Path.GetFullPath() bug demo

GetFullPathBugDemo.cs

using System;
using System.IO;

class GetFullPathBugDemo
{
	public static void Main(string[] args)
	{
		Console.WriteLine("Test with rooted path:");
		Console.WriteLine(Path.GetFullPath(Directory.GetCurrentDirectory() + @"/test//test//test//"));
		Console.WriteLine("Test with relative path:");
		Console.WriteLine(Path.GetFullPath(@"test//test//test//"));
	}
}

On Windows 10:

C:\temp>mono --version
Mono JIT compiler version 5.20.1 (Visual Studio built mono)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
        TLS:           __thread
        SIGSEGV:       normal
        Notification:  Thread + polling
        Architecture:  amd64
        Disabled:      none
        Misc:          softdebug
        Interpreter:   yes
        LLVM:          supported, not enabled.
        Suspend:       preemptive
        GC:            sgen (concurrent by default)

C:\temp>mono GetFullPathBugDemo.exe
Test with rooted path:
C:\temp\test\test\test\
Test with relative path:
C:\temp\test\test\test\

C:\temp>

On OpenBSD:

thfr@ryz.domain:tmp$ mono --version
Mono JIT compiler version 5.20.1.19 (tarball Mon Jun 24 09:30:38 MDT 2019)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           
	SIGSEGV:       normal
	Notification:  kqueue
	Architecture:  amd64
	Disabled:      none
	Misc:          softdebug 
	Interpreter:   yes
	LLVM:          supported, not enabled.
	Suspend:       cooperative
	GC:            sgen (concurrent by default)

thfr@ryz.domain:tmp$ mono ~/obsd/ports/mono/GetFullPathBugDemo.exe
Test with rooted path:
/tmp/test/test/test/
Test with relative path:
/tmp/test//test//test//

thfr@ryz.domain:tmp$

On Ubuntu:

thfr@thfr-MS-7B79:/tmp$ mono --version
Mono JIT compiler version 5.20.1.19 (tarball Thu Apr 11 09:02:17 UTC 2019)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           __thread
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  amd64
	Disabled:      none
	Misc:          softdebug 
	Interpreter:   yes
	LLVM:          yes(600)
	Suspend:       hybrid
	GC:            sgen (concurrent by default)

thfr@thfr-MS-7B79:/tmp$ mono GetFullPathBugDemo.exe
Test with rooted path:
/tmp/test/test/test/
Test with relative path:
/tmp/test//test//test//

thfr@thfr-MS-7B79:/tmp$