src: fix null pointer call when running without a startup snapshot - #65820
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src: fix null pointer call when running without a startup snapshot#65820codebytere wants to merge 1 commit into
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Without a startup snapshot (`--no-node-snapshot`, a `--without-node-snapshot` build, or an embedder Environment that was bootstrapped from scratch) starting a Worker made a member call through a null `SnapshotData*`, and so did `NodeMainInstance` while setting itself up. It only worked because the function called does not touch `this`; UBSan reports it for every such Worker. The call existed because `IsolateData::CreateIsolateData()` took an `EmbedderSnapshotData*` and unwrapped it straight away, so the two internal callers wrapped their possibly-null `SnapshotData*` with `AsEmbedderWrapper()` only for it to be unwrapped again. Let the internal function take the `SnapshotData*` itself, unwrap in the public `CreateIsolateData()` only, and drop `AsEmbedderWrapper()`, which has no other users. Refs: nodejs#47731 Signed-off-by: Shelley Vohr <shelley.vohr@gmail.com>
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #65820 +/- ##
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- Coverage 90.19% 90.17% -0.03%
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Files 770 770
Lines 264410 264410
Branches 50243 50232 -11
==========================================
- Hits 238490 238437 -53
- Misses 16924 16979 +55
+ Partials 8996 8994 -2
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Without a startup snapshot (
--no-node-snapshot, a--without-node-snapshotbuild, or an embedder Environment bootstrapped from scratch, which includes Electron's renderer), starting a Worker makes a member call through a nullSnapshotData*, and the main instance does the same while setting itself up. It only works because the function called happens not to touchthis; it is undefined behaviour, and UBSan reports it for every such Worker (node_worker.cc:211: runtime error: member call on null pointer of type 'node::SnapshotData').The call exists because
IsolateData::CreateIsolateData()took anEmbedderSnapshotData*parameter and unwrapped it straight away, so its two internal callers wrapped their possibly-nullSnapshotData*withAsEmbedderWrapper()only for it to be unwrapped again.IsolateData::CreateIsolateData()now takes theSnapshotData*itself and only the publicCreateIsolateData()unwraps the embedder type, so there is no call left to make on a null pointer.AsEmbedderWrapper()had no other users and is removed.Tests:
EnvironmentTest.WorkerInEnvironmentWithoutSnapshotstarts a Worker from the snapshot-less cctest Environment; UBSan flags it before the change and is quiet after.node --no-node-snapshotwith a Worker, and the worker and snapshot test suites, pass.Refs: #47731
Disclosure: the code, test and this description were written by Claude Code, directed and reviewed by @codebytere.