From 9edcb0060f02acc3c603cc1cd860d9f28c5898b7 Mon Sep 17 00:00:00 2001
From: TAKAI Kousuke <62541129+t-a-k@users.noreply.github.com>
Date: Thu, 20 Nov 2025 01:01:26 +0900
Subject: [PATCH] grok_bin_oct_hex: Remove unnecessary initializer for `factor`

The initial value of `factor` before this change, `shift << bytes_so_far`,
is effectively not used, as it will be only used in multiplication with
zero (initial value of `value_nv`) on first overflow.
Moreover, this original initializer expression might cause undefined
behaviour as `bytes_so_far` (= s - s0) might become too large for shift
amount if the string had many leading zeros.

t/op/oct.t: Added tests to ensure this change won't change the behaviour.
---
 numeric.c  | 5 +----
 t/op/oct.t | 7 ++++++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/numeric.c b/numeric.c
index 4ed6a1409bda..ea855912dcf1 100644
--- a/numeric.c
+++ b/numeric.c
@@ -487,12 +487,9 @@ Perl_grok_bin_oct_hex(pTHX_ const char * const start,
           break;
     }
 
-    /* How many real digits have been processed */
-    STRLEN bytes_so_far = s - s0;
-
     /* In overflows, this keeps track of how much to multiply the overflowed NV
      * by as we continue to parse the remaining digits */
-    NV factor = shift << bytes_so_far;
+    NV factor = 0.0;
 
     bool overflowed = FALSE;
     NV value_nv = 0;
diff --git a/t/op/oct.t b/t/op/oct.t
index 6d16ed0ae514..d84d90ab7c36 100644
--- a/t/op/oct.t
+++ b/t/op/oct.t
@@ -5,8 +5,9 @@
 chdir 't' if -d 't';
 require './test.pl';
 use strict;
+no warnings 'overflow';
 
-plan(tests => 79);
+plan(tests => 81);
 
 foreach(['0b1_0101', 0b101_01],
 	['0b10_101', 0_2_5],
@@ -58,6 +59,8 @@ foreach(['0b1_0101', 0b101_01],
         # Additional syntax for octals
         ["0o7_654_321", 2054353],
         ["O4567", 0o4_567],
+        # Overflow approximation
+        ["52" x 32, 4184734490257787175890526282138444277401570296309356341930],
        ) {
     my ($string, $value) = @$_;
     my $result = oct $string;
@@ -95,6 +98,8 @@ foreach(['01_234', 0b_1001000110100],
 	# Allow uppercase base markers (#76296)
 	["0XCAFE",   0xCAFE],
 	["XCAFE",    0xCAFE],
+        # Overflow approximation
+        ["5" x 48, 2092367245128893587945263141069222138700785148154678170965],
        ) {
     my ($string, $value) = @$_;
     my $result = hex $string;