JavaScript:SpiderMonkey:GC Futures: Difference between revisions

JavaScript:SpiderMonkey:GC Futures (view source)

499 bytes added , 19 May 2010

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-=== Compartments and wrappers - internal details ===
+=== Compartments and wrappers - implementation details ===
-A context is always "running in" a given compartment, normally the compartment of JS_GetScopeChain(cx). So, for example, <code>js_Atomize(cx, name, strlen(name), 0)</code> allocates the new string in whatever compartment cx is in.
+Each runtime has a ''default compartment'' which contains interned strings (and, in non-compartment-aware embeddings, everything else).
-A consequence of this is that the API function <code>JS_SetProperty(cx, obj, name, vp)</code> must put cx into obj's compartment before calling <code>js_Atomize</code>.
+Each context has a ''current compartment'', initially the default compartment, and normally the compartment of JS_GetScopeChain(cx). So, for example, <code>js_Atomize(cx, name, strlen(name), 0)</code> allocates the new string from <code>cx->currentCompartment()</code>.
+A tricky consequence of this is that the API function <code>JS_SetProperty(cx, obj, name, vp)</code> must put cx into obj's compartment before calling <code>js_Atomize</code>. Otherwise obj might end up with property ids in other compartments, a bad scene.
+When does a context's current compartment change? At API entry points and when a function is called across compartment boundaries (which always happens via a wrapper). So it will be rare and will not ordinarily happen on trace.