Fix source manager lifetime race

[aleksandr-voitenko]

Description

Fix a source lifetime race when reading OBS source properties concurrently with the source’s final release.

Motivation

GetProperties could retrieve a raw obs_source_t * shortly before OBS destroyed its reference control block. Attempting to acquire a strong reference through that stale pointer could crash the backend, as observed in the concurrent browser-source test on macOS.

Context

Locking the source manager around the raw-pointer lookup was insufficient because the manager did not retain an OBS reference. The source could begin destruction before the manager received its destroy callback.

The manager now retains a weak OBS reference for each registered source. GetProperties promotes that weak reference to a strong reference while holding the manager lock. If destruction has already started, it returns InvalidReference.

Implementation details

• Retain weak OBS references alongside registered source IDs.
• Remove weak references during free() and clear().
• Avoid duplicate registrations for the same source.
• Use weak-reference promotion in GetProperties.
• Add a deterministic regression test covering both race outcomes:
  • Final release wins and lookup returns InvalidReference.
  • Lookup wins and keeps the source alive until the operation completes.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

[Copilot]

🟡 Changes recommended

Private scenes can retain weak references indefinitely because their allocation path lacks destroy-signal registration.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Fixes a race between source-property lookup and final source release.

Changes:

• Retains weak source references and promotes them safely.
• Prevents duplicate source registrations.
• Adds deterministic lifecycle regression tests.

File summaries

File	Description
obs-studio-server/source/osn-source.hpp	Adds weak-reference lifecycle management.
obs-studio-server/source/osn-source.cpp	Uses safe promotion in GetProperties.
obs-studio-server/tests/test-osn-source.cpp	Tests both race outcomes.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Balanced

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[Copilot]

🟢 Approval recommended

The lifetime fix is coherent, cleanup paths are covered, and deterministic tests validate both race outcomes.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0 new
• Review effort level: Balanced