[bug #56555] I can make grops and grotty core dump with 5 bytes of input

[G. Branden Robinson]

Follow-up Comment #5, bug #56555 (project groff):

To clarify my earlier comment about "malformed input", there was nothing wrong
with the _syntax_ of the ditroff t command in the input file.

roff veterans know this, but a ditroff file requires some prologue (and
epilogue) to be well-formed.

My crasher document consisted solely of the characters "\!tr" (and a newline),
which used the "transparent line indicator" to pass the contents of the line
after the \! escape directly to groff's intermediate output format (which is a
pain to type out so I just say "ditroff").

"tr" means "typeset the letter r".

If we ask the groff frontend to typeset the letter "r", we get much more:


$ echo r | groff -Z
x T ps
x res 72000 1 1
x init
p1
x font 5 TR
f5
s10000
V12000
H72000
md
DFd
tr
n12000 0
x trailer
V792000
x stop


Careful inspection reveals a line exactly matching "tr".

One might be surprised to learn that the output for the supposedly-simpler
nroff/grotty devices is not any simpler.

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