Mono 6.8.0 Release Notes

Release date: 15 Jan 2020


  • Various Bugfixes

In Depth



We continue to work on making our WebAssembly support better. Various sets of issues have been resolved in this release and general performance and feature work is happening as well.

Community improvements for AIX/PASE and Haiku

The ports for these systems received a bunch of improvements from community contributor Calvin Buckley (@NattyNarwhal).

Class Libraries

CoreFX integration

We continued to replace some of our classes with the implementation from CoreFX to improve performance and compatibility with .NET.

In this release we tightened up our networking with a few bug fixes.


Resolved Issues

  • 7377 [Mono.Debugger.Soft] Connections are not properly closed
  • 10641 New arm64_32 architecture (watchOS 5) [arm64_32] make “Debug Mode” work on Watch series 4 with –interpreter
  • 12421 Task calls SynchronizationContext.Post on cancelling
  • 12586 DataContractSerializer is not available
  • 12917 [Blazor] IL Linker not working correctly with IQueryable extensions
  • 14080 condition ‘ji’ not met, with ‘dynamic’ and multithreading
  • 14725 mono 5.20 hangs when called from native thread
  • 14772 Null Pointer Exception after debugger pauses and then continues
  • 15261 [iOS][Tests] There are a number of System.Numeric tests that fail on iOS 32b devices
  • 15262 [iOS][Tests] A number of linq tests fail on iOS 32b devices
  • 15263 [iOS][Tests] A number of tests from Microsoft.CSharp fail on iOS 32b devices.
  • 15307 [iOS][Tests] Several corelib tests crash on iOS32b devices.
  • 15308 [netcore] Make OverlappedTests.PackNegTest Pass
  • 15310 [netcore] Make OverlappedTests.UnPackTest Pass
  • 15646 MERP indefinitely hangs on application quit
  • 15687 [debugger] Update client thread frames after SetIP.
  • 15805 Mono.Net.Security.MonoTlsStream: Crash when stream appears to have already been disposed
  • 15931 1024 hard limit of open file descriptors
  • 15992 Mono crashes during precompiling dll in fullaot mode
  • 15994 Coverity: derefenrecing null in profiler (CID: 1307043) Skip degenerate qsort: num < 2, size == 0, base == 0
  • 15999 [mini] run regression tests with fullaot+llvm
  • 16010 typeof(object).GetMember(“”) does not return an empty array
  • 16024 Native crash in ves_icall_System_Net_Sockets_Socket_Connect_internal
  • 16032 IOException: Sharing violation on path …
  • 16046 [netcore] AOT with unresolved dependencies hits asserts
  • 16122 VS 16.2.0 regression: CopyToAsync from DeflateStream to GzipStream throws NotImplementedException
  • 16172 Interpreter stack size is too large
  • 16192 Embedded Mono hangs when using native threads
  • 16308 Change netcore package to be using release builds
  • 16310 LLVM: ““.AsSpan()[0] doesn’t throw IndexOutOfRangeException
  • 16319 [wasm] Timers do not fire when run inside WebWorkers.
  • 16369 Relocations in .text on arm
  • 16380 [netcore] Regession with AOTed System.Private.CoreLib
  • 16381 [llvm] Assertion: should not be reached at mini-llvm.c:7104
  • 16395 [Mobile] DateTime.Now returns incorrect local time for one hour after entering DST in 39 locales.
  • 16411 JitTests.Float fails on iOS devices in release mode on 2019-08
  • 16415 Timezone data not handled correctly on FreeBSD
  • 16460 System.IO.Path.GetFullPath(“\\.\pipe\pipename”): different results on Mono and .NET
  • 16486 FileSystemEventArgs.FullPath throws ArgumentNullException
  • 16605 make distclean fails after build w/ embedded zlib
  • 16616 [netcore] Vector.CopyTo w/ LLVM emits wrong exception
  • 16626 [WinForms] ControlBox property didn`t hide Close button and icon
  • 16689 [merp] missing data in crashing reporting json native frames
  • 16701 C# REPL Unusable on Mono 6 / Ubuntu 19
  • 16709 Disposing the FileSystemWatcher does not close associated file descriptors
  • 16712 SIGSEGV in mono_class_setup_vtable_general
  • 16742 Date.Time parse issue (year 1948) Avoid creating un-representable DateTime for transition point
  • 16759 Stream.ReadAsync continues on different thread
  • 16803 mono_gc_finalize_notify spinning after process exit
  • 16808 LLVM failed for String.GetHashCode
  • 16819 [coop][interp] mono_threads_enter_gc_safe_region Cannot transition thread 0x1952b000 from STATE_BLOCKING with DO_BLOCKING
  • 16824 Crash when debugging iOS application that throws on DispatchQueue
  • 16864 [arm64_32] fix remaining regression tests
  • 16876 [Wasm] Switch to PNSE FileWatcher & Exclude Tests
  • 16879 [Wasm] Determine if System.Net.Http.UnitTests Failures are Relevant
  • 16918 XmlSerializer Deserializing Property with same name as its enum type no longer works
  • 16943 LLVM: recursive calls have overhead in JIT mode
  • 16950 Starting in Mono 6.0 (2019-02), NotImplementedException prevents using StreamWriter with GZipStream for encodings that use a preamble
  • 16974 File.GetCreationTimeUtc() returns the time last modified, not time created
  • 17004 [merp] crash reports have Darwin kernel version in OSVersion field
  • 17017 Out of bounds unhandled exception
  • 17038 [wasm][xunit tests] RemoteExecutorTests.RemoteInvokeWritesToFile fails
  • 17040 [wasm][xunit tests] System.Net.Security.Tests.SslStreamAlpnTests - MissingMethodException: Default constructor not found
  • 17083 Regression: when debugger encounters a not-unhandled exception, it stops and shows “Dns.cs file not found” (Dns being the BCL class used)
  • 17084 Marshalling managed exception contains cut off stacktraces
  • 17133 SystemNative_CopyFile() call to fchmod() introduced in Mono 6.0 is not compatible with the external storage location on some Android OS versions and devices
  • 17139 mono_aot_register_module conflicting definitions
  • 17151 DriveInfo return empty space for system volume on MacOS 10.15 Catalina
  • 17180 [merp] mono_summarize_unmanaged_stack tries to take a lock while calling decode_exception_debug_info
  • 17278 System.BadImageFormatException when reflecting on BCL shipped with Mono
  • 17334 mono_magic_trampoline being called more than expected
  • 17335 Investigate heavy stack from System_Threading_Interlocked_Exchange_T_REF_T_REF__T_REF
  • 17419 [merp] generate a crash report if process is killed with SIGTERM
  • 17549 Debugging ‘async Task Name()' method makes app crash
  • 17569 Await within method with return type Task makes debugging fail
  • 17665 AOT + System.Reflection.Emit + ConstructorInfo doesn’t work as expected
  • 17687 [Regression] Profiler’s calls log SIGABRTs when using GDI+ loader
  • 17718 Delegate does not invoke target virtually
  • 17737 Q: is using loader lock for domain seq_points access correct? (mono runtime) [runtime] Fix locking in mono_get_seq_points ().
  • 17790 [merp] SendMicrosoftTelemetry icall doesn’t do any MERP logging when inducing a Managed Crash
  • 17833 threadpool hang due to unlimited hill climbing
  • 17878 Deadlock in GC during bridge callback from native thread on Android
  • 17924 Mtouch argument interpreter crashes EntityFrameworkCore 3.0 iOS app
  • 17926 [Bug] Segmentation Fault receiving message on WatchOS with debugger attached
  • 17931 Native linking fails for armv7s
  • 18011 [embedding] Chaining Mach exceptions to Mono signals using utility threads


Александр Хухлаев, Aaron Robinson, Adam Sitnik, Aleksey Kliger, Alex Thibodeau, Alexander Köplinger, Alexis Christoforides, Ankit Jain, Ben Adams, Bernhard Urban-Forster, Boris Parfenenkov, Calvin Buckley, Cody Russell, David Karlaš, Egor Bogatov, EgorBo, Eric Erhardt, Fan Yang, Filip Navara, Jan, Jan Kotas, Jay Krell, Jeffrey Zhao, Jo Shields, Johan Lorensson, John Salem, Jérôme Laban, Kenneth Pouncey, Kyle White, Larry Ewing, Levi Broderick, Marek Safar, Marius Ungureanu, Martin Baulig, Maxim Lipnin, Michal Strehovský, Nathan Ricci, Neale Ferguson, Next Turn, Nikita Voronchev, Nikolay Sivov, Phil Jaenke, Piotr Zierhoffer, Radek Doulik, Rolf Bjarne Kvinge, Ryan Lucia, Sam Patel, Santiago Fernandez Madero, Sebastien Pouliot, Steffen Kieß, Stephen Toub, Steve Pfister, Sung Yoon Whang, Sylvain, Tanner Gooding, Tarek Mahmoud Sayed, Thays Grazia, Tyler Brinkley, UnknownShadow200, Vincent Povirk, Vlad Brezae, Vladimir Sadov, Youssef Victor, Zoltan Varga, coypoop, iamphi, imhameed, lateralusX, madmir, naricc, obligaron