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为了使它具体,我只想知道为什么在我的64位mac上,Swift编译器说某些类型的对齐方式Float80是16. 要检查类型的内存对齐要求,我使用该alignof函数.

sizeof(Float80) // ~> 16 bytes, it only needs 10 bytes, but because of hardware design decisions it has to be a power of 2
strideof(Float80) // ~> 16 bytes, clear because it is exact on a power of 2, struct types with Float80 in it, can be bigger
alignof(Float80) // ~> 16 bytes, why not 8 bytes, like String ?

我理解类型的内存对齐小于或等于单词的大小是有益的.

sizeof(String) // ~> 24 bytes, clear because 24 is multiple of …