gc-ext: only sweep unmarked objects (#45035)

This prior conditional was a fixed constant branch, so this seems more like the intent.

src/gc.c

@@ -556,20 +556,21 @@ JL_DLLEXPORT void jl_finalize_th(jl_task_t *ct, jl_value_t *o)
  arraylist_free(&copied_list);
 }
 
+// explicitly scheduled objects for the sweepfunc callback
 static void gc_sweep_foreign_objs_in_list(arraylist_t *objs)
 {
  size_t p = 0;
  for (size_t i = 0; i < objs->len; i++) {
- jl_value_t *v = (jl_value_t *)(objs->items[i]);
- jl_datatype_t *t = (jl_datatype_t *)(jl_typeof(v));
+ jl_value_t *v = (jl_value_t*)(objs->items[i]);
+ jl_datatype_t *t = (jl_datatype_t*)(jl_typeof(v));
  const jl_datatype_layout_t *layout = t->layout;
  jl_fielddescdyn_t *desc = (jl_fielddescdyn_t*)jl_dt_layout_fields(layout);
- if (!gc_ptr_tag(v, 1)) {
+
+ int bits = jl_astaggedvalue(v)->bits.gc;
+ if (!gc_marked(bits))
  desc->sweepfunc(v);
- }
- else {
+ else
  objs->items[p++] = v;
- }
  }
  objs->len = p;
 }

test/gcext/gcext.c

@@ -561,8 +561,10 @@ void sweep_stack_data(jl_value_t *p)
 {
  obj_sweeps++;
  dynstack_t *stk = (dynstack_t *)p;
- if (stk->size > stk->capacity)
- jl_error("internal error during sweeping");
+ if (stk->size > stk->capacity) {
+ assert(0 && "internal error during sweeping");
+ abort();
+ }
 }
 
 // Safely execute Julia code