Define a new RAII class, AutoDebuggerJobQueueInterruption, to save and restore
the current ECMAScript job queue, to protect the debuggee's job queue from
activity that occurs in debugger callbacks. Add a new method to the JS::JobQueue
abstract base class, saveJobQueue, to support AutoDebuggerJobQueueInterruption.
Comments on AutoDebuggerJobQueueInterruption provide details.
Implement saveJobQueue for SpiderMonkey's internal job queue and for Gecko's job
queue in CycleCollectedJSContext.
Differential Revision: https://phabricator.services.mozilla.com/D17546
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extra : moz-landing-system : lando
While the behavior of ECMAScript Promises and their associated job queue is
covered by the ECMAScript standard, the HTML specification amends that with
additional behavior the web platform requires. To support this, SpiderMonkey
provides hooks the embedding can set to replace SpiderMonkey's queue with its
own implementation.
At present, these hooks are C-style function-pointer-and-void-pointer pairs,
which are awkward to handle and mistake-prone, as passing a function the wrong
void* is not a type error. Later patches in this series must add new hooks,
making a bad situation worse.
A C++ abstract base class is a well-typed alternative. This introduces a new
`JS::JobQueue` abstract class, and adapts SpiderMonkey's internal job queue and
Gecko's customization to use it. `GetIncumbentGlobalCallback` and
`EnqueuePromiseJobCallback` become virtual methods.
Within SpiderMonkey, the patch gathers the various fields of JSContext that
implement the internal queue into their own type, js::InternalJobQueue. Various
jsfriendapi functions become veneers for calls to methods specific to the
derived class. The InternalJobQueue type itself remains private to SpiderMonkey,
as it uses types like TraceableFifo, derived from Fifo, that are not part of
SpiderMonkey's public API.
Within Gecko, CycleCollectedJSContext acquires JS::JobQueue as a private base
class, and a few static methods are cleaned up nicely.
There are a few other hooks defined in js/public/Promise.h that might make sense
to turn into virtual methods on JobQueue. For example,
DispatchToEventLoopCallback, used for resolving promises of results from
off-main-thread tasks, is probably necessarily connected to the JobQueue
implementation in use, so it might not be sensible to set one without the other.
But it was left unchanged to reduce this patch's size.
Differential Revision: https://phabricator.services.mozilla.com/D17544
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extra : moz-landing-system : lando
Move js/src/jsapi.h declarations related to promises and job queues into their
own public header file, js/public/Promise.h. Change the compilation units that
need these declarations to #include the new header.
There should be no changes to the actual functionality here, simply moving the
code to a new file, and removing the "JS" prefix from some typedefs which are
now in the JS namespace.
Differential Revision: https://phabricator.services.mozilla.com/D13345
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extra : moz-landing-system : lando
