Correctly compare 0 and -0 (#17051)

Fixes #17049
Closes #17051

Author: SakiTakamachi

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.4.3
 
+- BcMath:
+  . Fixed bug GH-17049 (Correctly compare 0 and -0). (Saki Takamachi)
+
 - Iconv:
   . Fixed bug GH-17047 (UAF on iconv filter failure). (nielsdos)
 
@@ -12,7 +15,7 @@ PHP                                                                        NEWS
 05 Dec 2024, PHP 8.4.2
 
 - BcMath:
-  . Fixed bug GH-16978 (Avoid unnecessary padding with leading zeros)
+  . Fixed bug GH-16978 (Avoid unnecessary padding with leading zeros).
     (Saki Takamachi)
 
 - COM:

ext/bcmath/libbcmath/src/compare.c

@@ -45,6 +45,18 @@ bcmath_compare_result _bc_do_compare(bc_num n1, bc_num n2, size_t scale, bool us
 
 	/* First, compare signs. */
 	if (use_sign && n1->n_sign != n2->n_sign) {
+		/*
+		 * scale and n->n_scale differ only in Number objects.
+		 * This happens when explicitly specify the scale in a Number method.
+		 */
+		if ((n1->n_scale > scale || n2->n_scale > scale) &&
+			n1->n_len == 1 && n2->n_len == 1 &&
+			n1->n_value[0] == 0 && n2->n_value[0] == 0 &&
+			bc_is_zero_for_scale(n1, scale) && bc_is_zero_for_scale(n2, scale)
+		) {
+			/* e.g. 0.00 <=> -0.00 */
+			return BCMATH_EQUAL;
+		}
 		if (n1->n_sign == PLUS) {
 			/* Positive N1 > Negative N2 */
 			return BCMATH_LEFT_GREATER;

ext/bcmath/libbcmath/src/str2num.c

@@ -173,6 +173,15 @@ bool bc_str2num(bc_num *num, const char *str, const char *end, size_t scale, siz
 		if (str_scale > scale && !auto_scale) {
 			fractional_end -= str_scale - scale;
 			str_scale = scale;
+
+			/*
+			 * e.g. 123.0001 with scale 2 -> 123.00
+			 * So, remove the trailing 0 again.
+			 */
+			if (str_scale > 0) {
+				const char *fractional_new_end = bc_skip_zero_reverse(fractional_end, fractional_ptr);
+				str_scale -= fractional_new_end - fractional_end;
+			}
 		}
 	} else {
 		if (full_scale) {

ext/bcmath/tests/bccomp_variation002.phpt

@@ -13,6 +13,7 @@ echo bccomp("-2.29", "2.3", "2") . "\n";
 echo bccomp("2.29", "-2.3", "2") . "\n";
 echo bccomp("-2.29", "-2.3", "1") . "\n";
 echo bccomp("-2.29", "0", "1") . "\n";
+echo bccomp("0.001", "-0.001", "1") . "\n";
 ?>
 --EXPECT--
 0
@@ -22,3 +23,4 @@ echo bccomp("-2.29", "0", "1") . "\n";
 1
 1
 -1
+0

ext/bcmath/tests/number/methods/compare_near_zero.phpt

@@ -0,0 +1,71 @@
+--TEST--
+BcMath\Number compare() with scale
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+
+$values1 = [
+    new BcMath\Number('0.001'),
+    new BcMath\Number('-0.001'),
+];
+
+$values2 = [
+    0,
+    -0,
+    '0.0011',
+    '-0.0011',
+];
+
+$value1 = new BcMath\Number('0.001');
+
+$scales = [0, 2, 3, 4];
+
+foreach ($scales as $scale) {
+    echo "========== scale is {$scale} ==========\n";
+    foreach ($values1 as $value1) {
+        foreach ($values2 as $value2) {
+            $output = str_pad("{$value1} <=> {$value2}: ", 20, ' ', STR_PAD_LEFT);
+            $output .= str_pad((string) $value1->compare($value2, $scale), 2, ' ', STR_PAD_LEFT);
+            echo "{$output}\n";
+        }
+    }
+}
+?>
+--EXPECT--
+========== scale is 0 ==========
+       0.001 <=> 0:  0
+       0.001 <=> 0:  0
+  0.001 <=> 0.0011:  0
+ 0.001 <=> -0.0011:  0
+      -0.001 <=> 0:  0
+      -0.001 <=> 0:  0
+ -0.001 <=> 0.0011:  0
+-0.001 <=> -0.0011:  0
+========== scale is 2 ==========
+       0.001 <=> 0:  0
+       0.001 <=> 0:  0
+  0.001 <=> 0.0011:  0
+ 0.001 <=> -0.0011:  0
+      -0.001 <=> 0:  0
+      -0.001 <=> 0:  0
+ -0.001 <=> 0.0011:  0
+-0.001 <=> -0.0011:  0
+========== scale is 3 ==========
+       0.001 <=> 0:  1
+       0.001 <=> 0:  1
+  0.001 <=> 0.0011:  0
+ 0.001 <=> -0.0011:  1
+      -0.001 <=> 0: -1
+      -0.001 <=> 0: -1
+ -0.001 <=> 0.0011: -1
+-0.001 <=> -0.0011:  0
+========== scale is 4 ==========
+       0.001 <=> 0:  1
+       0.001 <=> 0:  1
+  0.001 <=> 0.0011: -1
+ 0.001 <=> -0.0011:  1
+      -0.001 <=> 0: -1
+      -0.001 <=> 0: -1
+ -0.001 <=> 0.0011: -1
+-0.001 <=> -0.0011:  1