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Rust doesn't currently guarantee ABI compatibility. You can't load Rust from a shared library without going via repr(C) anyway. I imagine that the algorithm w

Rust doesn't currently guarantee ABI compatibility. You can't load Rust from a shared library without going via repr(C) anyway. I imagine that the algorithm will be frozen whenever we get to this point, but it shouldn't need to change again unless someone tries to take us as far as what Swift does (which would potentially be a much bigger project than this). There's also been discussion of giving you tools to control it more explicitly, but thus far no one has proposed an RFC.

phkahler 9y ago
>> Rust doesn't currently guarantee ABI compatibility. And yet they claim it's a systems programming language. While I can see the value in doing this, I can see the value in doing it manually. Another criteria can be putting the most frequently used fields together, so accessing one causes the others to load in the same cache line. In many programs the size of the structure is not important, it's the cache behavior that is and that is dependent on a lot more than the size of the elements alone. It's probably important that it can be disabled with rear(C).
- kibwen 9y ago
  > And yet they claim it's a systems programming language. C++ also doesn't guarantee a stable ABI, and even the C ABI is only de facto standardized on various platforms, nothing is provided by the language standard itself.
  - dom0 9y ago
    C and C++ ABI is implementation defined. All major platforms have a standard ABI for both, although sometimes it's broken intentionally. E.g. MinGW uses a GCC/Linux-like C++ ABI and not the MSVC C++ ABI. Note that "platform" means e.g. Linux-x86-64 and not Linux. Linux-ppc has different rules, for example.
    - jjnoakes 9y ago
      Not true for c++ unless you include the compiler and version in your "platform".
  - cryptonector 9y ago
    But then again, C++ isn't really a systems programming language, though a subset can be. The C ABIs are basically the ABIs published by each OS on each architecture, and typically they derive these from the ABIs published by the CPU vendors. Third party C compilers are expected to adhere to a platform's C ABI, and generally they do. Rust absolutely could be a systems programming language, but it will need at least repr(C) and such options to interface with: a) hardware, b) code not written in Rust or compiled with a different version of the Rust compiler. Sometimes (b) means "with itself", e.g., via structs saved in files with no additional encoding.
- jeffdavis 9y ago
  Rather than manually, how about with a tool assist?
- dbaupp 9y ago
  Your exact concern was raised and discussed earlier: https://news.ycombinator.com/item?id=14123252 https://news.ycombinator.com/item?id=14123252

phkahler 9y ago

>> Rust doesn't currently guarantee ABI compatibility. And yet they claim it's a systems programming language. While I can see the value in doing this, I can see the value in doing it manually. Another criteria can be putting the most frequently used fields together, so accessing one causes the others to load in the same cache line. In many programs the size of the structure is not important, it's the cache behavior that is and that is dependent on a lot more than the size of the elements alone. It's probably important that it can be disabled with rear(C).

kibwen 9y ago
> And yet they claim it's a systems programming language. C++ also doesn't guarantee a stable ABI, and even the C ABI is only de facto standardized on various platforms, nothing is provided by the language standard itself.
- dom0 9y ago
  C and C++ ABI is implementation defined. All major platforms have a standard ABI for both, although sometimes it's broken intentionally. E.g. MinGW uses a GCC/Linux-like C++ ABI and not the MSVC C++ ABI. Note that "platform" means e.g. Linux-x86-64 and not Linux. Linux-ppc has different rules, for example.
  - jjnoakes 9y ago
    Not true for c++ unless you include the compiler and version in your "platform".
- cryptonector 9y ago
  But then again, C++ isn't really a systems programming language, though a subset can be. The C ABIs are basically the ABIs published by each OS on each architecture, and typically they derive these from the ABIs published by the CPU vendors. Third party C compilers are expected to adhere to a platform's C ABI, and generally they do. Rust absolutely could be a systems programming language, but it will need at least repr(C) and such options to interface with: a) hardware, b) code not written in Rust or compiled with a different version of the Rust compiler. Sometimes (b) means "with itself", e.g., via structs saved in files with no additional encoding.
jeffdavis 9y ago
Rather than manually, how about with a tool assist?
dbaupp 9y ago
Your exact concern was raised and discussed earlier: https://news.ycombinator.com/item?id=14123252 https://news.ycombinator.com/item?id=14123252