`alignas` specifier (since C++11)

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Compiler support
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Standard library
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Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
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Ranges library (C++20)
Algorithms library
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Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)

alignas specifier (since C++11)