From f29d2c50d858a48eef4ce806fd5c73d38a04b1f2 Mon Sep 17 00:00:00 2001
From: Lukas Mai <lukasmai.403@gmail.com>
Date: Sun, 17 Aug 2025 07:32:15 +0200
Subject: [PATCH] don't blame $x if reftype($x)/refaddr($x) is undef

When the "Use of uninitialized value" warning tries to find the source
of the problem, it skips over builtin::reftype/builtin::refaddr
operations and blames their arguments:

    $ perl -wE 'my $x = 42; $_ = reftype($x) eq ""'
    Use of uninitialized value $x in string eq at -e line 1.
    $ perl -wE 'my $x = 42; $_ = refaddr($x) eq ""'
    Use of uninitialized value $x in string eq at -e line 1.

This is wrong because $x is clearly defined.

This patch teaches S_find_uninit_var that reftype/refaddr can return
undef even if their arguments are perfectly defined.

Fixes #19273.
---
 sv.c                   | 2 ++
 t/lib/warnings/9uninit | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/sv.c b/sv.c
index b4d2fd705af4..2c337501bc6c 100644
--- a/sv.c
+++ b/sv.c
@@ -17532,6 +17532,8 @@ S_find_uninit_var(pTHX_ const OP *const obase, const SV *const uninit_sv,
     case OP_SYSOPEN:
     case OP_SYSSEEK:
     case OP_SPLICE: /* scalar splice(@x, $i, 0) ==> undef */
+    case OP_REFADDR:
+    case OP_REFTYPE:
         match = 1;
         goto do_op;
 
diff --git a/t/lib/warnings/9uninit b/t/lib/warnings/9uninit
index 38d49942a670..4ca08684a020 100644
--- a/t/lib/warnings/9uninit
+++ b/t/lib/warnings/9uninit
@@ -2303,3 +2303,12 @@ Use of uninitialized value shift(@ARGV) in lc at - line 26.
 Use of uninitialized value shift() in lc at - line 27.
 Use of uninitialized value pop(@ARGV) in lc at - line 28.
 Use of uninitialized value pop() in lc at - line 29.
+########
+# GH #19273
+use warnings 'uninitialized';
+my $x = 'fine';
+$_ = builtin::refaddr($x) == 1;
+$_ = builtin::reftype($x) eq '';
+EXPECT
+Use of uninitialized value in numeric eq (==) at - line 4.
+Use of uninitialized value in string eq at - line 5.