Comment by flohofwoe

> struct layout is well specified

Technically that's not true at least for booleans and enums, the C standard doesn't define specific sizes for those (bools are commonly 1 byte though, but for enums at least MSVC likes to disagree with Clang and GCC).

Using a direct struct memory layout for persistency and then expecting it to work across compilers, CPUs and ABIs is almost guaranteed to cause problems.