Pronto is a new NVMM library that reduces the programming effort required to add persistence to volatile data structures using asynchronous semantic logging (ASL). ASL is generic enough to allow programmers to add persistence to the existing volatile data structure (e.g., C++ Standard Template Library containers) with very little programming effort. Furthermore, ASL moves most durability code off the critical path, and our evaluation shows Pronto data structures outperform highly-optimized NVMM data structures written with other libraries by a large margin.