"ioquatix (Samuel Williams) via ruby-core" <ruby-core@ml.ruby-lang.org> wrote:
- unicorn has merged a fix but it is not released: https://yhbt.net/unicorn.git/63c85c4282d15e22bd32a905883d2d0e149619d1/s/ - kgio has merged a fix but it is not released: https://yhbt.net/kgio.git/dbf5290cf9f89174f6b35a597af9a4226633d79b/s/ - raindrops merged a fix but it is not released: https://yhbt.net/raindrops.git/b3212417cc3e7cc44aa9e1ffe89b0d62ef3fdab5/s/
Still working on writing release notes and docs. <snip> sharing common struct fields example (more below)
However, we are not 100% confident this is safe according to the C specification. My experience is not sufficiently wide to say this is safe in practice, but it does look okay to both myself, and @Eregon + @tenderlovemaking have both given some kind of approval.
That being said, maybe it's not safe.
It's safe. Normal (unpacked) C structs have a well-defined and stable ABI. Ruby has been relying on it with RVALUE union and RBasic->flags for decades. FFI users all rely on this C ABI stability for calling C code w/o a C compiler. gcc and clang have a __transparent_union__ attribute designed to make migrations like this easy and painless for old code. rb_io_descriptor also introduces extra function call overhead.