[Mono-bugs] [Bug 435747] New: gmcs improperly compiles multiple value-type assignments on a single line.

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Wed Oct 15 13:25:12 EDT 2008


           Summary: gmcs improperly compiles multiple value-type assignments
                    on a single line.
           Product: Mono: Compilers
           Version: 2.0
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: C#
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: peter at peterjohanson.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---

I found this funkiness while using Mono 2.0:

Consider the following lines:

DateTime dt;

DateTime other_dt = dt = new DateTime (633596616517216000);
Console.WriteLine ("other_dt: {0}, dt: {1}", other_dt, dt);

DateTime other_dt2 = dt = DateTime.Now;
Console.WriteLine ("other_dt2: {0}, dt: {1}", other_dt2, dt);

One would expect other_dt and dt to be equal, and later, for other_dt2 to be
equal to dt.

However, with mono 2.0, the following IL snippet gets generated:

        .locals init (
                valuetype [mscorlib]System.DateTime     V_0,
                valuetype [mscorlib]System.DateTime     V_1,
                valuetype [mscorlib]System.DateTime     V_2) 
        IL_0000:  ldloca.s 1
        IL_0002:  ldc.i8 0x8cafcc40a65e700
        IL_000b:  call instance void valuetype
        IL_0010:  ldstr "other_dt: {0}, dt: {1}"
        IL_0015:  ldloc.1 
        IL_0016:  box [mscorlib]System.DateTime
        IL_001b:  ldloc.0 
        IL_001c:  box [mscorlib]System.DateTime
        IL_0021:  call void class [mscorlib]System.Console::WriteLine(string,
object, object)
        IL_0026:  call valuetype [mscorlib]System.DateTime valuetype
        IL_002b:  dup 
        IL_002c:  stloc.0 
        IL_002d:  stloc.2 
        IL_002e:  ldstr "other_dt2: {0}, dt: {1}"
        IL_0033:  ldloc.2 
        IL_0034:  box [mscorlib]System.DateTime
        IL_0039:  ldloc.0 
        IL_003a:  box [mscorlib]System.DateTime
        IL_003f:  call void class [mscorlib]System.Console::WriteLine(string,
object, object)

As you can see, the V_0 local *never* gets set for the first case. Test case
attached. I can post the IL generated by csc from MS .NET 2.0 if you would like
to compare.

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