12364 mdb trips assertion related to autowrap

@@ -23,11 +23,11 @@
  * Use is subject to license terms.
  */
 
 /*
  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
- * Copyright 2015 Joyent, Inc.
+ * Copyright 2020 Joyent, Inc.
  * Copyright (c) 2014 Nexenta Systems, Inc. All rights reserved.
  */
 
 #include <mdb/mdb_modapi.h>
 #include <mdb/mdb_target.h>

@@ -929,10 +929,34 @@
 
         return (0);
 }
 
 /*
+ * We want to print an escaped char as e.g. '\0'. We don't use mdb_fmt_print()
+ * as it won't get auto-wrap right here (although even now, we don't include any
+ * trailing comma).
+ */
+static int
+print_char_val(mdb_tgt_addr_t addr, printarg_t *pap)
+{
+        char cval;
+        char *s;
+
+        if (mdb_tgt_aread(pap->pa_tgt, pap->pa_as, &cval, 1, addr) != 1)
+                return (1);
+
+        if (mdb.m_flags & MDB_FL_ADB)
+                s = strchr2adb(&cval, 1);
+        else
+                s = strchr2esc(&cval, 1);
+
+        mdb_printf("'%s'", s);
+        strfree(s);
+        return (0);
+}
+
+/*
  * Print out a character or integer value.  We use some simple heuristics,
  * described below, to determine the appropriate radix to use for output.
  */
 static int
 print_int_val(const char *type, ctf_encoding_t *ep, ulong_t off,

@@ -969,18 +993,12 @@
          */
         size = ep->cte_bits / NBBY;
         if (size > 8 || (ep->cte_bits % NBBY) != 0 || (size & (size - 1)) != 0)
                 return (print_bitfield(off, pap, ep));
 
-        if (IS_CHAR(*ep)) {
-                mdb_printf("'");
-                if (mdb_fmt_print(pap->pa_tgt, pap->pa_as,
-                    addr, 1, 'C') == addr)
-                        return (1);
-                mdb_printf("'");
-                return (0);
-        }
+        if (IS_CHAR(*ep))
+                return (print_char_val(addr, pap));
 
         if (mdb_tgt_aread(pap->pa_tgt, pap->pa_as, &u.i8, size, addr) != size) {
                 mdb_warn("failed to read %lu bytes at %llx",
                     (ulong_t)size, addr);
                 return (1);