#include "moar.h"

#define LOG_REPOSSESSIONS 0

/* Creates a new serialization context with the specified handle. If any
 * compilation units are waiting for an SC with this handle, removes it from
 * their to-resolve list after installing itself in the appropriate slot. */
MVMObject * MVM_sc_create(MVMThreadContext *tc, MVMString *handle) {
    MVMSerializationContext     *sc;

    if (!MVM_str_hash_key_is_valid(tc, handle)) {
        MVM_str_hash_key_throw_invalid(tc, handle);
    }

    /* Allocate. */
    MVMROOT(tc, handle, {
        sc = (MVMSerializationContext *)REPR(tc->instance->SCRef)->allocate(tc, STABLE(tc->instance->SCRef));
        MVMROOT(tc, sc, {
            /* Add to weak lookup hash. */
            uv_mutex_lock(&tc->instance->mutex_sc_registry);
            struct MVMSerializationContextWeakHashEntry *entry
                = MVM_str_hash_lvalue_fetch_nocheck(tc, &tc->instance->sc_weakhash, handle);
            if (!entry->hash_handle.key) {
                entry->hash_handle.key = handle;

                MVMSerializationContextBody *scb = MVM_calloc(1, sizeof(MVMSerializationContextBody));
                entry->scb = scb;
                sc->body = scb;
                MVM_ASSIGN_REF(tc, &(sc->common.header), scb->handle, handle);
                /* Calling repr_init will allocate, BUT if it does so, and we
                 * get unlucky, the GC will try to acquire mutex_sc_registry.
                 * This deadlocks. Thus, we force allocation in gen2, which
                 * can never trigger GC. Note that releasing the mutex early
                 * is not a good way to fix this, as it leaves a race to
                 * test/set scb->sc (between the line doing it in this block,
                 * and in the else clauses beneath it). */
                MVM_gc_allocate_gen2_default_set(tc);
                MVM_repr_init(tc, (MVMObject *)sc);
                MVM_gc_allocate_gen2_default_clear(tc);
                scb->sc = sc;
                MVM_sc_add_all_scs_entry(tc, scb);
            }
            else {
                MVMSerializationContextBody *scb = entry->scb;
                if (scb->sc) {
                    /* we lost a race to create it! */
                    sc = scb->sc;
                }
                else {
                    scb->sc = sc;
                    sc->body = scb;
                    MVM_ASSIGN_REF(tc, &(sc->common.header), scb->handle, handle);
                    MVM_gc_allocate_gen2_default_set(tc);
                    MVM_repr_init(tc, (MVMObject *)sc);
                    MVM_gc_allocate_gen2_default_clear(tc);
                }
            }
            uv_mutex_unlock(&tc->instance->mutex_sc_registry);
        });
    });

    return (MVMObject *)sc;
}

/* Makes an entry in all SCs list, the index of which is used to refer to
 * SCs in object headers. This must only be called while holding the SC
 * registry mutex. However, the all SCs list is read without the lock.
 * Thus free allocated memory at a safepoint. */
void MVM_sc_add_all_scs_entry(MVMThreadContext *tc, MVMSerializationContextBody *scb) {
    if (tc->instance->all_scs_next_idx == tc->instance->all_scs_alloc) {
        if (tc->instance->all_scs_next_idx == 0) {
            /* First time; allocate, and NULL first slot as it is
             * the "no SC" sentinel value. */
            tc->instance->all_scs_alloc = 32;
            tc->instance->all_scs    = MVM_malloc(tc->instance->all_scs_alloc * sizeof(MVMSerializationContextBody *));
            tc->instance->all_scs[0] = NULL;
            tc->instance->all_scs_next_idx++;
        }
        else {
            MVMuint32 orig_alloc = tc->instance->all_scs_alloc;
            tc->instance->all_scs_alloc += 32;
            tc->instance->all_scs = MVM_realloc_at_safepoint(tc,
                tc->instance->all_scs,
                orig_alloc * sizeof(MVMSerializationContextBody *),
                tc->instance->all_scs_alloc * sizeof(MVMSerializationContextBody *));
        }
    }
    scb->sc_idx = tc->instance->all_scs_next_idx;
    tc->instance->all_scs[tc->instance->all_scs_next_idx] = scb;
    tc->instance->all_scs_next_idx++;
}

void MVM_sc_all_scs_destroy(MVMThreadContext *tc) {
    MVM_free(tc->instance->all_scs);
}

/* Given an SC, returns its unique handle. */
MVMString * MVM_sc_get_handle(MVMThreadContext *tc, MVMSerializationContext *sc) {
    return sc->body->handle;
}

/* Given an SC, returns its description. */
MVMString * MVM_sc_get_description(MVMThreadContext *tc, MVMSerializationContext *sc) {
    return sc->body->description;
}

/* Given an SC, sets its description. */
void MVM_sc_set_description(MVMThreadContext *tc, MVMSerializationContext *sc, MVMString *desc) {
    MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->description, desc);
}

/* Given an SC, looks up the index of an object that is in its root set. */
MVMint64 MVM_sc_find_object_idx(MVMThreadContext *tc, MVMSerializationContext *sc, MVMObject *obj) {
    MVMObject **roots;
    MVMint64    i, count;
    MVMuint32   cached = MVM_sc_get_idx_in_sc(&obj->header);
    if (cached != ~(unsigned)0 && MVM_sc_get_collectable_sc(tc, &obj->header) == sc)
        return cached;
    roots = sc->body->root_objects;
    count = sc->body->num_objects;
    for (i = 0; i < count; i++)
        if (roots[i] == obj)
            return i;
    MVM_exception_throw_adhoc(tc,
        "Object does not exist in serialization context");
}

/* Calls MVM_sc_find_object_idx, but first checks if the sc is actually an SCRef. */
MVMint64 MVM_sc_find_object_idx_jit(MVMThreadContext *tc, MVMObject *sc, MVMObject *obj) {
    if (REPR(sc)->ID != MVM_REPR_ID_SCRef)
        MVM_exception_throw_adhoc(tc,
            "Must provide an SCRef operand to scgetobjidx");
    return MVM_sc_find_object_idx(tc, (MVMSerializationContext *)sc, obj);
}

/* Given an SC, looks up the index of an STable that is in its root set. */
MVMint64 MVM_sc_find_stable_idx(MVMThreadContext *tc, MVMSerializationContext *sc, MVMSTable *st) {
    MVMuint64 i;
    MVMuint32 cached = MVM_sc_get_idx_in_sc(&st->header);
    if (cached != ~(unsigned)0 && MVM_sc_get_collectable_sc(tc, &st->header) == sc)
        return cached;
    for (i = 0; i < sc->body->num_stables; i++)
        if (sc->body->root_stables[i] == st)
            return i;
    MVM_exception_throw_adhoc(tc,
        "STable %s does not exist in serialization context", MVM_6model_get_stable_debug_name(tc, st));
}

/* Given an SC, looks up the index of a code ref that is in its root set. */
MVMint64 MVM_sc_find_code_idx(MVMThreadContext *tc, MVMSerializationContext *sc, MVMObject *obj) {
    MVMObject *roots;
    MVMint64   i, count;
    MVMuint32 cached = MVM_sc_get_idx_in_sc(&obj->header);
    if (cached != ~(unsigned)0 && MVM_sc_get_collectable_sc(tc, &obj->header) == sc)
        return cached;
    roots = sc->body->root_codes;
    count = MVM_repr_elems(tc, roots);
    for (i = 0; i < count; i++) {
        MVMRegister test;
        MVM_VMArray_at_pos(tc, STABLE(roots), roots, OBJECT_BODY(roots), i, &test, MVM_reg_obj);
        if (test.o == obj)
            return i;
    }

    if (REPR(obj)->ID == MVM_REPR_ID_MVMCode) {
        char *c_name = MVM_string_utf8_encode_C_string(tc, ((MVMCode *)obj)->body.name);
        char *waste[] = { c_name, NULL };
        MVM_gc_allocate_gen2_default_clear(tc);
        MVM_exception_throw_adhoc_free(tc, waste,
            "Code ref '%s' does not exist in serialization context",
                c_name);
    }
    else {
        MVM_gc_allocate_gen2_default_clear(tc);
        MVM_exception_throw_adhoc(tc,
            "Code ref '<NOT A CODE OBJECT>' does not exist in serialization context");
    }
}

/* Given a compilation unit and dependency index, returns that SC. Slow path
 * for when the SC may be NULL. */
MVMSerializationContext * MVM_sc_get_sc_slow(MVMThreadContext *tc, MVMCompUnit *cu, MVMint16 dep) {
    MVMSerializationContext *sc = cu->body.scs[dep];
    if (sc == NULL) {
        MVMSerializationContextBody *scb = cu->body.scs_to_resolve[dep];
        if (!scb)
            MVM_exception_throw_adhoc(tc,
                "SC resolution: internal error");
        sc = scb->sc;
        if (sc == NULL)
            return NULL;
        MVM_ASSIGN_REF(tc, &(cu->common.header), cu->body.scs[dep], sc);
        scb->claimed = 1;
    }
    return sc;
}

/* Checks if an SC is currently in the process of doing deserialization work. */
MVM_STATIC_INLINE MVMint64 sc_working(MVMSerializationContext *sc) {
    MVMSerializationReader *sr = sc->body->sr;
    return sr && sr->working;
}

MVMuint8 MVM_sc_is_object_immediately_available(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    MVMObject **roots = sc->body->root_objects;
    MVMint64    count = sc->body->num_objects;
    if (idx >= 0 && idx < count) {
        if (roots[idx] && !sc_working(sc)) {
            return 1;
        }
    }
    return 0;
}

/* Given an SC and an index, fetch the object stored there. */
MVMObject * MVM_sc_get_object(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    MVMObject **roots = sc->body->root_objects;
    MVMint64    count = sc->body->num_objects;
    if (MVM_LIKELY(idx >= 0 && idx < count))
        return roots[idx] && !sc_working(sc)
            ? roots[idx]
            : MVM_serialization_demand_object(tc, sc, idx);
    else {
        char *c_description = MVM_string_utf8_encode_C_string(tc, sc->body->description);
        char *waste[] = { c_description, NULL };
        MVM_exception_throw_adhoc_free(tc, waste,
            "Probable version skew in pre-compiled '%s' (cause: no object at index %"PRId64")",
            c_description, idx);
    }
}

/* Given an SC and an index, fetch the object stored there, or return NULL if
 * there is none. Does not cause lazy deserialization. */
MVMObject * MVM_sc_try_get_object(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    MVMObject **roots = sc->body->root_objects;
    MVMint64    count = sc->body->num_objects;
    if (idx > 0 && idx < count && !sc_working(sc))
        return roots[idx];
    else
        return NULL;
}

/* Given an SC, an index, and an object, store the object at that index and update
 * its SC index to match. */
void MVM_sc_set_object_op(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx, MVMObject *obj) {
    if (REPR(sc)->ID != MVM_REPR_ID_SCRef)
        MVM_exception_throw_adhoc(tc,
            "Must provide an SCRef operand to scsetobj");
    MVM_sc_set_object(tc, sc, idx, obj);
    if (MVM_sc_get_stable_sc(tc, STABLE(obj)) == NULL) {
        /* Need to claim the SC also; typical case for new type objects. */
        MVMSTable *st = STABLE(obj);
        MVM_sc_set_stable_sc(tc, st, (MVMSerializationContext *)sc);
        MVM_sc_push_stable(tc, (MVMSerializationContext *)sc, st);
    }
}

/* Given an SC, an index, and an object, store the object at that index and update
 * its SC index to match. */
void MVM_sc_set_object(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx, MVMObject *obj) {
    MVM_sc_set_object_no_update(tc, sc, idx, obj);
    MVM_sc_set_idx_in_sc(&obj->header, idx);
}

/* Given an SC, an index, and an object, store the object at that index. Do
 * not update the object's own SC index, however. */
void MVM_sc_set_object_no_update(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx, MVMObject *obj) {
    if (idx < 0)
        MVM_exception_throw_adhoc(tc, "Invalid (negative) object root index %"PRId64"", idx);
    if ((MVMuint64)idx < sc->body->num_objects) {
        /* Just updating an existing one. */
        MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->root_objects[idx], obj);
    }
    else {
        if ((MVMuint64)idx >= sc->body->alloc_objects) {
            MVMint64 orig_size = sc->body->alloc_objects;
            sc->body->alloc_objects *= 2;
            if (sc->body->alloc_objects < (MVMuint64)idx + 1)
                sc->body->alloc_objects = idx + 1;
            sc->body->root_objects = MVM_recalloc(sc->body->root_objects,
                orig_size * sizeof(MVMObject *), sc->body->alloc_objects * sizeof(MVMObject *));
        }
        MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->root_objects[idx], obj);
        sc->body->num_objects = idx + 1;
    }
}

/* Given an SC and an index, fetch the STable stored there. */
MVMSTable * MVM_sc_get_stable(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    if (MVM_LIKELY(idx >= 0 && (MVMuint64)idx < sc->body->num_stables)) {
        MVMSTable *got = sc->body->root_stables[idx];
        return got && !sc_working(sc) ? got : MVM_serialization_demand_stable(tc, sc, idx);
    }
    else {
        char *c_description = MVM_string_utf8_encode_C_string(tc, sc->body->description);
        char *waste[] = { c_description, NULL };
        MVM_exception_throw_adhoc_free(tc, waste,
            "Probable version skew in pre-compiled '%s' (cause: no STable at index %"PRId64")",
            c_description, idx);
    }
}

/* Given an SC and an index, fetch the STable stored there, or return NULL if there
 * is none. Does not cause lazy deserialization. */
MVMSTable * MVM_sc_try_get_stable(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    if (idx >= 0 && (MVMuint64)idx < sc->body->num_stables)
        return sc->body->root_stables[idx];
    else
        return NULL;
}

/* Given an SC, an index, and an STable, store the STable at the index. Does not
 * modify the SC marked on the STable itself. */
void MVM_sc_set_stable(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx, MVMSTable *st) {
    if (MVM_UNLIKELY(idx < 0))
        MVM_exception_throw_adhoc(tc,
            "Invalid (negative) STable index %"PRId64, idx);
    if ((MVMuint64)idx < sc->body->num_stables) {
        /* Just updating an existing one. */
        MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->root_stables[idx], st);
    }
    else {
        if ((MVMuint64)idx >= sc->body->alloc_stables) {
            MVMint64 orig_size = sc->body->alloc_stables;
            sc->body->alloc_stables += 32;
            if (sc->body->alloc_stables < (MVMuint64)idx + 1)
                sc->body->alloc_stables = idx + 1;
            sc->body->root_stables = MVM_recalloc(sc->body->root_stables, orig_size,
                sc->body->alloc_stables * sizeof(MVMSTable *));
        }
        MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->root_stables[idx], st);
        sc->body->num_stables = idx + 1;
    }
}


/* Given an SC and an STable, pushes the STable to the end of the root list. */
void MVM_sc_push_stable(MVMThreadContext *tc, MVMSerializationContext *sc, MVMSTable *st) {
    MVMint64 idx = sc->body->num_stables;
    if ((MVMuint64)idx == sc->body->alloc_stables) {
        sc->body->alloc_stables += 16;
        sc->body->root_stables = MVM_realloc(sc->body->root_stables,
            sc->body->alloc_stables * sizeof(MVMSTable *));
    }
    MVM_ASSIGN_REF(tc, &(sc->common.header), sc->body->root_stables[idx], st);
    sc->body->num_stables++;
}

/* Given an SC and an index, fetch the code ref stored there. */
MVMObject * MVM_sc_get_code(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx) {
    MVMObject *roots = sc->body->root_codes;
    MVMuint64   count = MVM_repr_elems(tc, roots);
    if ((MVMuint64)idx < count) {
        MVMObject *found = MVM_repr_at_pos_o(tc, roots, idx);
        return MVM_is_null(tc, found) || sc_working(sc)
            ? MVM_serialization_demand_code(tc, sc, idx)
            : found;
    }
    else {
        char *c_description = MVM_string_utf8_encode_C_string(tc, sc->body->description);
        char *waste[] = { c_description, NULL };
        MVM_exception_throw_adhoc_free(tc, waste,
            "Probable version skew in pre-compiled '%s' (cause: no code ref at index %"PRId64")",
            c_description, idx);
    }
}

/* Given an SC, an index and a code ref, store it and the index. */
void MVM_sc_set_code_op(MVMThreadContext *tc, MVMSerializationContext *sc, MVMint64 idx, MVMObject *code) {
    if (REPR(sc)->ID != MVM_REPR_ID_SCRef)
        MVM_exception_throw_adhoc(tc,
            "Must provide an SCRef operand to scsetcode");
    MVM_sc_set_obj_sc(tc, code, sc);
    MVM_sc_set_code(tc, sc, idx, code);
}
/* Resolves an SC handle using the SC weakhash. */
MVMSerializationContext * MVM_sc_find_by_handle(MVMThreadContext *tc, MVMString *handle) {
    uv_mutex_lock(&tc->instance->mutex_sc_registry);
    struct MVMSerializationContextWeakHashEntry *entry
        = MVM_str_hash_fetch_nocheck(tc, &tc->instance->sc_weakhash, handle);
    uv_mutex_unlock(&tc->instance->mutex_sc_registry);
    return entry ? entry->scb->sc : NULL;
}

/* Marks all objects, stables and codes that belong to this SC as free to be taken by another. */
void MVM_sc_disclaim(MVMThreadContext *tc, MVMSerializationContext *sc) {
    MVMObject **root_objects, *root_codes, *obj;
    MVMSTable **root_stables, *stable;
    MVMint64 i, count;
    MVMCollectable *col;
    if (REPR(sc)->ID != MVM_REPR_ID_SCRef)
        MVM_exception_throw_adhoc(tc,
            "Must provide an SCRef operand to scdisclaim");

    root_objects = sc->body->root_objects;
    count        = sc->body->num_objects;
    for (i = 0; i < count; i++) {
        obj = root_objects[i];
        col = &obj->header;
#ifdef MVM_USE_OVERFLOW_SERIALIZATION_INDEX
        if (col->flags1 & MVM_CF_SERIALZATION_INDEX_ALLOCATED) {
            struct MVMSerializationIndex *const sci = col->sc_forward_u.sci;
            col->sc_forward_u.sci = NULL;
            MVM_free(sci);
        }
        col->sc_forward_u.sc.sc_idx = 0;
        col->sc_forward_u.sc.idx = 0;
#else
        col->sc_forward_u.sc.sc_idx = 0;
        col->sc_forward_u.sc.idx = 0;
#endif
    }
    sc->body->num_objects = 0;

    root_stables = sc->body->root_stables;
    count        = sc->body->num_stables;
    for (i = 0; i < count; i++) {
        stable                      = root_stables[i];
        col                         = &stable->header;
        col->sc_forward_u.sc.sc_idx = 0;
    }
    sc->body->num_stables = 0;

    root_codes = sc->body->root_codes;
    count      = MVM_repr_elems(tc, root_codes);
    for (i = 0; i < count; i++) {
        obj = MVM_repr_at_pos_o(tc, root_codes, i);
        if (MVM_is_null(tc, obj))
            obj = MVM_serialization_demand_code(tc, sc, i);
        col                         = &obj->header;
        col->sc_forward_u.sc.sc_idx = 0;
    }
    sc->body->root_codes = NULL;
}

/* SC repossession barrier. */
void MVM_SC_WB_OBJ(MVMThreadContext *tc, MVMObject *obj) {
    assert(!(obj->header.flags2 & MVM_CF_FORWARDER_VALID));
    assert(MVM_sc_get_idx_of_sc(&obj->header) != (MVMuint32)~0);
    if (MVM_sc_get_idx_of_sc(&obj->header) > 0 && !(obj->st->mode_flags & MVM_NEVER_REPOSSESS_TYPE))
        MVM_sc_wb_hit_obj(tc, obj);
}

/* Called when an object triggers the SC repossession write barrier. */
void MVM_sc_wb_hit_obj(MVMThreadContext *tc, MVMObject *obj) {
    MVMSerializationContext *comp_sc;

    /* If the WB is disabled or we're not compiling, can exit quickly. */
    if (tc->sc_wb_disable_depth)
        return;
    if (!tc->compiling_scs || !MVM_repr_elems(tc, tc->compiling_scs))
        return;

    /* Same if the object is flagged as one to never repossess. */
    if (obj->header.flags1 & MVM_CF_NEVER_REPOSSESS)
        return;

    /* Otherwise, check that the object's SC is different from the SC
     * of the compilation we're currently in. Repossess if so. */
    comp_sc = (MVMSerializationContext *)MVM_repr_at_pos_o(tc, tc->compiling_scs, 0);
    if (MVM_sc_get_obj_sc(tc, obj) != comp_sc) {
        /* Get new slot ID. */
        MVMint64 new_slot = comp_sc->body->num_objects;

        /* See if the object is actually owned by another, and it's the
         * owner we need to repossess. */
        if (obj->st->WHAT == tc->instance->boot_types.BOOTArray ||
            obj->st->WHAT == tc->instance->boot_types.BOOTHash) {
            MVMObject *owned_objects = MVM_sc_get_obj_sc(tc, obj)->body->owned_objects;
            MVMint64 n = MVM_repr_elems(tc, owned_objects);
            MVMint64 found = 0;
            MVMint64 i;
            for (i = 0; i < n; i += 2) {
                if (MVM_repr_at_pos_o(tc, owned_objects, i) == obj) {
                    MVMSerializationContext *real_sc;
                    obj = MVM_repr_at_pos_o(tc, owned_objects, i + 1);
                    real_sc = MVM_sc_get_obj_sc(tc, obj);
                    if (!real_sc)
                        return; /* Probably disclaimed. */
                    if (real_sc == comp_sc)
                        return;
                    found = 1;
                    break;
                }
            }
            if (!found)
                return;
        }

        /* Add to root set. */
        MVM_sc_set_object(tc, comp_sc, new_slot, obj);

        /* Add repossession entry. */
        MVM_repr_push_i(tc, comp_sc->body->rep_indexes, new_slot << 1);
        MVM_repr_push_o(tc, comp_sc->body->rep_scs, (MVMObject *)MVM_sc_get_obj_sc(tc, obj));

        /* Update SC of the object, claiming it, and update index too. */
        MVM_sc_set_obj_sc(tc, obj, comp_sc);
        MVM_sc_set_idx_in_sc(&(obj->header), new_slot);

#if LOG_REPOSSESSIONS
        fprintf(stderr, "Repossession of object %s\n", obj->st->debug_name);
        MVM_dump_backtrace(tc);
#endif
    }
}

/* Called when an STable triggers the SC repossession write barrier. */
void MVM_sc_wb_hit_st(MVMThreadContext *tc, MVMSTable *st) {
    MVMSerializationContext *comp_sc;

    /* If the WB is disabled or we're not compiling, can exit quickly. */
    if (tc->sc_wb_disable_depth)
        return;
    if (!tc->compiling_scs || !MVM_repr_elems(tc, tc->compiling_scs))
        return;

    /* Otherwise, check that the STable's SC is different from the SC
     * of the compilation we're currently in. Repossess if so. */
    comp_sc = (MVMSerializationContext *)MVM_repr_at_pos_o(tc, tc->compiling_scs, 0);
    if (MVM_sc_get_stable_sc(tc, st) != comp_sc) {
        /* Add to root set. */
        MVMint64 new_slot = comp_sc->body->num_stables;
        MVM_sc_push_stable(tc, comp_sc, st);

        /* Add repossession entry. */
        MVM_repr_push_i(tc, comp_sc->body->rep_indexes, (new_slot << 1) | 1);
        MVM_repr_push_o(tc, comp_sc->body->rep_scs, (MVMObject *)MVM_sc_get_stable_sc(tc, st));

        /* Update SC of the STable, claiming it. */
        MVM_sc_set_stable_sc(tc, st, comp_sc);
        MVM_sc_set_idx_in_sc(&(st->header), new_slot);

#if LOG_REPOSSESSIONS
        fprintf(stderr, "Repossession of STable %s\n", st->debug_name);
        MVM_dump_backtrace(tc);
#endif
    }
}