Conditional compilation

While Inko code is portable across platforms and architectures, sometimes you need to handle differences in the underlying platforms, most commonly when using the FFI.

Inko supports conditional compilation at the import level only. This makes it easier to understand the code, as platform specific code ends up in dedicated modules.

For example, to import the module foo only on amd64 Linux platforms, you'd write the following:

import foo if linux and amd64

Compiling conditional imports

The tags act as an AND, meaning the import is only processed if all the specified tags are available. OR expressions and negations aren't supported, but OR expressions can be handled by just using separate imports:

import foo if linux
import foo if mac

Build tags are applied when parsing Inko source modules to an AST, and imports that should be ignored based on the build tags are removed when lowering to HIR.

This means that if a conditionally compiled module includes any errors (e.g. a type error), those errors won't surface until you compile the code such that all build tags are available. In other words: if you have a import foo if mac statement, and the foo module contains any errors, you won't see those errors until you compile your code for/on macOS.

The compiler won't produce any errors for tags it doesn't recognise, meaning the following import is never processed:

import foo if kittens

Available build tags

Note

Custom build tags aren't supported, nor are we likely to support them any time soon as this complicates the build process.

The following tags are available, and are based on the target an Inko program is compiled for:

Tag	Meaning
amd64	The platform is a 64-bits x86 platform
arm64	The platform is a 64-bits ARM platform
freebsd	The target OS is FreeBSD
mac	The target OS is macOS
linux	The target OS is Linux
bsd	The target OS is any BSD
unix	The target OS is any Unix system
gnu	The target uses the GNU ABI
native	The target uses the native ABI

The bag bsd is essentially (freebsd OR ...), while unix is essentially (freebsd or linux or mac or ...).

For Linux targets using glibc, the ABI is gnu instead of native. For the time being the ABI tags aren't useful, but in the future we may support both musl and GNU builds, at which point they can be useful to handle differences between the two libc implementations.