fix: il2cpp linux runtime SIGABRT crash with nanosockets (unity 2021.…

…3.15) (#1116)

* Update NanoSockets.cs

* Add modifications notice

* Minor restructure.

* Blank spacing

* Enable Mirage.Sockets.Udp unsafe code directive

* Fix v2 suggested by FakeByte and James

* Fix attempt v2

Assets/Mirage/Runtime/Sockets/Udp/Mirage.Sockets.Udp.asmdef

@@ -1,11 +1,12 @@
 {
     "name": "Mirage.Sockets.Udp",
+    "rootNamespace": "",
     "references": [
         "GUID:c0b2064c294eb174c9f3f7da398eb677"
     ],
     "includePlatforms": [],
     "excludePlatforms": [],
-    "allowUnsafeCode": false,
+    "allowUnsafeCode": true,
     "overrideReferences": false,
     "precompiledReferences": [],
     "autoReferenced": true,

Assets/Mirage/Runtime/Sockets/Udp/NanoEndPoint.cs

@@ -6,11 +6,10 @@ namespace Mirage.Sockets.Udp
 {
     public sealed class NanoEndPoint : IEndPoint, IEquatable<NanoEndPoint>
     {
-        public Address address;
+        public Address address = new Address();
 
         public NanoEndPoint(string host, ushort port)
         {
-            address = new Address();
             address.port = port;
             UDP.SetHostName(ref address, host);
         }

Assets/Mirage/Runtime/Sockets/Udp/NanoSockets/Scripts/NanoSockets.cs

@@ -1,7 +1,10 @@
 /*
  *  Lightweight UDP sockets abstraction for rapid implementation of message-oriented protocols
  *  Copyright (c) 2019 Stanislav Denisov
- *
+ *  
+ *  NanoSockets modifications made by Mirage Team
+ *  Copyright (c) 2022 Mirage Team and contributors.
+ *  
  *  Permission is hereby granted, free of charge, to any person obtaining a copy
  *  of this software and associated documentation files (the "Software"), to deal
  *  in the Software without restriction, including without limitation the rights
@@ -25,6 +28,7 @@
 using System.Runtime.InteropServices;
 using System.Security;
 using System.Text;
+using Mirage.SocketLayer;
 
 namespace NanoSockets
 {
@@ -85,13 +89,22 @@ public override int GetHashCode()
             return hash;
         }
 
-        public override string ToString()
+
+        public unsafe override string ToString()
         {
-            var ip = new StringBuilder(64);
-
-            NanoSockets.UDP.GetIP(ref this, ip, 64);
-
-            return string.Format("IP:{0} Port:{1}", ip, this.port);
+            // FIX: Unity IL2CPP SIGABRT in 2021.3.15 on Linux builds
+            // Problem: On Linux IL2CPP builds, it seems something with
+            // IL2CPP and StringBuilder causes SIGABRT to be emitted due to
+            // a bad free of a pointer: "free(): invalid pointer". Unity will then
+            // commit suicide.
+            // Solution: Allocate 64 bytes on the stack, tell NanoSockets to put the
+            // IP into that, then read as string in the return function. Tested and
+            // confirmed working on Manjaro x64 (Unity 2021.3.15).
+
+            // Attempt v2 (2022-12-09): Use unsafe pointer for the IP string.
+            var ptr = stackalloc char[64];
+            UDP.GetIP(ref this, (IntPtr)ptr, 64);
+            return $"IP: {new string(ptr)} Port: {this.Port}";
         }
 
         public static Address CreateFromIpPort(string ip, ushort port)

Assets/Mirage/Runtime/Sockets/Udp/UdpSocketFactory.cs

@@ -212,7 +212,6 @@ private static bool CheckNanosocketsSupport()
             || Application.isEditor;
 #endif
         }
-
     }
 
     public class EndPointWrapper : IEndPoint