Saturday, 12 October 2013

Memory management myths: determinism

Although the vast majority of programmers have now migrated to garbage collected languages and will probably never go back, there are still a few clinging to manual memory management. In most cases, the continued use of manual memory management is for good reason but some of these people are perpetuating myths in an attempt to justify avoiding garbage collection. Determinism can be a genuinely good reason to stick with manual memory management and is practically important in memory-constrained embedded devices. However, C++ programs are not as deterministic as people sometimes claim and, in particular, thread-safe reference counting using shared_ptr is non-deterministic. Specifically, threads holding references to shared reference-counted objects race to perform the final decrement and the thread that wins the race is responsible for destruction.