Cross-compile Go platform

examples/GoPlatform/.gitignore

@@ -1,5 +1,11 @@
-platform/libapp.so
-platform/dynhost
-platform/*.rh
-platform/*.rm
+host/libapp.so
+host/dynhost
+host/*.rh
+host/*.rm
+host/libhost*
+
+platform/*.a
+
 *.tar.br
+
+build

examples/GoPlatform/build.roc

@@ -0,0 +1,51 @@
+app "build-platform-prebuilt-binaries"
+    packages {
+        cli: "../../../basic-cli/platform/main.roc",
+    }
+    imports [
+        cli.Stdout,
+        cli.Cmd,
+        cli.Task.{ Task },
+    ]
+    provides [main] to cli
+
+SupportedTarget : [
+    MacosArm64,
+    MacosX64,
+    LinuxArm64,
+    LinuxX64,
+    WindowsArm64,
+    WindowsX64,
+]
+
+main =
+
+    buildGoTarget! MacosArm64
+
+    # TODO -- why is this failing with "build constraints exclude all Go files"?
+    buildGoTarget! MacosX64 
+
+    # buildGoTarget! LinuxArm64
+    # etc
+
+    Stdout.line "DONE"
+
+buildGoTarget : SupportedTarget -> Task {} _
+buildGoTarget = \target -> 
+
+    (goos, goarch, prebuiltBinary) = when target is
+        MacosArm64 -> ("darwin", "arm64", "macos-arm64.a")
+        MacosX64 -> ("darwin", "amd64", "macos-x64")
+        LinuxArm64 -> ("linux", "arm64", "linux-arm64.a")
+        LinuxX64 -> ("linux", "amd64", "linux-x64.a")
+        WindowsArm64 -> ("windows", "arm64", "windows-arm64.a")
+        WindowsX64 -> ("windows", "amd64", "windows-x64")
+
+    Cmd.new "go"
+    |> Cmd.envs [("GOOS", goos), ("GOARCH", goarch)]
+    |> Cmd.args ["build", "-C", "host", "-buildmode=c-archive", "-o","libhost.a"]
+    |> Cmd.status
+    |> Task.mapErr! \err -> BuildErr goos goarch (Inspect.toStr err)
+
+    Cmd.exec "cp" ["host/libhost.a", "platform/$(prebuiltBinary)"]
+    |> Task.mapErr! \err -> CpErr (Inspect.toStr err)

examples/GoPlatform/build.sh

@@ -0,0 +1,4 @@
+GOOS=linux GOARCH=arm64 go build -C host -buildmode=c-archive -o libhost.a
+cp host/libhost.a platform/macos-arm64.a
+
+roc dev --prebuilt-platform main.roc

examples/GoPlatform/host/go.mod

@@ -0,0 +1,3 @@
+module host
+
+go 1.23

examples/GoPlatform/platform/main.go → examples/GoPlatform/host/host.go

@@ -1,7 +1,7 @@
 package main
 
 /*
-#cgo LDFLAGS: -L. -lapp
+#cgo CFLAGS: -Wno-main-return-type
 #include "./host.h"
 */
 import "C"
@@ -12,6 +12,7 @@ import (
 	"unsafe"
 )
 
+//export main
 func main() {
 	var str C.struct_RocStr
 	C.roc__mainForHost_1_exposed_generic(&str)