rather than crashing the whole process.
In the relevant catch clauses, clean up the initializing stack BEFORE logging.
Otherwise we get tangled up recording bogus dependencies.
Move capture_dependency() out of finishInitializing(): it must be called by
every valid getInstance() call, both from LLSingleton and LLParamSingleton.
Introduce new CONSTRUCTED EInitState value to distinguish "have called the
constructor but not yet the initSingleton() method" from "currently within
initSingleton() method." This is transient, but we execute the 'switch' on
state within that moment. One could argue that the previous enum used
INITIALIZING for current CONSTRUCTED, and INITIALIZED meant INITIALIZING too,
but this is clearer.
Introduce template LLSingletonBase::classname() helper methods to clarify
verbose demangle(typeid(stuff).name()) calls.
Similarly, introduce LLSingleton::pop_initializing() shorthand method.
Add try/catch clauses to constructSingleton() (to catch exceptions in the
subclass constructor) and finishInitializing() (to catch exceptions in the
subclass initSingleton() method). Each of these catch clauses rethrows the
exception -- they're for cleanup, not for ultimate handling.
Introduce LLSingletonBase::reset_initializing(list_t::size_t). The idea is
that since we can't know whether the exception happened before or after the
push_initializing() call in LLSingletonBase's constructor, we can't just pop
the stack. Instead, constructSingleton() captures the stack size before
attempting to construct the new LLSingleton subclass. On exception, it calls
reset_initializing() to restore the stack to that size.
Naturally that requires a corresponding LLSingleton_manage_master method,
whose MasterList specialization is a no-op.
finishInitializing()'s exception handling is a bit simpler because it has a
constructed LLSingleton subclass instance in hand, therefore
push_initializing() has definitely been called, therefore it can call
pop_initializing().
Break out new static capture_dependency() method from finishInitializing()
because, in the previous LLSingleton::getInstance() implementation, the logic
now wrapped in capture_dependency() was reached even in the INITIALIZED case.
TODO: Add a new EInitState to differentiate "have been constructed, now
calling initSingleton()" from "fully initialized, normal case" -- in the
latter control path we should not be calling capture_dependency().
The LLSingleton_manage_master<LLSingletonBase::MasterList> specialization's
get_initializing() function (which called get_initializing_from()) was
potentially dangerous. get_initializing() is called by push_initializing(),
which (in the general case) is called by LLSingletonBase's constructor. If
somehow the MasterList's LLSingletonBase constructor ended up calling
get_initializing(), it would have called get_initializing_from(), passing an
LLSingletonBase which had not yet been constructed into the MasterList. In
particular, its mInitializing map would not yet have been initialized at all.
Since the MasterList must not, by design, depend on any other LLSingletons,
LLSingleton_manage_master<LLSingletonBase::MasterList>::get_initializing()
need not return a list from the official mInitializing map anyway. It can, and
should, and now does, return a static dummy list. That obviates
get_initializing_from(), which is removed.
That in turn means we no longer need to pass get_initializing() an
LLSingletonBase*. Remove that parameter.
The recent LLSingleton work added a hook that would run during the C++
runtime's final destruction of static objects. When the LAST LLSingleton in
any module was destroyed, its destructor would call
LLSingletonBase::deleteAll(). That mechanism was intended to permit an
application consuming LLSingletons to skip making an explicit deleteAll()
call, knowing that all instantiated LLSingleton instances would eventually be
cleaned up anyway.
However -- experience proves that kicking off deleteAll() processing during
the C++ runtime's final cleanup is too late. Too much has already been
destroyed. That call tends to cause more shutdown crashes than it resolves.
This commit deletes that whole mechanism. Going forward, if you want to clean
up LLSingleton instances, you must explicitly call
LLSingletonBase::deleteAll() during the application lifetime. If you don't,
LLSingleton instances will simply be leaked -- which might be okay,
considering the application is terminating anyway.
A shocking number of LLSingleton subclasses had public constructors -- and in
several instances, were being explicitly instantiated independently of the
LLSingleton machinery. This breaks the new LLSingleton dependency-tracking
machinery. It seems only fair that if you say you want an LLSingleton, there
should only be ONE INSTANCE!
Introduce LLSINGLETON() and LLSINGLETON_EMPTY_CTOR() macros. These handle the
friend class LLSingleton<whatevah>;
and explicitly declare a private nullary constructor.
To try to enforce the LLSINGLETON() convention, introduce a new pure virtual
LLSingleton method you_must_use_LLSINGLETON_macro() which is, as you might
suspect, defined by the macro. If you declare an LLSingleton subclass without
using LLSINGLETON() or LLSINGLETON_EMPTY_CTOR() in the class body, you can't
instantiate the subclass for lack of a you_must_use_LLSINGLETON_macro()
implementation -- which will hopefully remind the coder.
Trawl through ALL LLSingleton subclass definitions, sprinkling in
LLSINGLETON() or LLSINGLETON_EMPTY_CTOR() as appropriate. Remove all explicit
constructor declarations, public or private, along with relevant 'friend class
LLSingleton<myself>' declarations. Where destructors are declared, move them
into private section as well. Where the constructor was inline but nontrivial,
move out of class body.
Fix several LLSingleton abuses revealed by making ctors/dtors private:
LLGlobalEconomy was both an LLSingleton and the base class for
LLRegionEconomy, a non-LLSingleton. (Therefore every LLRegionEconomy instance
contained another instance of the LLGlobalEconomy "singleton.") Extract
LLBaseEconomy; LLGlobalEconomy is now a trivial subclass of that.
LLRegionEconomy, as you might suspect, now derives from LLBaseEconomy.
LLToolGrab, an LLSingleton, was also explicitly instantiated by
LLToolCompGun's constructor. Extract LLToolGrabBase, explicitly instantiated,
with trivial subclass LLToolGrab, the LLSingleton instance.
(WARNING: LLToolGrabBase methods have an unnerving tendency to go after
LLToolGrab::getInstance(). I DO NOT KNOW what should be the relationship
between the instance in LLToolCompGun and the LLToolGrab singleton instance.)
LLGridManager declared a variant constructor accepting (const std::string&),
with the comment:
// initialize with an explicity grid file for testing.
As there is no evidence of this being called from anywhere, delete it.
LLChicletBar's constructor accepted an optional (const LLSD&). As the LLSD
parameter wasn't used, and as there is no evidence of it being passed from
anywhere, delete the parameter.
LLViewerWindow::shutdownViews() was checking LLNavigationBar::
instanceExists(), then deleting its getInstance() pointer -- leaving a
dangling LLSingleton instance pointer, a land mine if any subsequent code
should attempt to reference it. Use deleteSingleton() instead.
~LLAppViewer() was calling LLViewerEventRecorder::instance() and then
explicitly calling ~LLViewerEventRecorder() on that instance -- leaving the
LLSingleton instance pointer pointing to an allocated-but-destroyed instance.
Use deleteSingleton() instead.
Until we reimplement LLCoros on Boost.Fiber, we must hand-implement
coroutine-local data. That presently takes the form of a map keyed on
llcoro::id, whose values are the stacks of currently-initializing LLSingleton
instances.
But since the viewer launches an open-ended number of coroutines, we could end
up with an open-ended number of map entries unless we intentionally prune the
map. So every time we pop the stack to empty, remove that map entry.
This could result in thrashing, a given coroutine's 'initializing' stack being
created and deleted for almost every LLSingleton instantiated by that
coroutine -- but the number of different LLSingletons is necessarily static,
and the lifespan of each is the entire rest of the process. Even a couple
dozen LLSingletons won't thrash that badly.
The stack we maintain of which LLSingletons are currently initializing only
makes sense when associated with a particular C++ call stack. But each
coroutine introduces another C++ call stack!
Move the initializing stack from function-static storage to
LLSingletonBase::MasterList. Make it a map keyed by llcoro::id. Each coro then
has a stack of its own.
This introduces more dependencies on the MasterList singleton, requiring
additional LLSingleton_manage_master workarounds.
Specifically, add DEBUG logging to the code that maintains the stack of
LLSingletons currently being initialized. This involves passing
LLSingletonBase's constructor the name of LLSingleton's template parameter
subclass, since during that constructor typeid(*this).name() will only produce
"LLSingletonBase".
Also add logdebugs() and oktolog() helper functions.
Specifically, log as LLSingleton captures inter-Singleton dependencies. Also
log cleanupAll() calls to cleanupSingleton() and deleteAll() calls to
deleteSingleton(), since they happen in an implicitly-determined order. But do
not log anything during the implicit LLSingletonBase::deleteAll() call
triggered by the runtime destroying the last LLSingleton's static data. That's
too late in the run; even std::cerr might already have been destroyed!
clang gets nervous about expressions that call functions inside typeid(), even
though these particular typeid() calls are runtime expressions on runtime
values. Extract the offending calls to a previous statement.
LLSingleton explicitly supports circular dependencies: initialization
performed during an LLSingleton subclass's initSingleton() method may
recursively call that same subclass's getInstance() method. On the other hand,
circularity from a subclass constructor cannot be permitted, else
getInstance() would have to return a partially-constructed object.
Our dependency tracking circularity check initially forbade both. Loosen it to
permit references from within initSingleton().
Part of LLError's logging infrastructure is implemented with an LLSingleton.
Therefore, attempts to log from within LLSingleton machinery could potentially
go south if LLError's LLSingleton is not yet initialized.
Introduce LLError::is_available() in llerrorcontrol.h and llerror.cpp.
Make LLSingletonBase::logwarns() and logerrs() consult LLError::is_available()
before attempting to use LL_WARNS or LL_ERRS, respectively.
Moreover, make all LLSingleton internal logging use logwarns() and logerrs()
instead of directly engaging LL_ERRS or LL_WARNS.
Introduce LLSingleton::cleanupSingleton() canonical method as the place to put
any subclass cleanup logic that might take nontrivial realtime or throw an
exception. Neither is appropriate in a destructor.
Track all extant LLSingleton subclass instances on a master list, which
permits adding LLSingletonBase::cleanupAll() and deleteAll() methods.
Also notice when any LLSingleton subclass constructor (or initSingleton()
method) calls instance() or getInstance() for another LLSingleton, and capture
that other LLSingleton instance as a dependency of the first. This permits
cleanupAll() and deleteAll() to perform a dependency sort on the master list,
thus cleaning up (or deleting) leaf LLSingletons AFTER the LLSingletons that
depend on them.
Make C++ runtime's final static destructor call LLSingletonBase::deleteAll()
instead of deleting individual LLSingleton instances in arbitrary order.
Eliminate "llerror.h" from llsingleton.h, a longstanding TODO.
Nat Goodspeed