# Early Access Preview of Kotlin/Native #

## Introduction ##

 _Kotlin/Native_ is a LLVM backend for the Kotlin compiler. It consists of a machine code generation facility using
the LLVM toolchain and a native runtime implementation.

 _Kotlin/Native_ is primarily designed to allow compilation for platforms where
virtual machines are not desirable or possible (such as iOS or embedded targets),
or where the developer needs to produce a reasonably-sized self-contained binary
that doesn't require an additional execution runtime.

## Supported platforms ##

The _Kotlin/Native_ compiler produces mostly portable (modulo pointer size and target
triplet) LLVM bitcode, and as such can easily support any platform, as long as there's an LLVM
code generator for the platform.
 However, as actualy producing native code requires a platform linker and some
basic runtime shipped along with the translator, we only support a subset of all possible
target platforms. Currently _Kotlin/Native_ is being shipped and tested with support for
the following platforms:

 * Mac OS X 10.11 and later (x86-64), host and target (`-target macbook`, default on OSX hosts)
 * Ubuntu Linux x86-64 (14.04, 16.04 and later), other Linux flavours may work as well, host and target
   (`-target linux`, default on Linux hosts)
 * Microsoft Windows x86-64 (tested on Windows 7 and Windows 10), host and target (`-target mingw`,
   default on Windows hosts)
 * Apple iOS (arm64), cross-compiled target (`-target iphone`), hosted on OS X
 * Linux arm32 hardfp, Raspberry Pi, cross-compiled target (`-target raspberrypi`), hosted on Linux
 * Linux mips big endian, cross-compiled target (`-target mips`), hosted on Linux
 * Linux mips little endian, cross-compiled target (`-target mipsel`), hosted on Linux
 * Android arm32 and arm64 (`-target android_arm32` and `-target android_arm64`), target, hosted on Linux or OS X

 Adding support for other target platforms shouldn't be too hard, if LLVM support is available.

 ## Compatibility and features ##

To run _Kotlin/Native_ JDK8 for the host platform has to be installed.
Note that Java 9 not yet supported.

The language and library version supported by this EAP release mostly match Kotlin 1.2.
However, there are certain limitations, see section [Known Limitations](#limitations).

 Currently _Kotlin/Native_ uses reference counting based memory management scheme with a cycle
collection algorithm. Multiple threads could be used, but objects must be explicitly transferred
between threads, and same object couldn't be accessed by two threads concurrently.

_Kotlin/Native_ provides efficient interoperability with libraries written in C or Objective-C, and supports
automatic generation of Kotlin bindings from a C/Objective-C header file.
See the samples coming with the distribution.

  ## Getting Started ##

 Download _Kotlin/Native_ distribution and unpack it. You can run command line compiler with

    bin/kotlinc <some_file>.kt <dir_with_kt_files> -o <program_name>

  During the first run it will download all the external dependencies, such as LLVM.

To see the list of available flags, run `kotlinc -h`.

For documentation on C interoperability stubs see INTEROP.md.

 ## <a name="limitations"></a>Known limitations ##

 ### Performance ###

 *** DO NOT USE THIS PREVIEW RELEASE FOR ANY PERFORMANCE ANALYSIS ***

 This is purely a technology preview of _Kotlin/Native_ technology, and is not yet tuned
for benchmarking and competitive analysis of any kind.

### Standard Library ###

  The standard library in _Kotlin/Native_ is known to be mostly complete, please report us 
missing functionality. Note, that standard Java APIs, such as `java.lang.Math` or `java.io`
is not available in current _Kotlin_ standard library, but using C interoperability, one could
call similar APIs from the POSIX library, see this [`sample`](https://github.com/JetBrains/kotlin-native/blob/master/samples/csvparser).

### Reflection ###

Full reflection is not implemented, but class can be referenced and its name could be retrieved.
Notice that property delegation (including lazy properties) *does* work.

### Microsoft Windows support ###

 Only 64-bit Windows is currently supported as both compilation host and target.

### Debugging ###

 _Kotlin/Native_ supports preliminary source-level debugging on produced executables with `lldb` debugger.
 Produce your binary with debugging information by specifying `-g` _Kotlin/Native_ compiler switch.
 Konan plugin accepts `enableDebug` project's property, allowing two options for producing binaries with debug
 information:
   - gradle DSL.
   - argument `-PenableDebug=true` in gradle command line.

 Start your application with
    
    lldb my_program.kexe
 
 and then 
    
    b kfun:main(kotlin.Array<kotlin.String>)

to set breakpoint in main function of your application. Single stepping and step into shall work, 
variable inspection may have issues.
See [`DEBUGGING.md`](https://github.com/JetBrains/kotlin-native/blob/master/DEBUGGING.md)