Using an undefined string or macro will cause it to be defined as empty.

Observed by Werner Lemberg on Nov 14, 2011
and rotting on my TODO list ever since.

1 files changed, 37 insertions, 0 deletions

diff --git a/regress/roff/string/undef.out_ascii b/regress/roff/string/undef.out_ascii
new file mode 100644
index 00000000..6e7bd01f
--- /dev/null
+++ b/regress/roff/string/undef.out_ascii
@@ -0,0 +1,37 @@
+STRING-UNDEF(1)             General Commands Manual            STRING-UNDEF(1)
+
+
+
+NNAAMMEE
+       string-undef - expanding undefined strings
+
+DDEESSCCRRIIPPTTIIOONN
+   UUsseerr ddeeffiinneedd ssttrriinngg
+       The sting "mys" is undefined and remains undefined.
+
+       Its value is "", and now it is defined, and its value is still "".
+
+       After redefining it to "newval", it is of course still defined.
+
+       After removing the definition, it is now undefined.
+
+   UUsseerr ddeeffiinneedd mmaaccrroo
+       The macro "mym" is undefined.
+
+       It has no effect: But now it is defined.
+
+       After defining it as: neweffect it is of course still defined.
+
+       After removing the definition, it is now undefined.
+
+   RReennaammeedd mmaaccrroo
+       The standard .BR macro is defined, and it wwoorrkkss.
+
+       After renaming it, the new name is defined, and wwoorrkkss.
+
+   PPrreeddeeffiinneedd ssttrriinngg
+       A predefined string is defined and has the value "(R)".
+
+
+
+OpenBSD                          April 9, 2018                 STRING-UNDEF(1)