1142831 - Many potential leaks if |NS_DispatchToMain| fails

Status: NEW

(Core :: XPCOM, defect)

Description

[Eric Rahm [:erahm]]

Coverity indicates there are 72 potential leaks in calls to |NS_DispatchToMainThread|. A quick grep of the codebase indicates there are probably at least 158.

Previously |NS_DispatchToCurrentThread| was fixed to use a deathGrip on the passed in runnable, but |NS_DispatchToMainThread| was left as-is, due to:

> // In the case of failure with a newly allocated runnable with a
> // refcount of zero, we intentionally leak the runnable, because it is
> // likely that the runnable is being dispatched to the main thread
> // because it owns main thread only objects, so it is not safe to
> // release them here.

AFAICT the majority of code does not behave in this way, but a more thorough survey should be performed. Most often the runnable passed in is a simple struct that calls a function in the main thread context.

Possible options:
- Add a deathGrip to |NS_DispatchToMainThread|
- Update all callers to hold an nsComPtr/nsRefPtr to the passed in runnable
- Do something to make coverity ignore this function

Comment 1

[Nicholas Nethercote [inactive]]

Everyone agreed making NS_DispatchToMain infallible is the best path forward here.