When .Sm is called without an argument, groff toggles the spacing mode,

so let us do the same for compatibility.  Using this feature is of
course not recommended except in manual page obfuscation contests.

1 files changed, 8 insertions, 3 deletions

diff --git a/mdoc_man.c b/mdoc_man.c
index 8e81a1fb..59de74ab 100644
--- a/mdoc_man.c
+++ b/mdoc_man.c
@@ -1565,11 +1565,16 @@ static int
 pre_sm(DECL_ARGS)
 {
 
-	assert(n->child && MDOC_TEXT == n->child->type);
-	if (0 == strcmp("on", n->child->string))
-		outflags |= MMAN_Sm | MMAN_spc;
+	if (NULL == n->child)
+		outflags ^= MMAN_Sm;
+	else if (0 == strcmp("on", n->child->string))
+		outflags |= MMAN_Sm;
 	else
 		outflags &= ~MMAN_Sm;
+
+	if (MMAN_Sm & outflags)
+		outflags |= MMAN_spc;
+
 	return(0);
 }