[Tcl-bugs] [ tcl-Bugs-2710920 ] [file tail] gives wrong result

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Bugs item #2710920, was opened at 2009-03-24 23:05
Message generated for change (Comment added) made by dgp
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Category: 37. File System
Group: current: 8.5.6
Status: Open
Resolution: None
Priority: 9
Private: No
Submitted By: Jeff Epler (jepler)
Assigned to: Don Porter (dgp)
Summary: [file tail] gives wrong result

Initial Comment:
This problem occurs on a freshly built 8.5.6 (unmodified) on Ubuntu Hardy and is also seen on 8.5.3-2 on ubuntu jaunty alpha (ubuntu modified).  The bug is not seen in 8.4.16-4ubuntu1 (ubuntu modified) on ubuntu hardy.

In a specific scenario involving [glob] with a trailing slash, the resulting files are treated improperly by [file tail].  An attached script, which can be run by
$ make shell SCRIPT=filetailbug.tcl
demonstrates the problem on my system.

Expected output:
 /bin bin
Actual output:
 /bin {}

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>Comment By: Don Porter (dgp)
Date: 2009-03-26 15:18

Message:

Bug introduced between 8.5.2 and 8.5.3.

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Comment By: Don Porter (dgp)
Date: 2009-03-26 14:19

Message:

Sorry, I was misled by --enable-shared builds.



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Comment By: Don Porter (dgp)
Date: 2009-03-26 13:58

Message:

Further testing indicates that
Tcl 8.5.0 works, while 8.5.1 has
the bug.



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Comment By: Jeff Epler (jepler)
Date: 2009-03-26 13:53

Message:
I'm glad you found how to reproduce it!

I can confirm what dgp says: whether the script is given as an absolute
path or not affects the output.

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Comment By: Don Porter (dgp)
Date: 2009-03-26 13:47

Message:

I can now reproduce the problem with Tcl 8.5.6:

$ make shell SCRIPT=fff.tcl
...
LD_LIBRARY_PATH="`pwd`:${LD_LIBRARY_PATH}"; export LD_LIBRARY_PATH; \
        TCL_LIBRARY="/home/dgp/cvs/tcl8.5.6/library"; export TCL_LIBRARY;
\
        ./tclsh fff.tcl
/opt/ {}

Note that a very similar attempt yields different results:

$ make shell SCRIPT=~/fff.tcl
...
LD_LIBRARY_PATH="`pwd`:${LD_LIBRARY_PATH}"; export LD_LIBRARY_PATH; \
        TCL_LIBRARY="/home/dgp/cvs/tcl8.5.6/library"; export TCL_LIBRARY;
\
        ./tclsh ~/fff.tcl
/opt/ opt

Same script in a different place and accessed via
an absolute path.  So inspired by that difference, try:

$ make shell SCRIPT=`pwd`/fff.tcl
...
LD_LIBRARY_PATH="`pwd`:${LD_LIBRARY_PATH}"; export LD_LIBRARY_PATH; \
        TCL_LIBRARY="/home/dgp/cvs/tcl8.5.6/library"; export TCL_LIBRARY;
\
        ./tclsh /home/dgp/cvs/tcl8.5.6/unix/fff.tcl
/opt/ opt



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Comment By: Jeff Epler (jepler)
Date: 2009-03-25 20:08

Message:
I failed to correctly minimize the test case in my original submission. 
Please see the attached 'fff.tcl' instead of the original attachment.

$ cat fff.tcl 
proc f {} {
    set d [glob -nocomplain /*/]
    set d [lindex $d 0]
    #set d [format %s $d]   # uncommenting this line makes both 8.4 and
8.5 work
    puts stderr [list $d [file tail $d]]
}

f

$ make shell SCRIPT=fff.tcl
LD_LIBRARY_PATH="`pwd`:${LD_LIBRARY_PATH}"; export LD_LIBRARY_PATH; \
	TCL_LIBRARY="/tmp/tcl8.5.6/library"; export TCL_LIBRARY; \
	./tclsh fff.tcl
/mnt/ {}
$ 


----------------------------------------------------------------------

Comment By: Jeff Epler (jepler)
Date: 2009-03-24 23:07

Message:
I am not familiar with the tcl path object, but I attempted to generate
some useful debugging information.  I found that the 'normPathPtr' is an
empty string, and that TclPathpart returns normPathPtr, leading to the
result I am seeing.  Perhaps the problem is occurring earlier at the point
where this path object is constructed?

Breakpoint 3, TclPathPart (interp=0x606400, pathPtr=0x62aa00, 
    portion=TCL_PATH_TAIL) at
/tmp/tcl8.5.6/unix/../generic/tclPathObj.c:596
596			const char *rest = TclGetString(fsPathPtr->normPathPtr);
(gdb) print fsPathPtr->translatedPathPtr->bytes
$32 = 0x636be0 "/bin"
(gdb) print fsPathPtr->normPathPtr->bytes
$33 = 0x7f2ed6902b48 ""
(gdb) next
598			if (strchr(rest, '/') != NULL) {
(gdb) 
601			if (tclPlatform == TCL_PLATFORM_WINDOWS
(gdb) 
605			Tcl_IncrRefCount(fsPathPtr->normPathPtr);
(gdb) 
606			return fsPathPtr->normPathPtr;
(gdb) 
747	}
(gdb) 


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