$ ksh -c 'trap "" CONT; trap'
trap -- CONT
That is not "suitable for re-entry into the shell". Empty words must be
quoted, or they disappear. Expected output:
trap -- '' CONT
Patch below. OK?
- M.
Index: misc.c
===================================================================
RCS file: /cvs/src/bin/ksh/misc.c,v
retrieving revision 1.70
diff -u -p -r1.70 misc.c
--- misc.c 9 Apr 2018 17:53:36 -0000 1.70
+++ misc.c 14 Apr 2018 22:44:39 -0000
@@ -966,6 +966,12 @@ print_value_quoted(const char *s)
const char *p;
int inquote = 0;
+ /* Check for empty */
+ if (!*p) {
+ shprintf("''");
+ return;
+ }
+
/* Test if any quotes are needed */
for (p = s; *p; p++)
if (ctype(*p, C_QUOTE))
