Re: [Plplot-devel] comprehensive testing results on Cygwin [POSSIBLE SOLUTION?]

[Arjen M. <Arj...@de...>]

Hi Alan,



> -----Original Message-----
> From: Alan W. Irwin [mailto:ir...@be...]
>
> And after a lot of complaints about shapelib being missing I ran into the following
> peculiar matrix operator message:
>
> [...]
> *** PLPLOT WARNING ***
> plmaptex is a no-op because shapelib is not available.
> No matrix operator named "62"
>
> So from that last line I am pretty sure that the "62" in
>
> $w cmd plmaptex {} "ss/ss64ne_General_Text" 1.0 0.0 0.5
> "Caffyns\nHeanton\nDown" $minx $maxx $miny $maxy 62
>
> in examples/tcl/x19.tcl is the cause of the above matrix operator warning on Linux.
>
> That warning message comes from line 382 of bindings/tcl/tclMatrix.c.
> I notice that for all other error conditions that are handled with Tcl_AppendResult,
> the returned value is TCL_ERROR, but in this particular case the returned value is
> NULL.  Is that difference in pattern significant?  In other words, if you changed that
> NULL to TCL_ERROR would that solve the segfault on Cygwin?
>
> In other words do we have two bugs here; one where some misuse of matrix is
> causing the
>
> No matrix operator named "62"
>
> warning message, and then a second bug in the way that issue is handled?
>
> Anyhow, I hope these speculations lead you to a definitive fix for both bugs if it
> turns out you agree with me that there are actually two bugs to deal with here, the
> NULL return value that likely should be changed to TCL_ERROR to get rid of the
> segfault on Cygwin, and also the actual condition that causes the above matrix
> operator message to be emitted.
>
Well, I did notice that a lot of PostScript files were created for the Tcl target - glad you found the real culprit example.

Tcl will complain and produce a runtime error when something is not right - in this case a non-existent matrix will cause it to abort immediately with a useful error message. A segfault is not part of the usual termination procedure so something below the level of the script may be wrong too. I will have a closer look at example x19 and the underlying API.

Regards,

Arjen

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