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Prior to this patch, the code marked a Debugger if any of its debuggee globals
were marked, and it had breakpoints set in JSScripts/Instances that were marked.
It cleaned up breakpoints by scanning all JSScripts and wasm::Instances in the
zones being collected, looking for breakpoints set in them, and deleting them if
either the JSScript/Instance or the owning Debugger was about to be finalized.
That byzantine approach is equivalent to having owning edges from
JSScripts/Instances to the breakpoints set in them, and from those breakpoints
to the Debuggers they belong to. Proof: if a script is live, then its global
must be live. If the script has a breakpoint set in it, and its global is live,
then its Debugger will be marked, and hence neither the Debugger nor the script
will be finalized, and hence the breakpoints will be retained.
That second approach handles the situation with a much more traditional tracing
process, wherein tracing a script traces its breakpoints, which traces their
owning Debuggers. We can simply use cross-compartment wrappers for the edges
from the breakpoints to their handlers and Debuggers, which removes a bunch of
special cases for the GC to worry about.
This patch changes things to use the second approach.
- js::DebugScript and js::wasm::DebugState get `trace` and `finalize`/`delete_`
methods, which get called from the right places. DebugScript and DebugState
become the owners of their `BreakpointSite`s.
- `BreakpointSite`s get `trace` and `finalize` methods that visit their
`Breakpoint`s. `JSBreakpointSite`s also trace their scripts, and
`WasmBreakpointSite`s trace their wasm::Instances.
- `Breakpoint`s get a `trace` method that traces their owning `Debugger` and
their handler object. They hold these as cross-compartment references, since
the `Breakpoint` logically belongs to its code's compartment. Code that uses
these fields wraps/unwraps as appropriate.
- All the specialized breakpoint sweeping code is deleted:
- `Zone::sweepBreakpoints` and its supporting `DebugAPI` functions are
deleted.
- `Debugger::hasAnyLiveHooks` no longer considers breakpoints.
- `DebugAPI::markIteratively` no longer searches for breakpoints to mark.
- `DebugAPI::traceAllForMovingGC` no longer traverses breakpoints.
Differential Revision: https://phabricator.services.mozilla.com/D49858
--HG--
extra : moz-landing-system : lando
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| rust | ||
| src | ||
| xpconnect | ||
| app.mozbuild | ||
| ffi.configure | ||
| moz.build | ||
| moz.configure | ||
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