Usage of _Alignas

[supple mulch]

What are actual usages of _Alignas operator?

I mean, I know what it does, but I think that I only ever had once a need to control some alignment, and it was when writing an allocator based on a unsigned char [] array. This actually triggers UB. as it violates strict aliasing rules. (unless you have some pointer laundry or know a bit about your compiler. but anyway this is not the point)

however, such case feels quite niche and I'm wondering why would one need such operator in practice?

[gritty fern]

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[clever wolf]

the roposal to add _Alignas to C https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1335.pdf is based on this proposal (cpp) https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2341.pdf which contains the motivation under 'problem targeted'

https://learn.microsoft.com/en-us/cpp/c-language/alignment-c?view=msvc-170 aslo provide some motivation generally cache related