Bug 20603 - Unreachable local variable declaration causing MCS to crash
Summary: Unreachable local variable declaration causing MCS to crash
Status: RESOLVED FIXED
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 3.2.x
Hardware: PC Linux
: --- normal
Target Milestone: ---
Assignee: Marek Safar
URL:
Depends on:
Blocks:
 
Reported: 2014-06-15 13:56 UTC by neil.sculthorpe
Modified: 2014-06-16 05:58 UTC (History)
1 user (show)

Tags:
Is this bug a regression?: ---
Last known good build:


Attachments
Minimal bug file causing MCS to crash (108 bytes, text/x-csharp)
2014-06-15 13:56 UTC, neil.sculthorpe
Details


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Status:
RESOLVED FIXED

Description neil.sculthorpe 2014-06-15 13:56:32 UTC
Created attachment 7078 [details]
Minimal bug file causing MCS to crash

Compiling the following problem,

class Program {
  public static void Main() {
         goto L1;
         int z;
     L1: z = 3;
  }
}

causes the MCS compiler (v3.2.8.0, on Ubuntu 14.04) to crash with the following error:

Unhandled Exception:
Mono.CSharp.InternalErrorException: Labels.cs(3,22): Program.Main() ---> Mono.CSharp.InternalErrorException: Labels.cs(3,29): ---> System.NullReferenceException: Object reference not set to an instance of an object

However, a similar program compiles and runs successfully:

class Program {
  public static void Main() {
         int x = 7;
         if (x > 0) {goto L1;}
         int z;
     L1: z = 3;
         System.Console.WriteLine(z);
  }
}

I speculate that in the former program, an optimisation is deleting "int z" as unreachable-code.  In the latter program, making "x" a "const" variable also triggers the error.
Comment 1 Marek Safar 2014-06-16 05:58:29 UTC
Fixed in master