julia-gc: Repair the DISABLE_STACK_SCAN build - #6566
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## master #6566 +/- ##
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- Coverage 79.02% 79.02% -0.01%
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Files 683 683
Lines 295189 295189
Branches 8638 8638
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- Hits 233265 233262 -3
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lgoettgens
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That option is meant to turn off conservative stack scanning, but it had come to gate two unrelated things as well, so a build with it defined did not even start. Starting Julia was conditional on it. InitBags calls GAP_InitJuliaMemoryInterface, which is what invokes jl_init(), from a block guarded on stack scanning being enabled; with it disabled the first NewBag dereferenced a null current task. Whether GAP starts Julia depends only on whether GAP is the main program, not on how stacks are scanned. Marking GAP's global bags was conditional on it too. That loop lives in GapRootScanner, and the callback was only installed when stack scanning was enabled, so every global root - the symbol table among them - was collected on the first GC. Install the root scanner either way and guard only the stack walk inside it; scanning other tasks' stacks stays conditional, being purely conservative. With both separated, a DISABLE_STACK_SCAN build starts and runs into genuine rooting gaps rather than into this. Co-authored-by: Claude Opus 5 <noreply@anthropic.com> Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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That option is meant to turn off conservative stack scanning, but it had come to gate two unrelated things as well, so a build with it defined did not even start.
Starting Julia was conditional on it.
InitBagscallsGAP_InitJuliaMemoryInterface, which is what invokesjl_init, from a block guarded on stack scanning being enabled. With it disabled the firstNewBagdereferenced a null current task. Whether GAP starts Julia depends only on whether GAP is the main program, not on how stacks are scanned.Marking GAP's global bags was conditional on it too. That loop lives in
GapRootScanner, and the callback was only installed when stack scanning was enabled, so every global root (the symbol table among them) was collected on the first GC. Install the root scanner either way and guard only the stack walk inside it; scanning other tasks' stacks stays conditional, being purely conservative.With both separated, a
DISABLE_STACK_SCANbuild starts and runs into genuine rooting gaps rather than into this.Co-Authored-By: Claude Fable 5.1 noreply@anthropic.com