Safely handle null pointers in Util.UnsafeSpanFromPointer

Author: YoshiRulz

src/BizHawk.Common/Util.cs

@@ -287,24 +287,24 @@ static bool TryWaitForFileToVanish(string path)
 		}
 
 		/// <summary>creates span over <paramref name="length"/> octets starting at <paramref name="ptr"/></summary>
+		/// <remarks>returns empty span if <paramref name="ptr"/> is the null pointer (<see cref="IntPtr.Zero"/>)</remarks>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static unsafe Span<byte> UnsafeSpanFromPointer(IntPtr ptr, int length)
-		{
-			return new(pointer: ptr.ToPointer(), length: length);
-		}
+			=> ptr == IntPtr.Zero ? [ ] : new(pointer: ptr.ToPointer(), length: length);
 
 #if false // unused
 		/// <summary>
 		/// creates span over <paramref name="count"/><c> * sizeof(</c><typeparamref name="T"/><c>)</c> octets
 		/// starting at <paramref name="ptr"/>
 		/// </summary>
-		/// <remarks>uses native endianness and <paramref name="ptr"/> must be aligned (else UB)</remarks>
+		/// <remarks>
+		/// uses native endianness and <paramref name="ptr"/> must be aligned (else UB);
+		/// returns empty span if <paramref name="ptr"/> is the null pointer (<see cref="IntPtr.Zero"/>)
+		/// </remarks>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static unsafe Span<T> UnsafeSpanFromPointerAligned<T>(IntPtr ptr, int count)
 			where T : unmanaged
-		{
-			return new(pointer: ptr.ToPointer(), length: count * sizeof(T));
-		}
+			=> ptr == IntPtr.Zero ? [ ] : new(pointer: ptr.ToPointer(), length: count * sizeof(T));
 #endif
 
 		public static void WriteByteBuffer(this BinaryWriter bw, byte[]? data)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/3DS/Encore.IMemoryDomains.cs

@@ -72,10 +72,9 @@ public EncoreMMU(IntPtr context)
 			}
 
 			private Span<byte> GetPage(uint addr)
-			{
-				var pagePointer = _core.Encore_GetPagePointer(_context, addr);
-				return pagePointer == IntPtr.Zero ? [ ] : Util.UnsafeSpanFromPointer(pagePointer, (int)(ENCORE_PAGE_SIZE - (addr & ENCORE_PAGE_MASK)));
-			}
+				=> Util.UnsafeSpanFromPointer(
+					ptr: _core.Encore_GetPagePointer(_context, addr: addr),
+					length: (int) (ENCORE_PAGE_SIZE - (addr & ENCORE_PAGE_MASK)));
 
 			public override byte PeekByte(long addr)
 			{