问题
Suppose I have a templated function that deals with pointers to yet unknown type T. Now if type T happens to be void* on 64-bit platform then it must be 8-bytes aligned, but if T happens to be char it must be 1-byte aligned and if T happens to be a class then its alignment requirements will depend on its member variables.
This all can be computed on paper, but how do I make the compiler yield the alignment requirements for a given type T?
Is there a way to find during compile time the alignment requirements for a given type?
回答1:
In C++11 you can use alignof and alignas to make asserts and provide requirements for alignment. Also look at std::align to control alignment in runtime.
回答2:
In the absence of C++11, its easiest to use the next power-of-two greater than or equal to sizeof(T). You might also want to cap it to the alignment of the largest primitive. 8 is a pretty safe bet on a 64-bit architecture (though you might need to keep an eye on things like SSE data types).
来源：https://stackoverflow.com/questions/13249841/how-do-i-check-a-typed-pointer-is-properly-aligned-for-that-type