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

[C.M. Connelly]

"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
#3  0x1002ca3c in doaddto () at mf1.c:9773
#4  0x1002e4cc in dostatement () at mf2.c:707
#5  0x1002f4a8 in scanprimary () at mf2.c:1169
#6  0x1002ff9c in scansecondary () at mf2.c:1610
#7  0x100300b8 in scantertiary () at mf2.c:1649
#8  0x1003021c in scanexpression () at mf2.c:1695
#9  0x1002e27c in dostatement () at mf2.c:612
#10 0x1002e670 in maincontrol () at mf2.c:781
#11 0x10004d68 in mainbody () at mfini.c:1290
#12 0x10033de8 in main (ac=109, av=0xf6a61a24) at mfnowin.c:247
#13 0xfe92cc8 in __libc_start_main () from /lib/libc.so.6

Beyond that, I'm stumped.

   CMC

+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
 Behind the counter a boy with a shaven head stared vacantly into space, 
 a dozen spikes of microsoft protruding from the socket behind his ear.
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   C.M. Connelly               c@eskimo.com                   SHC, DS
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