#2322 canvas postscript command core dumps on special polygon

[Anonymous]

Hi,

there is a bug in tkCanvPoly.c:PolygonToPostscript in
recent Tk Versions (tested 8.3.5, 8.4.2).

Create a polygon with two identical points and no
outline color (I know this seems to be nonsense,
but in my case it was absolutely needed).
Do a postscript command on the canvas and you get the
core dump (a color
NULL pointer is passed on from PolygonToPostscript to
Tk_PostscriptColor, where it is referenced)

15:09[wilm@rubin:ConStruct3]$ wish
.wishrc .wishrc .wishrc ...
% canvas .c
.c
% pack .c
% .c create polygon 10 20 10 20
1
% .c postscript
Segmentation fault

Setting the outline sets the color pointer to non-NULL:

15:41[wilm@rubin:ConStruct3]$ wish
.wishrc .wishrc .wishrc ...
% canvas .c
.c
% pack .c
% .c create polygon 10 20 10 20 -outline black
1
% .c postscript
%!PS-Adobe-3.0 EPSF-3.0
...

To avoid this create a polygon with 3 points (using two
different points
activates expansion to three points and cirumvents the
faulty if-clause as well):

16:04[wilm@rubin:ConStruct3]$ wish
.wishrc .wishrc .wishrc ...
% canvas .c
.c
% pack .c
% .c create polygon 10 20 10 20 10 20
1
% .c postscript
%!PS-Adobe-3.0 EPSF-3.0
...

The reason for this bu is the following:
If only two points exist, special case code is used to
create a line and the color
is not verfified to be valid.

To patch this just check if color==NULL in case
polyPtr->numPoints==2 and return TCL_OK
See attachment.

Andreas

[Nobody/Anonymous]

patch

[Donal K. Fellows]

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user_id=79902

While serious, this is not a bug in Tcl. Please resubmit to
the tktoolkit project.