[Tcl-bugs] [ tcl-Bugs-411825 ] Passing list w/UTF-8 from C can fail

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Bugs item #411825, was updated on 2001-03-27 22:36
You can respond by visiting: 
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Category: UTF-8 Strings
Group: 8.3.1
Status: Open
Priority: 5
Submitted By: Adrian Robert (arobert3434)
Assigned to: Nobody/Anonymous (nobody)
Summary: Passing list w/UTF-8 from C can fail

Initial Comment:
On certain installations of Tcl/Tk 8.3.1, the passing
of UTF-8
character-triplets ending in octal 240 (decimal 160,
hex A0)
interferes with list delimitation when
Tcl_AppendElement is used
to return a result from a C function.  In particular,
if a UTF-8
string ending in octal 240 is appended to the result,
and then
another UTF-8 string is appended afterwards, the octal
240 seems
to be interpreted as a "forward delete" character of
some kind,
with the result that the separation between the two
list elements
is erased and they are interpreted as one.

The following C function, when called from Tcl,
illustrates the
problem.

int sendCharList(ClientData clientData, Tcl_Interp *interp,
                 int argc, char **argv)
{
    char s1[5], s2[5], s3[5], s4[5];

    strcpy(s1, "\345\220\240");
    strcpy(s2, "\345\214\240");
    strcpy(s3, "\351\235\240");
    strcpy(s4, "\347\264\240");

    Tcl_ResetResult(interp);

    Tcl_AppendElement(interp, s1);
    Tcl_AppendElement(interp, s2);
    Tcl_AppendElement(interp, s3);
    Tcl_AppendElement(interp, s4);

  return TCL_OK;
}

The Tcl calls:

set s6 [sendCharList]
puts "[llength $s6] , [string length $s6]"

should output "4 , 7" (4 list elements, each a single UTF-8
composite character plus 3 delimiters).  On some
systems it does.
On others, however, the output is "1 , 4", resulting from
deletion of the list delimiters somewhere during
passage from C
to Tcl.  A complete test program involving the above
(plus some
additional tests and using wish not tclsh) may be
accessed at:
ftp://zakros.ucsd.edu/arobert/Temp/testTclBug.tgz (it
is also
attached).

A full application that exposes the bug (and led to its
discovery) may be found at:
http://freshmeat.net/projects/hanzim

Unfortunately, I have not been able to isolate why some
installations exhibit the bug and some don't.  A
default SUSE 7.0
Linux installation of 8.3.1 had the problem, while a
default
Slackware 7.1 installation of the same Tcl/Tk version
did not.
Maybe it is a compilation flag difference... ?

I'm also not sure whether it persists in 8.3.2 or 8.4.



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