id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
5850	last_write_time on Windows may not work on SMB2-network-mounted drive	Ken Harris <kharris@…>	Beman Dawes	"Consider the following logical operation against a file on a network-mounted drive served over SMB2:

1. fopen(""r+b"")/fwrite/fclose a file.
2. boost::filesystem::last_write_time(file, some other specific time)
3. fopen(""rb"")/fclose a file.

As soon as the file is opened in step 3, it appears that the SMB2/redirector actually closes the file and ""flushes"" its pending write in service of step 1. This has the effect of overwriting the time modification in step 2.

I believe this is happening because boost's non-POSIX/Windows implementation of last_write_time uses CreateFile() and asks only for FILE_WRITE_ATTRIBUTES. Using GENERIC_WRITE appears to work correctly.

Also note, calling utime() instead of boost::filesystem::last_write_time() works correctly. 

Please see attached test code demonstrating boost's failure, utime()'s success, and native API workaround.

Please feel free to contact me for follow up.
Thanks,
-Ken"	Bugs	assigned	To Be Determined	filesystem	Boost 1.47.0	Problem		last_write_time network file	cnewbold@…