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POSame IL code, different output - how is it possible?
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copied!<p>I have a piece of code, which outputs different results, depending on the C# compiler and the runtime.</p> <p>The code in question is:</p> <pre><code>using System; public class Program { public static void Main() { Console.WriteLine(string.Compare("alo\0alo\0", "alo\0alo\0\0", false, System.Globalization.CultureInfo.InvariantCulture)); } } </code></pre> <p>The results are:</p> <pre><code> Compiling with mono (gmcs) Compiling with .Net (csc) Running with mono -1 -1 Running with .Net -1 0 </code></pre> <p>How can it output different values, when running with the .Net framework?</p> <p>(BTW, according to <a href="http://msdn.microsoft.com/en-us/library/system.string.aspx" rel="noreferrer">http://msdn.microsoft.com/en-us/library/system.string.aspx</a> the output should be 0, so mono's answer is incorrect, but that's unrelated to my question.)</p> <p>Even the generated IL code is (almost) the same.</p> <p>Compiling with .Net:</p> <pre><code>.method public hidebysig static void Main() cil managed { .entrypoint // Code size 29 (0x1d) .maxstack 8 IL_0000: nop IL_0001: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o... IL_0006: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 // a.l.o...a.l.o... 00 00 ) IL_000b: ldc.i4.0 IL_000c: call class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture() IL_0011: call int32 [mscorlib]System.String::Compare(string, string, bool, class [mscorlib]System.Globalization.CultureInfo) IL_0016: call void [mscorlib]System.Console::WriteLine(int32) IL_001b: nop IL_001c: ret } // end of method Program::Main </code></pre> <p>Compiling with mono:</p> <pre><code>.method public hidebysig static void Main() cil managed { .entrypoint // Code size 27 (0x1b) .maxstack 8 IL_0000: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o... IL_0005: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 // a.l.o...a.l.o... 00 00 ) IL_000a: ldc.i4.0 IL_000b: call class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture() IL_0010: call int32 [mscorlib]System.String::Compare(string, string, bool, class [mscorlib]System.Globalization.CultureInfo) IL_0015: call void [mscorlib]System.Console::WriteLine(int32) IL_001a: ret } // end of method Program::Main </code></pre> <p>The only difference is the two extra NOP instructions in the .Net version.</p> <p>How is it possible? How can the two output values be different?</p> <p>Also, if anyone has both .Net and mono installed, can you reproduce it?</p> <p>EDIT: <em>I don't care</em> what the correct result is, and <em>I don't care</em> that mono and .Net produces different results. I'll probably never encounter embedded nulls AND sort them AND the sorting order will be important.</p> <p>My problem is that the same <em>runtime</em> (.Net 2.0) produces different results, when <em>compiled</em> by different compilers.</p> <p>EDIT 2: I added a table and tried to clarify the question, it should be easier to understand now.</p>

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