* Fix passing a negative number as either tv_usec or tv_nsec. When file_time_type
is negative and has a non-zero sub-second value we subtract 1 from tv_sec
and make the sub-second duration positive.
* Detect and report when 'file_time_type' cannot be represented by time_t. This
happens when using large/small file_time_type values with a 32 bit time_t.
There is more work to be done in the implementation. It should start to use
stat's st_mtim or st_mtimeval if it's provided as an extension. That way
we can provide a better resolution.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@273103 91177308-0d34-0410-b5e6-96231b3b80d8
70f7afec38