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Because in practice the Go solution is the other way around: You can optionally decide to worry about it by turning on the linter that detects this. It's not a

by jerf 5y ago

Because in practice the Go solution is the other way around: You can optionally decide to worry about it by turning on the linter that detects this. It's not a very different solution in practice. I actually kind of like the idea of a minimal language with a robust linting/static analysis community. You can modularly pick what things you want to worry about. The correct answer for the vast bulk of Go programmers is not to worry about this, and the ones who want to, the tools are readily available and already integrated into a tool that anyone writing serious Go code should already be using.

kibwen 5y ago
> It's not a very different solution in practice. It makes a difference in the presence of generics, since at that point laying out fields efficiently in the face of every possible combination of types is a task that only the compiler can perform. There's nothing that says that it needs to be the default behavior, but if you want efficient space usage then you need more than a lint, you need some way to enable automatic field reordering.
- jerf 5y ago
  Fair enough, I don't think of generics as quite existing yet so I haven't started considering them yet. I suspect in practice we're not going to see a lot of structs with a bajillion generics in them, though. Generics are going to solve the problems the Go developers said they will solve but there's still just enough friction in them (particularly the inability to introduce new types in methods) that I expect it will not be practical to create C++-like libraries of generic things that take generics that take generics as arguments, and in practice, "stick the small number of generic things (most likely one) at the end of the struct" will mostly cover the bases. (I have no problem saying that if you need the n'th degree in performance, you shouldn't have picked Go. I think it has a great bang-for-the-buck ratio, but it definitely does not occupy the "best possible performance" slot.)
  - kibwen 5y ago
    > I suspect in practice we're not going to see a lot of structs with a bajillion generics in them Sure, but note that it only takes a single generic parameter to exhibit this behavior. Consider the original struct definition in the OP: if we imagine that the first field was generic instead of uint8, then the struct has padding only when the type is less than 16 bits in size. No matter where you manually reorder that field, some possible types will still result in padding if the fields are forced to be laid out in order, and it took no more than a single type parameter.

by jerf 5y ago

kibwen 5y ago

> It's not a very different solution in practice. It makes a difference in the presence of generics, since at that point laying out fields efficiently in the face of every possible combination of types is a task that only the compiler can perform. There's nothing that says that it needs to be the default behavior, but if you want efficient space usage then you need more than a lint, you need some way to enable automatic field reordering.

jerf 5y ago
Fair enough, I don't think of generics as quite existing yet so I haven't started considering them yet. I suspect in practice we're not going to see a lot of structs with a bajillion generics in them, though. Generics are going to solve the problems the Go developers said they will solve but there's still just enough friction in them (particularly the inability to introduce new types in methods) that I expect it will not be practical to create C++-like libraries of generic things that take generics that take generics as arguments, and in practice, "stick the small number of generic things (most likely one) at the end of the struct" will mostly cover the bases. (I have no problem saying that if you need the n'th degree in performance, you shouldn't have picked Go. I think it has a great bang-for-the-buck ratio, but it definitely does not occupy the "best possible performance" slot.)
- kibwen 5y ago
  > I suspect in practice we're not going to see a lot of structs with a bajillion generics in them Sure, but note that it only takes a single generic parameter to exhibit this behavior. Consider the original struct definition in the OP: if we imagine that the first field was generic instead of uint8, then the struct has padding only when the type is less than 16 bits in size. No matter where you manually reorder that field, some possible types will still result in padding if the fields are forced to be laid out in order, and it took no more than a single type parameter.