Files ===== simplefs.c The most stripped down Tcl FS that I could make. It tests the 'cd' command. It does virtually no checking but should suffice as long as one does not deliberately break it. Compile (on windows) with: gcc -o simplefs simplefs.c -IC:/Progra~1/Tcl/include \ -LC:/Progra~1/Tcl/lib -ltcl86 winvols.c This is the code that Tcl uses to create the windows file system "volumes". It shows that Tcl uses "C:/", "D:/", etc. This (and the code in generic/tclTest.c) tells me that my volume name "zvfs:/" should be valid. What I'm trying to figure out ============================= With tclsh, I can do: % cd d: % pwd D:/ % cd msys64 % pwd D:/msys64 % cd home % pwd D:/msys64/home % cd .. % pwd D:/msys64 % cd .. % pwd D:/ % cd .. % pwd D:/ With my simplefs test program, I (used to) get: % cd d: % pwd D:/ % cd zvfs:/ % pwd zvfs:/ % cd dir % pwd zvfs:/dir % cd another % pwd zvfs:/dir/another % cd .. % pwd zvfs:/dir % cd .. % pwd zvfs: What happened to the root directory '/'? From here on -- until the next "cd zvfs:/" -- Tcl gets messed up Perhaps a related issue. On windows: % cd d: % pwd D:/ With my fs: % cd zvfs: % pwd D:/ Even though I've told Tcl that the cd is valid, it is rejected. Why does not Tcl return "zvfs:/" as the pwd? Update: I've added a FSNormalizePathProc() to detect and correct the bogus path. This is not a real fix. Update 2: Attempting a "cd zvfs:/; cd /" I found Tcl deriving the path "zv/". This is again due to Tcl not handling volume relative fs but assuming that all such fs are windows. (The "zv/" comes from Tcl assuming the cwd is "<drive>:" so "zv" is appended with "/". This can be fixed in FSNormalizePathProc but is again a kludge.