我可以安全地将第一个结构成员的地址解释为整个结构的地址吗？

Question

I'm implementing my own list similar to one from Linux list.h , but don't want to bother with container_of thing.

I've read that C compiler is not allowed to reorder struct members, but is there a guarantee that the first member's offset is always zero?

Can I just impose a restriction that list head member must be declared first to be able to get the whole struct member simply by casting head address to the container type?

Answer 1

From C standard

6.7.2.1 Structure and union specifiers

15 . Within a structure object, the non-bit-field members and the units in which bit-fields reside have addresses that increase in the order in which they are declared. A pointer to a structure object, suitably converted, points to its initial member (or if that member is a bit-field, then to the unit in which it resides), and vice versa . There may be unnamed padding within a structure object, but not at its beginning.

^{Emphasis mine}