It's 10 pm, do you know what your JITter is doing?

Kristoffer — Fri, 13 Nov 2009 21:52:00 GMT

Ever have that awkward feeling like you don't know what actually gets executed as a result of your managed code? Visual Studio allows you to inspect the JITted code easily but does require a few tweaks first:

First set your project to build in Release mode.
Next go to Tools|Options|Debugging and uncheck both Suppress JIT optimization on module load (Managed only) and Enable Just My Code (Managed only)

Now you can run your project and set a breakpoint where you want to look at code and go to Debug | Windows | Disassembly to get an annotated disassembly like the following:

    static void Main(string[] args)
    {
        DoTest();
00000000 push ebp 
00000001 mov ebp,esp 
00000003 push esi 
00000004 call dword ptr ds:[00159B7Ch] 
        Console.WriteLine(s);
0000000a mov esi,dword ptr ds:[037D5B20h] 
00000010 call 6B20BE78 
00000015 mov ecx,eax 
00000017 mov edx,esi 
00000019 mov eax,dword ptr [ecx] 
0000001b call dword ptr [eax+000000D8h] 
00000021 pop esi 
    }
00000022 pop ebp 
00000023 ret  

OutOfMemoryException is special

Kristoffer — Wed, 25 Feb 2009 20:25:00 GMT

Consider the humble OutOfMemoryException and its most common usage. If it is thrown when the system is well and truly out of memory then how would the system allocate enough memory to create a new instance of OutOfMemoryException? Luckily this problem has a simple solution: OutOfMemoryException is allocated up front so it's available when it needs to be thrown.

The .NET runtime does first try to create a new OutOfMemoryException instance but if it fails it will fall back to the preallocated instance so there is always an exception available to be thrown.

Some other exceptions are preallocated: StackOverflowException, ExecutionEngineException, and ThreadAbortException.

Kristoffer's tidbits : .NET

It's 10 pm, do you know what your JITter is doing?

OutOfMemoryException is special