This patch comes from in-house and has been submitted upstream:

--- groff-1.22.2/src/roff/troff/env.cpp.org 2013-02-07 21:06:06.000000000 +0900

+++ groff-1.22.2/src/roff/troff/env.cpp 2015-01-14 10:23:07.817142586 +0900

@@ -2110,6 +2110,9 @@

}

distribute_space(pre, bp->nspaces, extra_space_width);

hunits output_width = bp->width + extra_space_width;

+ if (output_width <= 0)

+ return;

+

input_line_start -= output_width;

if (bp->hyphenated)

hyphen_line_count++;