C++ client: ::mmap() gets called with length 0

[denizevrenci]

In C++ client implementation, the constructor of MemoryMappedFile calls ::fstat() to get the size of the CnC file. I get a return value of 0 so the function does not fail. However, file size obtained from here is also 0 if I start the driver while the Aeron directory does not exist and start the clients immediately (under 0.1 s) after that. If I wait for 1 s before starting the clients, the probability drops; however, I still occasionally get the resulting exception.

When I checked the call stack, previously Aeron::mapCncFile() gets called. Here the function waits until MemoryMappedFile::getFileSize() returns a non-negative value. However, it does not wait to get a positive filesize.

Is this expected behaviour? In that case, what do I need to do to ensure I do not get an exception without an arbitrary wait period between Aeron driver and client startup?

[mjpt777]

Thanks @denizevrenci. This is not expected behaviour, it is a bug. I'm surprised we have not seen this before. I've pushed fixes for the C++ and Java implementations.

[denizevrenci]

Thank you for the quick fix.