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August 2007
September 2007

2007-08-24 »

More on preprocessors

pcolijn points out that in my earlier article about the C preprocessor I missed an important part about Java logging, namely that you can delay expensive object-to-string computations until inside the function call itself, because your log function can take a bunch of Object elements as parameters.

That's actually a really neat trick that I hadn't thought of. In C++ it's hard to do because there's no common-to-everyone Object class with a toString() type method, and auto-casting everything into any kind of Object would be expensive.

Now, to get a hexdump() as in my specific example, you'd need to write some kind of HexDumper class with a toString() method that actually does the hexdump. It would be a little strange, but mostly harmless. The trick would work in C# too.

I mostly write this because the program I was debugging last night was written in C, but didn't use the preprocessor trick for its logging, so I ran into exactly the performance program I was talking about. Ha ha, very funny, universe.

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