context_obtain_alloc
struct alloc_cache* context_obtain_alloc(struct ub_ctx* ctx, int locking);
w->env->alloc = context_obtain_alloc(ctx, !w->is_bg || w->is_bg_thread);
struct alloc_cache* context_obtain_alloc(struct ub_ctx* ctx, int locking);
w->env->alloc = context_obtain_alloc(ctx, !w->is_bg || w->is_bg_thread);