From: "mame (Yusuke Endoh) via ruby-core" Date: 2024-03-20T13:02:50+00:00 Subject: [ruby-core:117262] [Ruby master Feature#19057] Hide implementation of `rb_io_t`. Issue #19057 has been updated by mame (Yusuke Endoh). ioquatix (Samuel Williams) wrote in #note-43: > Here is the revert PR: https://github.com/ruby/ruby/pull/10283 Thanks! Just FYI, I think the precedence in Ruby's decision is basically: * beauty of the language (conciseness and intuitiveness for users) >= compatibility > runtime performance and efficiency >>> beauty of the implementation (simplicity for the core developers). Compared to the past, compatibility has become much more of a priority, and performance has become somewhat more important. The order is sometimes reversed in rare cases, but the beauty of the implementation has always been the lowest priority. The "beauty of the implementation", such as hiding the rb_io_t implementation, can beat "compatibility" only in limited and special cases, e.g., only when there is no other way at all, or when the practical impact is very small (no affected gem is identified, or it is only an issue with minor gems). In this case, unicorn, which is undeniably an important gem and still part of the Ruby ecosystem, is affected and there are known implementation workarounds. In that case, there is no reason not to choose the workaround. ---------------------------------------- Feature #19057: Hide implementation of `rb_io_t`. https://bugs.ruby-lang.org/issues/19057#change-107355 * Author: ioquatix (Samuel Williams) * Status: Assigned * Assignee: ioquatix (Samuel Williams) * Target version: 3.4 ---------------------------------------- In order to make improvements to the IO implementation like , we need to add new fields to `struct rb_io_t`. By the way, ending types in `_t` is not recommended by POSIX, so I'm also trying to rename the internal implementation to drop `_t` where possible during this conversion. Anyway, we should try to hide the implementation of `struct rb_io`. Ideally, we don't expose any of it, but the problem is backwards compatibility. So, in order to remain backwards compatibility, we should expose some fields of `struct rb_io`, the most commonly used one is `fd` and `mode`, but several others are commonly used. There are many fields which should not be exposed because they are implementation details. ## Current proposal The current proposed change creates two structs: ```c // include/ruby/io.h #ifndef RB_IO_T struct rb_io { int fd; // ... public fields ... }; #else struct rb_io; #endif // internal/io.h #define RB_IO_T struct rb_io { int fd; // ... public fields ... // ... private fields ... }; ``` 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. There are two alternatives: ## Hide all details We can make public `struct rb_io` completely invisible. ```c // include/ruby/io.h #define RB_IO_HIDDEN struct rb_io; int rb_ioptr_descriptor(struct rb_io *ioptr); // accessor for previously visible state. // internal/io.h struct rb_io { // ... all fields ... }; ``` This would only be forwards compatible, and code would need to feature detect like this: ```c #ifdef RB_IO_HIDDEN #define RB_IOPTR_DESCRIPTOR rb_ioptr_descriptor #else #define RB_IOPTR_DESCRIPTOR(ioptr) rb_ioptr_descriptor(ioptr) #endif ``` ## Nested public interface Alternatively, we can nest the public fields into the private struct: ```c // include/ruby/io.h struct rb_io_public { int fd; // ... public fields ... }; // internal/io.h #define RB_IO_T struct rb_io { struct rb_io_public public; // ... private fields ... }; ``` ## Considerations I personally think the "Hide all details" implementation is the best, but it's also the lest compatible. This is also what we are ultimately aiming for, whether we decide to take an intermediate "compatibility step" is up to us. I think "Nested public interface" is messy and introduces more complexity, but it might be slightly better defined than the "Current proposal" which might create undefined behaviour. That being said, all the tests are passing. -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/