Fix BigInteger bitwise operators on certain negative numbers (#109684)

Co-authored-by: Tanner Gooding <tagoo@outlook.com>
dotnet · Nov 13, 2024 · d3d0fce · d3d0fce
1 parent 4095634
commit d3d0fce
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Showing 2 changed files with 17 additions and 1 deletion.
diff --git a/src/libraries/System.Runtime.Numerics/src/System/Numerics/BigInteger.cs b/src/libraries/System.Runtime.Numerics/src/System/Numerics/BigInteger.cs
@@ -546,7 +546,7 @@ private BigInteger(Span<uint> value)
 
                 if ((length == 0) || ((int)value[length - 1] >= 0))
                 {
-                    // We ne need to preserve the sign bit
+                    // We need to preserve the sign bit
                     length++;
                 }
                 Debug.Assert((int)value[length - 1] < 0);

diff --git a/src/libraries/System.Runtime.Numerics/tests/BigInteger/op_and.cs b/src/libraries/System.Runtime.Numerics/tests/BigInteger/op_and.cs
@@ -120,6 +120,22 @@ public static void RunAndTests()
             }
         }
 
+        [Fact]
+        public void Issue109669()
+        {
+            // Operations on numbers whose result is of the form 0xFFFFFFFF 00000000 ... 00000000
+            // in two's complement.
+
+            Assert.Equal(-4294967296, new BigInteger(-4294967296) & new BigInteger(-1919810));
+            Assert.Equal(-4294967296, new BigInteger(-4042322161) & new BigInteger(-252645136));
+            Assert.Equal(-4294967296, new BigInteger(-8589934592) | new BigInteger(-21474836480));
+
+            BigInteger a = new BigInteger(MemoryMarshal.AsBytes([uint.MaxValue, 0u, 0u]), isBigEndian: true);
+            Assert.Equal(a, a & a);
+            Assert.Equal(a, a | a);
+            Assert.Equal(a, a ^ 0);
+        }
+
         [Fact]
         public static void RunAndTestsForSampleSet1()
         {