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Bug 1867358 part 4: Add some release asserts (and upgrade an existing assert), to validate that NotificationController isn't still registered as a refresh observer when it's destroyed. r=eeejay

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If these assertions somehow fail, then we are probably doomed to crash anyway.
The new release assertions just make it so we'll crash in a controlled way,
with a more actionable backtrace, closer to the problem-spot.

This patch also removes one mDocument null-check that's becoming redundant
since it follows a release-assert that would make us abort if the pointer is
null.

Differential Revision: https://phabricator.services.mozilla.com/D195042
This commit is contained in:
Daniel Holbert
2023-12-01 17:18:24 +00:00
parent 2db33fc30d
commit f0d8e9467b
1 changed files with 16 additions and 4 deletions
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20
accessible/base/NotificationController.cpp
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@@ -45,6 +45,8 @@ NotificationController::~NotificationController() {
if (mDocument) {
Shutdown();
}
MOZ_RELEASE_ASSERT(mObservingState == eNotObservingRefresh,
"Must unregister before being destroyed");
}
////////////////////////////////////////////////////////////////////////////////
@@ -83,8 +85,13 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
void NotificationController::Shutdown() {
if (mObservingState != eNotObservingRefresh &&
mPresShell->RemoveRefreshObserver(this, FlushType::Display)) {
// Note, this was our last chance to unregister, since we're about to
// clear mPresShell further down in this function.
mObservingState = eNotObservingRefresh;
}
MOZ_RELEASE_ASSERT(mObservingState == eNotObservingRefresh,
"Must unregister before being destroyed (and we just "
"passed our last change to unregister)");
// Shutdown handling child documents.
int32_t childDocCount = mHangingChildDocuments.Length();
@@ -674,12 +681,17 @@ void NotificationController::WillRefresh(mozilla::TimeStamp aTime) {
AUTO_PROFILER_LABEL("NotificationController::WillRefresh", A11Y);
// If the document accessible that notification collector was created for is
// now shut down, don't process notifications anymore.
NS_ASSERTION(
// If mDocument is null, the document accessible that this notification
// controller was created for is now shut down. This means we've lost our
// ability to unregister ourselves, which is bad. (However, it also shouldn't
// be logically possible for us to get here with a null mDocument; the only
// thing that clears that pointer is our Shutdown() method, which first
// unregisters and fatally asserts if that fails).
MOZ_RELEASE_ASSERT(
mDocument,
"The document was shut down while refresh observer is attached!");
if (!mDocument || ipc::ProcessChild::ExpectingShutdown()) {
if (ipc::ProcessChild::ExpectingShutdown()) {
return;
}