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Type Erasure in C++

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One Box, Any Type: Understanding Type Erasure in C++ Or: How std::function stores a lambda, a function pointer, and a functor in the same box C++ rewards precise thinking about types. Most of the time, that precision is a feature. But occasionally the type system and the design pull in opposite directions, and the compiler rejects code that is, by every conceptual measure, reasonable. Consider a transaction monitor for a SystemC simulation. Every time a TLM transaction arrives, four separate objects need to respond: a Logger records it, a LatencyTracker measures it, a ProtocolChecker validates it, a CoverageCollector bins it. They share no base class, and they shouldn't need one. What they have in common is purely behavioral: they all respond to a transaction. So the obvious thing gets written: std :: vector < TransactionHandler > handlers ; handlers . push_back ( Logger {}); handlers . push_back ( LatencyTracker {}); handlers . push_back ( Pr...
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RAlI - The Silent Guardian of Your C++ Code

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RAII - The Silent Guardian of Your C++ Code How a destructor saved my multithreaded system late at night It was late at night. A multithreaded simulation platform had just frozen solid, no crash, no exception, no log entry. Just silence. The kind of silence that means every thread is waiting for every other thread, and nothing will ever move again. A deadlock. The engineer staring at the thread dump traced it back to an early-return path buried three call levels deep. Someone had locked a mutex, hit an error condition, returned immediately, and never unlocked. Under light load the path was never triggered. Under the stress of a parallel workload with dozens of threads hammering the same subsystem, it was only a matter of time. The mutex stayed locked. The threads piled up. The system seized. The lock had been acquired manually. It had been forgotten manually. These two facts were never meant to be separated and yet they were, by twelve lines of error-handling code a...
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Logarithms

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The Number That Barely Moves: CodePuz Mathematics · Algorithms · Intuition Most of What We Studied in School Stayed There Logarithms didn’t. They followed us into every codebase, quietly running inside the algorithms we rely on the most. There is a long list of things we studied in school mathematics and never encountered again. Trigonometric identities are near the top. Sin²θ + cos²θ = 1, the double angle formulae, pages of them, dutifully memorised and carefully reproduced in an exam, then quietly never thought about again. They had the decency to stay in school where we left them. Logarithms sat in the same chapter. Same compact notation, same air of abstraction, same unspoken question: when will I ever use this? So they got filed under the same heading: learned it, passed it, moved on. That turns out to be a significant mistake. Unlike most of what we memorised, logarithms never went away. They just went underground. There is one inside every binary searc...
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