2014-08-13 12:09:53 +00:00
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# xgo - Go CGO cross compiler
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2014-08-06 20:55:14 +00:00
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2014-08-07 07:05:33 +00:00
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Although Go strives to be a cross platform language, cross compilation from one
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platform to another is not as simple as it could be, as you need the Go sources
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bootstrapped to each platform and architecture.
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The first step towards cross compiling was Dave Cheney's [golang-crosscompile](https://github.com/davecheney/golang-crosscompile)
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package, which automatically bootstrapped the necessary sources based on your
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existing Go installation. Although this was enough for a lot of cases, certain
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drawbacks became apparent where the official libraries used CGO internally: any
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dependency to third party platform code is unavailable, hence those parts don't
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cross compile nicely (native DNS resolution, system certificate access, etc).
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A step forward in enabling cross compilation was Alan Shreve's [gonative](https://github.com/inconshreveable/gonative)
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package, which instead of bootstrapping the different platforms based on the
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existing Go installation, downloaded the official pre-compiled binaries from the
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golang website and injected those into the local toolchain. Since the pre-built
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binaries already contained the necessary platform specific code, the few missing
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dependencies were resolved, and true cross compilation could commence... of pure
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Go code.
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However, there was still one feature missing: cross compiling Go code that used
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CGO itself, which isn't trivial since you need access to OS specific headers and
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libraries. This becomes very annoying when you need access only to some trivial
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OS specific functionality (e.g. query the CPU load), but need to configure and
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maintain separate build environments to do it.
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2014-08-13 12:09:53 +00:00
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## Enter xgo
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2014-08-07 07:05:33 +00:00
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My solution to the challenge of cross compiling Go code with embedded C snippets
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2014-08-07 07:09:32 +00:00
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(i.e. CGO_ENABLED=1) is based on the concept of [lightweight Linux containers](http://en.wikipedia.org/wiki/LXC).
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2014-08-07 07:05:33 +00:00
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All the necessary Go tool-chains, C cross compilers and platform headers/libraries
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have been assembled into a single Docker container, which can then be called as if
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2014-08-08 10:33:03 +00:00
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a single command to compile a Go package to various platforms and architectures.
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2014-08-07 07:05:33 +00:00
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2014-08-13 12:09:53 +00:00
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## Installation
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2014-08-07 07:05:33 +00:00
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Although you could build the container manually, it is available as an automatic
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2014-08-13 12:09:53 +00:00
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trusted build from Docker's container registry (~530MB):
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2014-08-07 07:05:33 +00:00
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2014-08-13 12:09:53 +00:00
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docker pull karalabe/xgo-latest
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2014-08-07 07:05:33 +00:00
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To prevent having to remember a potentially complex Docker command every time,
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a lightweight Go wrapper was written on top of it.
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2014-08-07 07:08:06 +00:00
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go get github.com/karalabe/xgo
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2014-08-07 07:05:33 +00:00
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2014-08-13 12:09:53 +00:00
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## Usage
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2014-08-07 07:05:33 +00:00
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Simply specify the import path you want to build, and xgo will do the rest:
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2014-08-07 07:08:06 +00:00
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$ xgo github.com/project-iris/iris
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2014-08-07 07:08:52 +00:00
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...
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2014-08-07 07:08:06 +00:00
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$ ls -al
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-rwxr-xr-x 1 root root 3086860 Aug 7 10:01 iris-darwin-386
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-rwxr-xr-x 1 root root 3941068 Aug 7 10:01 iris-darwin-amd64
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-rwxr-xr-x 1 root root 4185144 Aug 7 10:01 iris-linux-386
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-rwxr-xr-x 1 root root 5196784 Aug 7 10:01 iris-linux-amd64
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-rwxr-xr-x 1 root root 4151688 Aug 7 10:01 iris-linux-arm
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-rwxr-xr-x 1 root root 4228608 Aug 7 10:01 iris-windows-386.exe
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-rwxr-xr-x 1 root root 5243904 Aug 7 10:01 iris-windows-amd64.exe
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2014-08-13 12:09:53 +00:00
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### Go releases
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As newer versions of the language runtime, libraries and tools get released,
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these will get incorporated into xgo too as extensions layers to the base cross
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compilation image (only Go 1.3 and above will be supported).
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You can select which Go release to work with through the `-go` command line flag
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to xgo and if the specific release was already integrated, it will automatically
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be retrieved and installed.
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$ xgo -go 1.3.0 github.com/project-iris/iris
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...
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Since xgo depends on not only the official releases, but also on Dave Cheney's
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ARM packages, there will be a slight delay between official Go updates and the
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xgo updates.
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Additionally, a few wildcard release strings are also supported:
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- `-go latest` will use the latest Go release
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- `-go 1.3.x` will use the latest point release of a specific Go version
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