Blank line macro (.blm) evil with `groff -ms'

[Wirawan Purwanto]

Hi,

I would like to report a problem with groff compilation when the
"blank line macro" request (.blm) is used. It seems that there is some
sensitivity to whether there is a blank line just before or after the
.blm line (either with or without an argument). I attach also a
testcase for you to try.

To reproduce the problem, invoke:

 $ groff -ms groff-1.18-blm-bug.groff > /dev/null

There will be warnings like this:

 groff-1.18-blm-bug.groff:33: warning [p 1, 1.0i]: can't break line

(line number may vary; the last time I tried it became 61). If we use
`-ww' command-line option also, then it's becoming more verbose:

 groff-1.18-blm-bug.groff:38: warning: number register `0:LL' not defined
 groff-1.18-blm-bug.groff:38: warning: number register `0:ri' not defined
 groff-1.18-blm-bug.groff:38: warning: number register `0:pri' not defined
 ...
 groff-1.18-blm-bug.groff:41: warning [p 1, 1.0i]: can't break line
 groff-1.18-blm-bug.groff:41: warning [p 1, 1.0i]: can't break line

If we use `-b' option, the problem is blamed on s.tmac:

 /usr/share/groff/1.18.1/tmac/s.tmac:1095: backtrace: macro address@hidden'
 /usr/share/groff/1.18.1/tmac/s.tmac:172: backtrace: macro `TL'
 groff-1.18-blm-bug.groff:38: warning: number register `0:LL' not defined
 /usr/share/groff/1.18.1/tmac/s.tmac:1095: backtrace: macro address@hidden'
 /usr/share/groff/1.18.1/tmac/s.tmac:172: backtrace: macro `TL'
 groff-1.18-blm-bug.groff:38: warning: number register `0:ri' not defined
 /usr/share/groff/1.18.1/tmac/s.tmac:1095: backtrace: macro address@hidden'
 /usr/share/groff/1.18.1/tmac/s.tmac:172: backtrace: macro `TL'
 groff-1.18-blm-bug.groff:38: warning: number register `0:pri' not defined
 ...

If you examine the resulting postscript file, the letters became very
tiny (virtually illegible). If we add a blank line JUST above the
`.blm blankline' text line,
all the problems above disappear, and the postscript result is OK.

What's more bizzare is that you can alleviate the problem by removing
the first `.br' line in the testcase. But that .br was needed in my
actual script. So it looks like `.blm' is an evil macro in certain
instances. Why is this?

Let me know if you need more detail of the problem. I am using Ubuntu
Linux 7.04 and GROFF version 1.18.1 . The same problem appears under
Fedora Core 6 + GROFF 1.18.1 combination.

--
Wirawan Purwanto
College of William and Mary
Physics Department
Williamsburg, VA 23187

groff-1.18-blm-bug.groff
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