Bug#83146: [tex-k] Bug#83146: MF fatal error

[Julian Gilbey]

On Wed, Jan 24, 2001 at 06:50:37PM -0800, C.M. Connelly wrote:
> "JG" => Julian Gilbey <J.D.Gilbey@qmw.ac.uk>
> 
>     JG> Wow!  I got a MetaFont "This can't happen (m)" error.  Here's
>     JG> how I did it.
>     JG> 
>     JG> mf '\mode:=ljfzzz; mag:=1+0/1200; nonstopmode; input xslhz20'
>     JG> 
>     JG> Now ljfzzz is in the standard modes.mf:
> 
> 
> It seems to have something to do with the printer resolution -- if
> you try the same command line with the ljfour or ljfzzzfr modes,
> it works just fine.
> 
> The sanity-checking code that reports the error is in
> teTeX-src/texk/web2c/mf.web, line 6907 (section 311 in the typeset
> documentation (page 128)):
> 
>    begin if (xx3<xx0)or(yy3<yy0) then confusion("m");
> 
> The problem is with yy0 and yy3 -- when the error occurs, 
> yy0=156729345 and yy3=156729344.  A backtrace gets you
> 
> Breakpoint 1, zconfusion (s=109) at mf0.c:1120
> 1120	  normalizeselector () ;
> (gdb) bt
> #0  zconfusion (s=109) at mf0.c:1120
> #1  0x1000f864 in zmakemoves (xx0=-157273438, xx1=-156886492, xx2=-156499546, 
>     xx3=-156112599, yy0=156729345, yy1=156729345, yy2=156729345, 
>     yy3=156729344, xicorr=1 '\001', etacorr=0 '\000') at mf0.c:6374
> #2  0x10016eac in zfillspec (h=4325) at mf0.c:9657

Yup, I'd got that far too.  But now it needs some serious debugging to
figure out how this could have ever come to be.  "This can't happen"
should mean just that!

   Julian

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         Julian Gilbey, Dept of Maths, Queen Mary, Univ. of London
       Debian GNU/Linux Developer,  see http://people.debian.org/~jdg
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