From bcb89c75ece71869c99032e078e0ec4fe12b2645 Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Fri, 16 Jul 2021 14:49:25 +0200
Subject: [PATCH] Fix #78238: BCMath returns "-0"

There is no negative zero in the decimal system, so we must suppress
the sign.

Closes GH-7250.
---
 NEWS                               |  3 +++
 ext/bcmath/libbcmath/src/bcmath.h  |  2 ++
 ext/bcmath/libbcmath/src/num2str.c |  2 +-
 ext/bcmath/libbcmath/src/zero.c    | 10 ++++++++--
 ext/bcmath/tests/bug78238.phpt     | 18 ++++++++++++++++++
 5 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100644 ext/bcmath/tests/bug78238.phpt

diff --git a/NEWS b/NEWS
index 7d049b33c30..a60fdf79234 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,9 @@ PHP                                                                        NEWS
 - Core:
   . Fixed bug #72595 (php_output_handler_append illegal write access). (cmb)
 
+- BCMath:
+  . Fixed bug #78238 (BCMath returns "-0"). (cmb)
+
 - CGI:
   . Fixed bug #80849 (HTTP Status header truncation). (cmb)
 
diff --git a/ext/bcmath/libbcmath/src/bcmath.h b/ext/bcmath/libbcmath/src/bcmath.h
index becba7ec3e2..74e9fbc7a99 100644
--- a/ext/bcmath/libbcmath/src/bcmath.h
+++ b/ext/bcmath/libbcmath/src/bcmath.h
@@ -120,6 +120,8 @@ _PROTOTYPE(int bc_compare, (bc_num n1, bc_num n2));
 
 _PROTOTYPE(char bc_is_zero, (bc_num num));
 
+_PROTOTYPE(char bc_is_zero_for_scale, (bc_num num, int scale));
+
 _PROTOTYPE(char bc_is_near_zero, (bc_num num, int scale));
 
 _PROTOTYPE(char bc_is_neg, (bc_num num));
diff --git a/ext/bcmath/libbcmath/src/num2str.c b/ext/bcmath/libbcmath/src/num2str.c
index 23988c0d6c5..546e87a22fd 100644
--- a/ext/bcmath/libbcmath/src/num2str.c
+++ b/ext/bcmath/libbcmath/src/num2str.c
@@ -50,7 +50,7 @@ zend_string
 	int  index, signch;
 
 	/* Allocate the string memory. */
-	signch = num->n_sign != PLUS;  /* Number of sign chars. */
+	signch = num->n_sign != PLUS && !bc_is_zero_for_scale(num, MIN(num->n_scale, scale));  /* Number of sign chars. */
 	if (scale > 0)
 		str = zend_string_alloc(num->n_len + scale + signch + 1, 0);
 	else
diff --git a/ext/bcmath/libbcmath/src/zero.c b/ext/bcmath/libbcmath/src/zero.c
index 28038201242..ba188d04369 100644
--- a/ext/bcmath/libbcmath/src/zero.c
+++ b/ext/bcmath/libbcmath/src/zero.c
@@ -40,7 +40,7 @@
 /* In some places we need to check if the number NUM is zero. */
 
 char
-bc_is_zero (bc_num num)
+bc_is_zero_for_scale (bc_num num, int scale)
 {
   int  count;
   char *nptr;
@@ -49,7 +49,7 @@ bc_is_zero (bc_num num)
   if (num == BCG(_zero_)) return TRUE;
 
   /* Initialize */
-  count = num->n_len + num->n_scale;
+  count = num->n_len + scale;
   nptr = num->n_value;
 
   /* The check */
@@ -60,3 +60,9 @@ bc_is_zero (bc_num num)
   else
     return TRUE;
 }
+
+char
+bc_is_zero (bc_num num)
+{
+  return bc_is_zero_for_scale(num, num->n_scale);
+}
diff --git a/ext/bcmath/tests/bug78238.phpt b/ext/bcmath/tests/bug78238.phpt
new file mode 100644
index 00000000000..6752f45a7db
--- /dev/null
+++ b/ext/bcmath/tests/bug78238.phpt
@@ -0,0 +1,18 @@
+--TEST--
+Bug #78238 (BCMath returns "-0")
+--SKIPIF--
+<?php
+if (!extension_loaded('bcmath')) die("sikp bcmath extension not available");
+?>
+--FILE--
+<?php
+var_dump(bcadd("0", "-0.1"));
+
+$a = bcmul("0.9", "-0.1", 1);
+$b = bcmul("0.90", "-0.1", 1);
+var_dump($a, $b);
+?>
+--EXPECT--
+string(1) "0"
+string(3) "0.0"
+string(3) "0.0"