[ASDAlexander77]

Summary

Built ahead of time under -mm=rc, none or own, any program that awaits anything failed to link. The first failure seen was DefaultLib's sleep.ts under rc:

TypeScriptAsyncRuntime.lib(AsyncRuntime.obj) : error LNK2019: unresolved external symbol
GC_allow_register_threads referenced in function GC_enable_threads

GC_register_my_thread, GC_unregister_my_thread and GC_get_stack_base were missing too.

Why the collector's functions were in an rc build

• What's there: since Reference counting memory model (-mm=rc) and related codegen/runtime fixes #308, the async runtime registers its pool threads with the collector under gc (AsyncGCThreads.h). Without that, Boehm's allocator runs unlocked across threads, and a long chain of awaits faulted.
• Why it's harmless at run time: under the other models that code never runs. It switches on only through GC_enable_threads, and only the GC pass injects that call.
• Why it broke the link: the code sat in the scheduler's own object file, which every async program links, and only gc programs link gc.lib. So the linker needed the collector's thread functions in programs that don't have a collector.
• Regression: none linked before Reference counting memory model (-mm=rc) and related codegen/runtime fixes #308.
• Why the JIT didn't show it: TypeScriptRuntime.dll has the collector built in.

Fix

• The split: GC_enable_threads and the collector calls move to an object file of their own, AsyncGCThreadsCommon.inc. It's built as AsyncGCThreads.cpp in both TypeScriptAsyncRuntime and TypeScriptRuntime.
• The hooks: the scheduler reaches that code through two hooks that GC_enable_threads installs. Only the call in a gc program pulls the object in.
• The scheduler no longer includes gc.h.

The archive now shows the split: AsyncRuntime.obj references no GC_* function, and only AsyncGCThreads.obj does.

Tests

test-runner links every model with lld and gc.lib itself. That's why the rc and none corpus runs of 00async_await.ts passed.

The new test-compile-async-without-collector (async-without-collector.cmake, Windows) builds 00async_await.ts with tslang --emit=exe under rc, none and own, with GC_LIB_PATH cleared, and runs it.

Results

Release ctest	3313/3313
00async_await.ts, tslang --emit=exe, gc/rc/none/own at -O0 and -O3	builds and runs (rc/none/own failed to link before)
DefaultLib sleep.ts, rc / none / gc	builds and runs
00async_gc_threading.ts under gc, 20 runs at -O0 and at -O3	0 failures (about 6 in 10 at -O0 without the registration)

Not in this PR

• weakref_basic under rc: DefaultLib's WeakRef calls Boehm's weak-link API directly, and the test calls GC_gcollect() itself. That's a DefaultLib change, and an rc design question (rc document §9.8).
• Linux: the same split applies to the static library there. The new test is Windows-only.

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