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WindowsCrossCompiling.md

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+# Building Windows Go programs on Linux
+
+See [here](https://go.dev/doc/install/source#environment) for available `GOOS` and `GOARCH` values.
+
+## Go version >= 1.5
+
+Since Go version 1.5 cross-compiling of pure Go executables has become very easy. Try it out with the code below. More can be found at this blog post by [Dave Cheney][1].
+
+[1]: http://dave.cheney.net/2015/08/22/cross-compilation-with-go-1-5
+
+```go
+$ cat hello.go
+package main
+
+import "fmt"
+
+func main() {
+        fmt.Printf("Hello\n")
+}
+$ GOOS=windows GOARCH=386 go build -o hello.exe hello.go
+```
+
+In cmd.exe instead of PowerShell:
+
+```go
+$ set GOOS=windows
+$ set GOARCH=386
+$ go build -o hello.exe hello.go
+```
+
+You can now run `hello.exe` on a Windows machine near you. 
+
+Note that the command above will silently rebuild most of standard library, and for this reason will be quite slow. To speed-up the process, you can install all the windows-amd64 standard packages on your system with
+
+```
+GOOS=windows GOARCH=amd64 go install
+```
+
+Note also that `cgo` is disabled when cross-compiling, so any file that mentions `import "C"` will be silently ignored (See https://github.com/golang/go/issues/24068).  In order to use cgo, or any of the build modes `c-archive`, `c-shared`, `shared`, `plugin`, you need to have a C cross-compiler.
+
+
+## Older Go version (<1.5)
+
+I use linux/386, but, I suspect, this procedure will apply to other host platforms as well.
+
+Preparation (if needed):
+```sh
+sudo apt-get install gcc
+export go env GOROOT
+```
+
+First step is to build host version of go:
+
+```sh
+cd $GOROOT/src
+sudo -E GOOS=windows GOARCH=386 PATH=$PATH ./make.bash
+```
+
+Next you need to build the rest of go compilers and linkers. I have small program to do that:
+
+```sh
+$ cat ~/bin/buildcmd
+#!/bin/sh
+set -e
+for arch in 8 6; do
+	for cmd in a c g l; do
+		go tool dist install -v cmd/$arch$cmd
+	done
+done
+exit 0
+```
+
+Last step is to build Windows versions of standard commands and libraries. I have a small script for that too:
+
+```sh
+$ cat ~/bin/buildpkg
+#!/bin/sh
+if [ -z "$1" ]; then
+	echo 'GOOS is not specified' 1>&2
+	exit 2
+else
+	export GOOS=$1
+	if [ "$GOOS" = "windows" ]; then
+		export CGO_ENABLED=0
+	fi
+fi
+shift
+if [ -n "$1" ]; then
+	export GOARCH=$1
+fi
+cd $GOROOT/src
+go tool dist install -v pkg/runtime
+go install -v -a std
+```
+
+I run it like that:
+
+```sh
+$ ~/bin/buildpkg windows 386
+```
+
+to build Windows/386 version of Go commands and packages. You can probably see from my script that I exclude building of any cgo related parts &mdash; these will not work for me, since I do not have correspondent gcc cross-compiling tools installed. So I just skip those.
+
+Now we're ready to build our Windows executable:
+
+```go
+$ cat hello.go
+package main
+
+import "fmt"
+
+func main() {
+        fmt.Printf("Hello\n")
+}
+$ GOOS=windows GOARCH=386 go build -o hello.exe hello.go
+```
+
+We just need to find a Windows computer to run our `hello.exe`.