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C++ Zero Overhead Pass by Value Through Invocable C++ Abstractions - Filipp Gelman - C++Now 2024
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This presentation focuses on what happens when non-trivial objects are passed to functions by value. Often this necessitates calling the copy or move constructor of the object's type. This call can be elided when the argument is a prvalue, such as when it is the result of another function or a temporary object of the expected type. The constructor can be elided even if the target function happens to be virtual.
But this doesn't work when invoking a std::function, std::move_only_function, std::function_ref, or even std::reference_wrapper. When the target of these abstractions takes objects by value, there will be at least one additional copy/move of the arguments even if they are prvalues.
But what if this were not the case?
This presentation will explain why library-level abstractions incur the overhead of an additional copy/move, and present a technique for avoiding this overhead. The following extreme example proves the point:
function＜void(lock_guard by_value)＞([](lock_guard by_value){});
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Slides: github.com/boo...
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Filipp Gelman
At Bloomberg LP since 2016, Filipp enjoys exploring the obscure, arcane, and esoteric corners of the C++ language. He is known among his coworkers for heavy use of templates, emphasis on compile time computation, and abusing language features for nefarious purposes.
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C++Now 2025 - 28th April - 2nd May
C++Now is an annual onsite international C++ programming and coding conference held in Aspen, Colarado. For all C++ developers, C++ software engineers and those involved with the C++ language, CppNow provides an indepth and technical content provided by the best and brightest C++ experts of the C++ world.
Annual CppNow Conference - www.cppnow.org
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20 сен 2024
