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C++ - Optimizing away vtable with metaprogramming


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In every object oriented language class inheritance is a life saver when it comes to program architecture. A rather nasty side effect that comes with it is usually performance degradation. And in C++ that penalty can be quite noticeable. When working with virtual methods in derived classes compiler generates vtable (Virtual Method Table), where address for each overridden method is specified. Vtable is then used every time virtual method is called to lookup that address, jump to it and execute code at that location. That penalty can quickly increase execution time by \(\). There is a neat trick that allows us to resolve those addresses compile-time allowing compiler to optimize vtable away using metaprogramming.

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C++ - The value of ESP was not properly saved across a function call

Run-Time Check Failure #0 - The value of ESP was not properly saved across a function call.  This is usually a result of calling a function declared with one calling convention with a function pointer declared with a different calling convention.

Another run time error that is almost impossible to quickly identify and debug. It usually occurs when libraries are involved and use different calling conventions e.g. _stdcall instead of _cdecl or other. But sometimes compiler misses a thing or two and compiles something that it shouldn't, after all, compiler only need to know how many bits and bytes to move and what do to with them to translate your program to an executable or a library. Sometimes it lets you do stupid things...

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