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Since C11 there is _Alignas(sizeof T), forcing one of the proposed meanings for alignment, and _Alignof(T), which queries actual (i.e. natural, per another meaning) alignment. But, yeah, the argument upthread seems more about the implicit meaning of natural than anything else.

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On that note, something that caught me off guard once is that C11 _Alignof and GCC __alignof__ can differ: for example in 32-bit x86 __alignof__(double) == 8 but _Alignof(double) == 4; however __alignof__(struct { double d; }) == 4. Apparently __alignof__ gives the preferred alignment whereas _Alignof gives the alignment required by ABI.

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