fix(runtime): guard URLSearchParams shape probe against non-object receivers (Date.toString segv)

[proggeramlug]

Problem

language/expressions/addition/S11.6.1_A2.2_T2.js regressed to a segfault (SIGSEGV, "no output") after #5964.

#5964 made native URLSearchParams methods reachable through dynamic access by probing the receiver in js_native_call_method for append/set/get/has/delete/toString. The probe masks the receiver bits into an *ObjectHeader and calls shape_is_url_search_params, which reads class_id / keys_array / length at ObjectHeader offsets.

But the receiver can be any pointer-tagged value. A Date value is a pointer to a GC_TYPE_DATE_CELL, whose bytes at those offsets are unrelated. Reading keys_array as a pointer and dereferencing its length faulted — so the test's date.toString() + date.toString() (two toString calls, each firing the probe) crashed.

Fix

Gate shape_is_url_search_params on the GC header type: proceed only when the allocation is GC_TYPE_OBJECT. A Date cell, array, buffer, closure, etc. now returns false immediately instead of reading ObjectHeader fields off a foreign layout. This protects every caller of the shared probe, not just the new toString arm — mirroring the is_plain_matcher_object GC-header check already used elsewhere.

Verification

Built on an internal Linux sweep host:

• language/expressions/addition/S11.6.1_A2.2_T2.js passes (was SIGSEGV).
• date.toString() + date.toString() no longer segfaults.
• URLSearchParams dynamic get / toString / size still work (no regression to fix(runtime): #5961 — URLSearchParams methods reachable through dynamic access #5964's fix).
• language/expressions/addition slice is clean; remaining built-ins/Date runtime-fails are pre-existing unrelated gaps (toTemporalInstant, MakeTime precision, etc.).

Refs #5961. Code-only (no version/changelog).

Summary by CodeRabbit

• Bug Fixes
  • Improved safety when handling URL search parameters so invalid or non-object internal values are no longer misidentified.
  • Prevents crashes or incorrect behavior from type-erased/native method checks on unusual pointer-tagged inputs.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: d892c9f3-3148-4665-bf30-c980fa812537

📥 Commits

Reviewing files that changed from the base of the PR and between c2784c9 and 0963635.

📒 Files selected for processing (1)

• crates/perry-runtime/src/url/search_params.rs

📝 Walkthrough

Walkthrough

The shape_is_url_search_params function was updated to add a safety check before performing existing type verification. It now confirms the pointer is large enough to contain a GC header and that the header's obj_type equals GC_TYPE_OBJECT prior to checking class_id and the _entries key.

Changes

Shape Detection Hardening

Layer / File(s)	Summary
GC header validation guard crates/perry-runtime/src/url/search_params.rs	Adds a pointer-size check and GC header obj_type verification (must equal GC_TYPE_OBJECT) before the existing class_id/_entries key checks in shape_is_url_search_params.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• PerryTS/perry#5108: Coercion logic uses try_read_as_search_params, which relies on the same shape_is_url_search_params detector hardened here.
• PerryTS/perry#5650: Similarly adds a GC-type guard before reading a GcHeader in a different brand-probing function to prevent misclassification.
• PerryTS/perry#5964: Also modifies search_params.rs and tightens usage of shape_is_url_search_params for correct native object dispatch.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the runtime fix for guarding URLSearchParams probing against non-object receivers.
Description check	✅ Passed	The description covers the problem, fix, related issue, and verification, which satisfies the template's required information overall.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/t262-regr-date-tostring-segv

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@crates/perry-runtime/src/url/search_params.rs`:
- Around line 830-837: Update shape_is_url_search_params to reject non-object
receivers before any GC-header dereference: the current guard only checks the
object pointer against GC_HEADER_SIZE, but this probe can be called with
type-erased receivers like registered buffers. Add the same raw-receiver
validation used elsewhere (the raw < 0x10000 and is_registered_buffer(raw)
check) before computing gc_header or reading obj_type, so non-object cells are
filtered out safely.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: ab346e3c-bfb4-40e2-8891-40185fdc3847

📥 Commits

Reviewing files that changed from the base of the PR and between 95e4817 and c2784c9.

📒 Files selected for processing (1)

• crates/perry-runtime/src/url/search_params.rs