On Mar 18, 2010, at 8:43 PM, Ion Gaztañaga wrote:
El 18/03/2010 16:55, Andy Wiese escribió:
Many processes will both read and write this index map. Do the interprocess:: containers provide the needed synchronization, or do I need other synchronization mechanisms?
You need to provide them. Interprocess memory allocation (via construct<>, or allocate(), or through allocators) is thread-safe, just like ::new is thread safe for inter-thread programming. But similarly to inter-thread programming interprocess::map offers the same guarantees as std::map, because interprocess containers are standard-conforming containers: you must provide your own synchronization if you use the same object by two processes-theads and one is inserting or erasing elements.
Best,
Ion
Thank you. That makes perfect sense and is now proven by my test program. I have a couple of questions about crash protection, which is very important in this case: 1. I am using only file_lock, because it is guaranteed to be released if the process crashes (if I understand correctly). However, file_lock has its limitations. If I use a named_recursive_mutex instead, is there any way to clear the mutex if the process terminates while holding the mutex? 2. If the mapped file gets corrupted, e.g. if a process gets killed while writing the file, I need to be able to detect that case and rebuild the file, but the file is certain death to any process that touches it, so validating it seems messy. Any suggestions how to detect a bad file? Andy