Note that although alignment and size are platform-specific, in practice padding can be minimized simply by using a fixed order: (various vector types) int

Note that although alignment and size are platform-specific, in practice padding can be minimized simply by using a fixed order: (various vector types) int128_t long double long long, int64_t, int_fast64_t, double off_t time_t (can be 64 bits on 32-bit platforms only if off_t also is) register_t, int_fast16_t, int_fast32_t (64-bit on e.g. x32) void *, void(*)(), intptr_t ptrdiff_t (theoretically wrong if fully aligned and bigger than pointer) size_t, ssize_t long (32-bit on win64; generally has 16-bit alignment if bigger than pointer) int32_t, float int (can be 16-bit) short, int16_t char, bool, int8_t, int_fast8_t (a trailing array member must come last; note when calculating combined size you should use offsetof instead of sizeof to not waste padding) Besides this, `int_leastN_t` goes with `intN_t`, and all unsigned types go with their signed types. Note that types like `id_t` are hard to place however. Although there do exist many platforms where this is not in order of size, the bigger types generally have smaller alignment on such platforms. Despite this I have split out rows occasionally despite not knowing of any such platform.