From ef036090d986beab2690fa400084411dbefad57e Mon Sep 17 00:00:00 2001
From: Saki Takamachi <saki@php.net>
Date: Fri, 27 Dec 2024 21:36:26 +0900
Subject: [PATCH] Fixed GH-17275: Fixed the calculation logic of dividend scale
 (#17279)

Fixes #17275
Closes #17279
---
 NEWS                           |  2 ++
 ext/bcmath/libbcmath/src/div.c | 14 ++++++++++----
 ext/bcmath/tests/gh17275.phpt  | 14 ++++++++++++++
 3 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 ext/bcmath/tests/gh17275.phpt

diff --git a/NEWS b/NEWS
index 898dda52a4d..d2222b5123c 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,8 @@ PHP                                                                        NEWS
     (Saki Takamachi)
   . Fixed bug GH-17064 (Correctly round rounding mode with zero edge case).
     (Saki Takamachi)
+  . Fixed bug GH-17275 (Fixed the calculation logic of dividend scale).
+    (Saki Takamachi)
 
 - Core:
   . Fixed bug OSS-Fuzz #382922236 (Duplicate dynamic properties in hooked object
diff --git a/ext/bcmath/libbcmath/src/div.c b/ext/bcmath/libbcmath/src/div.c
index e9377fcfc42..ce9ae1e1dd7 100644
--- a/ext/bcmath/libbcmath/src/div.c
+++ b/ext/bcmath/libbcmath/src/div.c
@@ -427,6 +427,9 @@ bool bc_divide(bc_num numerator, bc_num divisor, bc_num *quot, size_t scale)
 		return true;
 	}
 
+	/* Length of numerator data that can be read */
+	size_t numerator_readable_len = numeratorend - numeratorptr + 1;
+
 	/* set scale to numerator */
 	if (numerator_scale > scale) {
 		size_t scale_diff = numerator_scale - scale;
@@ -434,7 +437,13 @@ bool bc_divide(bc_num numerator, bc_num divisor, bc_num *quot, size_t scale)
 			numerator_bottom_extension -= scale_diff;
 		} else {
 			numerator_bottom_extension = 0;
-			numeratorend -= scale_diff > numerator_top_extension ? scale_diff - numerator_top_extension : 0;
+			if (EXPECTED(numerator_readable_len > scale_diff)) {
+				numerator_readable_len -= scale_diff;
+				numeratorend -= scale_diff;
+			} else {
+				numerator_readable_len = 0;
+				numeratorend = numeratorptr;
+			}
 		}
 		numerator_top_extension = MIN(numerator_top_extension, scale);
 	} else {
@@ -442,9 +451,6 @@ bool bc_divide(bc_num numerator, bc_num divisor, bc_num *quot, size_t scale)
 	}
 	numerator_scale = scale;
 
-	/* Length of numerator data that can be read */
-	size_t numerator_readable_len = numeratorend - numeratorptr + 1;
-
 	if (divisor_len > numerator_readable_len + numerator_bottom_extension) {
 		*quot = bc_copy_num(BCG(_zero_));
 		return true;
diff --git a/ext/bcmath/tests/gh17275.phpt b/ext/bcmath/tests/gh17275.phpt
new file mode 100644
index 00000000000..c5be97bdaa8
--- /dev/null
+++ b/ext/bcmath/tests/gh17275.phpt
@@ -0,0 +1,14 @@
+--TEST--
+GH-17275 Incorrect result of bcdiv function
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+var_dump(
+    bcdiv('0.03772321', '9650.0', 8),
+    bcdiv('0.03772321', '9650.0', 9),
+);
+?>
+--EXPECT--
+string(10) "0.00000390"
+string(11) "0.000003909"