Re: [PATCH] read-cache: avoid misaligned reads in index v4

Jeff King [off-list ref] writes:

Here (and elsewhere), you can assume that the offsetof() "sec" in
cache_time is 0, for two reasons:

  - I didn't look up chapter and verse, but I'm pretty sure the standard
    does guarantee that the first field of a struct is at the beginning.

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

6.7.2.1 #13 (page 103)

    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.

As an initial padding is forbidden, the first member's offset is zero.