The Hive Tour
ENPT
1. Hello, World2. Running these examples3. Comments4. Names have shapes5. Variables and constants6. Scalar types7. Strings8. Operators9. Arithmetic at the edges10. Control flow11. assert and panic12. Vectors13. Builtins14. Bounds, proved at compile time15. A length is a promise16. Tables and CSV17. Result<T, E>18. Declared types19. Pattern matching with is20. func vs proc21. Named arguments22. First-class functions23. Mutability and value semantics24. Concurrency25. Generics26. Modules27. Importing a Go file28. Maps29. Conversions30. Math31. JSON32. Files33. Spreadsheets34. Terminal and processes35. Time36. Environment variables37. Networking: HTTP38. Networking: WebSockets39. Networking: raw TCP40. Cryptography41. SQL42. Optional filters: WHERE { }43. The in-memory trap44. The UI module45. Drawing on a canvas46. Three dimensions47. A sound is a shape48. Testing49. Distributed actors50. What an error looks like51. Building for another platform52. Containers53. Where to go next
Slide 51 of 53

Building for another platform

One machine, three platforms
$ hive build main.hive
Compiled main.hive -> main (1s)

$ hive build main.hive --target linux/arm64
Compiled main.hive -> main-linux-arm64 (2s)

$ hive build main.hive --target=windows/amd64
Compiled main.hive -> main-windows-amd64.exe (2s)
The three ways it says no
$ hive build main.hive --target linux/sparc
hive: `--target linux/sparc` is not a platform the Go toolchain builds for. A target is a `goos/goarch` pair — `linux/arm64`, `darwin/arm64`, `windows/amd64` — and `go tool dist list` names every one it knows.

$ hive build main.hive --target
hive: `--target` was given no platform to build for. It takes a `goos/goarch` pair — `hive build <entrypoint.hive> --target linux/arm64`.

$ hive check main.hive --target linux/arm64
hive: `--target` is a flag of `hive build`. `check` builds nothing for another platform.
Because the last step is the Go toolchain, a Hive program is built for another platform the way any Go program is — by telling the toolchain which one. hive build takes a --target, and nothing else does.A target is a goos/goarch pair, and the pair is checked before anything is compiled. `go tool dist list` names every one the toolchain knows, and one it does not name is refused there and then rather than ten seconds later, by a build failing in a language you did not write. The list is asked for rather than kept anywhere, so a platform Go learns tomorrow needs no change here. And a platform that does not exist is a mistake in what was typed, so it is reported as one — beside the other command-line mistakes, rather than against a line of a program that has nothing wrong with it.What comes out says what it is for. A host build of main.hive is main, and a cross build is main-linux-arm64: two files that cannot run in the same places must not answer to one name, and a cross build that quietly replaced the local one would only be found out by running it. The .exe follows the target rather than the machine, so --target windows/amd64 writes main-windows-amd64.exe from anywhere.CGO_ENABLED=0 goes with a cross build and only with one. Everything the runtime is made of is Go, so no Hive program needs a C compiler — and a C cross-compiler is the one thing a machine with the Go toolchain on it cannot be assumed to have. A build for the machine it is running on is given no environment at all, and is therefore byte for byte the build it always was.--target is a flag of build, and of build alone. check and emit compile nothing; test and container are both about this machine; and each of the four refuses the flag rather than accepting it and quietly ignoring it. run is the exception that proves the rule: everything after the entrypoint there belongs to the program being run, so a --target written after it is passed straight through, unread.
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