We are getting a crash in filesystem-9.5, 9.6 and 9.7 on Windows XP and Windows 7 with core-8-5-branch.
I bisected the commits and this fault was introduced by the commit on 2009-08-20 by dgp:
"* generic/tclPathObj.c: [Bug 2806250] Prevent the storage of strings ..."
The relevant part of the call stack looks like this:
The crash occurs because in Tcl_DuplicateObj the objPtr->length is -1
I've checked on Windows XP and Windows 7 each time using MSVC6 to compile.