From 5695970362d363d0d4dcf2b5e708053dafad6a42 Mon Sep 17 00:00:00 2001
From: Lukas Mai <lukasmai.403@gmail.com>
Date: Wed, 30 Jul 2025 23:09:54 +0200
Subject: [PATCH] class.c: gracefully handle reader/writer after 'strict' error

Fixes #23511.
---
 MANIFEST          |  1 +
 class.c           |  6 ++++--
 t/class/gh23511.t | 23 +++++++++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 t/class/gh23511.t

diff --git a/MANIFEST b/MANIFEST
index 2e0e256fe4b4..ad3ef0eddff5 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -6002,6 +6002,7 @@ t/class/construct.t			See if class constructors work
 t/class/destruct.t			See if class destruction works
 t/class/field.t				See if class field declarations work
 t/class/gh22169.t			Test defining a class that previously failed to define
+t/class/gh23511.t			Test defining a reader after a strict 'vars' violation
 t/class/inherit.t			See if class inheritance works
 t/class/method.t			See if class method declarations work
 t/class/phasers.t			See if class phaser blocks work
diff --git a/class.c b/class.c
index d6d801928d0b..a91656d46916 100644
--- a/class.c
+++ b/class.c
@@ -1140,7 +1140,8 @@ apply_field_attribute_reader(pTHX_ PADNAME *pn, SV *value)
     OP *nameop = newSVOP(OP_CONST, 0, value);
 
     CV *cv = newATTRSUB(floor_ix, nameop, NULL, NULL, ops);
-    CvIsMETHOD_on(cv);
+    if (cv)
+        CvIsMETHOD_on(cv);
 }
 
 /* If '@_' is called "snail", then elements of it can be called "slugs"; i.e.
@@ -1238,7 +1239,8 @@ apply_field_attribute_writer(pTHX_ PADNAME *pn, SV *value)
     OP *nameop = newSVOP(OP_CONST, 0, value);
 
     CV *cv = newATTRSUB(floor_ix, nameop, NULL, NULL, ops);
-    CvIsMETHOD_on(cv);
+    if (cv)
+        CvIsMETHOD_on(cv);
 }
 
 static struct {
diff --git a/t/class/gh23511.t b/t/class/gh23511.t
new file mode 100644
index 000000000000..ae6626900385
--- /dev/null
+++ b/t/class/gh23511.t
@@ -0,0 +1,23 @@
+#!./perl
+
+BEGIN {
+    chdir 't' if -d 't';
+    require './test.pl';
+    set_up_inc('../lib');
+}
+
+use v5.36;
+use feature 'class';
+no warnings 'experimental::class';
+
+# this used to segfault: GH #23511
+eval <<'CLASS';
+class MyTest {
+    $id = 6;
+    field $f1 :reader;
+    field $f2 :writer;
+}
+CLASS
+like $@, qr/^Global symbol "\$id" requires explicit package name /, "we get the expected 'undeclared variable' error";
+
+done_testing;