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Fix VALIDATE_MARKING in the Julia GC integration #6525

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Merged
fingolfin merged 1 commit into from
Aug 31, 2026
Merged

Fix VALIDATE_MARKING in the Julia GC integration #6525

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34 changes: 20 additions & 14 deletions src/julia_gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -279,16 +279,28 @@ static inline int JMarkTyped(jl_ptls_t ptls, void * obj, jl_datatype_t * ty)
return jl_gc_mark_queue_obj(ptls, (jl_value_t *)obj);
}

// Check that `obj` is still allocated and not on a free list already,
// by verifying that its type is a valid datatype object. A datatype is
// either a pool object, or lives in a system or package image (e.g. the
// types of GAP.jl bags after loading it from a precompiled image), as
// indicated by the `in_image` bit in its header.
static inline int ValidTypeOfMarkedObj(void * obj)
{
jl_value_t * ty = jl_typeof(obj);
// for a freed pool object, `ty` is the freelist link: NULL or a
// pointer into a pool page; check before dereferencing it
if (ty == NULL)
return 0;
if (jl_gc_internal_obj_base_ptr(ty) != ty &&
!jl_astaggedvalue(ty)->bits.in_image)
return 0;
return jl_typeis(ty, jl_datatype_type);
}

static inline int JMark(jl_ptls_t ptls, void * obj)
{
#ifdef VALIDATE_MARKING
// Validate that `obj` is still allocated and not on a
// free list already. We verify this by checking that the
// type is a pool object of type `jl_datatype_type`.
jl_value_t * ty = jl_typeof(obj);
if (jl_gc_internal_obj_base_ptr(ty) != ty)
abort();
if (!jl_typeis(ty, jl_datatype_type))
if (!ValidTypeOfMarkedObj(obj))
abort();
#endif
return jl_gc_mark_queue_obj(ptls, (jl_value_t *)obj);
Expand All @@ -299,13 +311,7 @@ void MarkJuliaObjSafe(void * obj, void * ref)
{
if (!obj)
return;
// Validate that `obj` is still allocated and not on a
// free list already. We verify this by checking that the
// type is a pool object of type `jl_datatype_type`.
jl_value_t * ty = jl_typeof(obj);
if (jl_gc_internal_obj_base_ptr(ty) != ty)
return;
if (!jl_typeis(ty, jl_datatype_type))
if (!ValidTypeOfMarkedObj(obj))
return;
if (jl_gc_mark_queue_obj(((MarkData *)ref)->ptls, (jl_value_t *)obj))
((MarkData *)ref)->youngRef++;
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