[Mono-bugs] [Bug 78633][Cri] New - Serious bug in lock - locks not unlocked on exception

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Changed by vargaz at gmail.com.

http://bugzilla.ximian.com/show_bug.cgi?id=78633

--- shadow/78633	2006-06-13 12:27:11.000000000 -0400
+++ shadow/78633.tmp.13049	2006-06-13 12:27:11.000000000 -0400
@@ -0,0 +1,122 @@
+Bug#: 78633
+Product: Mono: Runtime
+Version: 1.1
+OS: other
+OS Details: CentOS 4
+Status: RESOLVED   
+Resolution: FIXED
+Severity: Unknown
+Priority: Critical
+Component: misc
+AssignedTo: mono-bugs at ximian.com                            
+ReportedBy: nikki at trumphurst.com               
+QAContact: mono-bugs at ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: Serious bug in lock - locks not unlocked on exception
+
+Please fill in this template when reporting a bug, unless you know what 
+you are doing.
+Description of Problem:
+
+It is possible to execute code which throws an Exception inside a lock 
+statement which exits the statement without releasing the lock.
+Steps to reproduce the problem:
+1. Compile attached code with  mcs -codepage:1252 -optimize- -delaysign- -
+target:winexe -r:"System.dll" -r:"System.Data.dll" Test.cs
+
+2. Run with mono Test.exe
+
+Actual Results:
+Error thread initial sleep
+Main thread initial sleep
+Returning null from NextError
+Trying
+Trying to lock error -1090733248
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Returning null from NextError
+Error thread exiting
+[program now hangs forever, waiting for the lock]
+
+Expected Results:
+Main thread obtains lock and program exits normally.
+
+How often does this happen? 
+Every time
+
+Additional Information:
+Here is the code to reproduce the problem...
+
+using System;
+using System.Threading; 
+
+namespace SpecSoft.Lib {
+
+	public class Test {
+
+		private static Object _error = new Object();
+
+		public static void Main() {
+			Thread _errorThread = new Thread(new ThreadStart
+(errorThread));
+
+			_errorThread.IsBackground = true;
+			_errorThread.Name = "Error reporting thread";
+			_errorThread.Start();
+			System.Console.WriteLine("Main thread initial 
+sleep");
+			Thread.Sleep(2000);
+			System.Console.WriteLine("Trying");
+			System.Console.WriteLine("Trying to lock error 
+{0}", _error.GetHashCode());
+			lock(_error) {
+				System.Console.WriteLine("Locked error");
+			}
+			System.Console.WriteLine("Unlocked error");
+		}
+
+		private static void errorThread() {
+			System.Console.WriteLine("Error thread initial 
+sleep");
+			Thread.Sleep(1000);
+			for(int i = 0; i < 10; i++) {
+				NextError();
+				Thread.Sleep(1000);
+			}
+			System.Console.WriteLine("Error thread exiting");
+		}
+
+		public static string NextError() {
+			try {
+				lock(_error) {
+					string [] files = new string[1];
+
+					return files[2];	
+	// Throws an exception
+				}
+			} catch {
+			}
+			System.Console.WriteLine("Returning null from 
+NextError");
+			return null;
+		}
+
+	}
+}
+
+------- Additional Comments From nikki at trumphurst.com  2006-06-13 10:44 -------
+The problem goes away if you change the empty catch statement in 
+NextError from "} catch {" to "} catch(Exception ex) {", so maybe 
+the bug is in the compiler?
+
+------- Additional Comments From vargaz at gmail.com  2006-06-13 12:27 -------
+Fixed in SVN.
+