alt Hacker NewsC++ ABI stability is the main reason improvements to the language get rejected.
You cannot change anything that would affect the class layout of something in the STL. For templated functions where the implementation is in the header, ODR means you can't add optimizations later on.
Maybe this was OK in the 90s when companies deleted the source code and laid off the programmers once the software was done, but it's not a feature Rust should ever support or guarantee.
The "stable ABI" is C functions and nothing else for a very good reason.
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What's the stat of single-compiler version ABI? I mean - if the compiler guaranteed that for the same version of the compiler the ABI can work, we could potentially use dynamic linking for a lot of things (speed up iterative development) without committing to any long term stable API or going through C ABI for everything.
The big question is does Rust want to play being adopted by those vendors, or it would leave them alone with languages that embrace native libraries.
I think if Rust wants to evolve even more aggressively than C++ evolves, then that is a chasm that needs to be crossed.
In lots of domains, having a language that doesn't change very much, or that only changes very carefully with backcompat being taken super seriously, is more important than the memory safety guarantees Rust offers.