From d434dd3ec16dc1202626e9868f177203e2a86da5 Mon Sep 17 00:00:00 2001
From: Karl Williamson <khw@cpan.org>
Date: Thu, 21 Mar 2019 09:35:49 -0600
Subject: [PATCH] PATCH: [perl #133880] assertion failure
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This was caused by attempting to continue parsing after an error is
found, and later assuming that what came before was valid.  The fix is
to put in something valid that's usable until the parse eventually dies
from what caused this, or some other error.

Signed-off-by: Ported to 5.28.1 from
ef65a74af186beb93566cf827c5f543f4aa14645.
Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 t/op/tr.t | 8 +++++++-
 toke.c    | 8 ++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/t/op/tr.t b/t/op/tr.t
index 0f74936..47d603d 100644
--- a/t/op/tr.t
+++ b/t/op/tr.t
@@ -13,7 +13,7 @@ BEGIN {
 
 use utf8;
 
-plan tests => 300;
+plan tests => 301;
 
 # Test this first before we extend the stack with other operations.
 # This caused an asan failure due to a bad write past the end of the stack.
@@ -1137,6 +1137,12 @@ for ("", nullrocow) {
     [\x{E5CD}-\x{E5DF}\x{EA80}-\x{EAFA}\x{EB0E}-\x{EB8E}\x{EAFB}-\x{EB0D}\x{E5B5}-\x{E5CC}];
 
     is $x, "\x{E5CE}", '[perl #130656]';
+
+}
+
+{
+    fresh_perl_like('y/\x{a00}0-\N{}//', qr/Unknown charname/, { },
+                    'RT #133880 illegal \N{}');
 }
 
 1;
diff --git a/toke.c b/toke.c
index 3164df5..4747ef5 100644
--- a/toke.c
+++ b/toke.c
@@ -3770,8 +3770,12 @@ S_scan_const(pTHX_ char *start)
 		    }
 		}
 		else /* Here is \N{NAME} but not \N{U+...}. */
-                     if ((res = get_and_check_backslash_N_name(s, e)))
-                {
+                     if (! (res = get_and_check_backslash_N_name(s, e)))
+                {   /* Failed.  We should die eventually, but for now use a NUL
+                       to keep parsing */
+                    *d++ = '\0';
+                }
+                else {  /* Successfully evaluated the name */
                     STRLEN len;
                     const char *str = SvPV_const(res, len);
                     if (PL_lex_inpat) {
-- 
2.20.1