runtime: refactor initialization code

Let each target handle its own initialization/finalization sequence
instead of providing one in the runtime with hooks for memory
initialization etc. This is much more flexible although it causes a
little bit of code duplication.

src/runtime/runtime.go

@@ -23,25 +23,6 @@ func initAll()
 //     scheduler(coroutine)
 func mainWrapper()
 
-// Entry point for Go. Initialize all packages and call main.main().
-//go:export main
-func main() int {
-	// Initialize memory etc.
-	preinit()
-
-	// Run initializers of all packages.
-	initAll()
-
-	// Enable interrupts etc.
-	postinit()
-
-	// Compiler-generated wrapper to main.main().
-	mainWrapper()
-
-	// For libc compatibility.
-	return 0
-}
-
 func GOMAXPROCS(n int) int {
 	// Note: setting GOMAXPROCS is ignored.
 	return 1

src/runtime/runtime_arm.go

@@ -40,9 +40,6 @@ func preinit() {
 	}
 }
 
-func postinit() {
-}
-
 func abort() {
 	for {
 		arm.Asm("wfi")

src/runtime/runtime_avr.go

@@ -36,6 +36,15 @@ var _sbss unsafe.Pointer
 //go:extern _ebss
 var _ebss unsafe.Pointer
 
+//go:export main
+func main() {
+	preinit()
+	initAll()
+	postinit()
+	mainWrapper()
+	abort()
+}
+
 func preinit() {
 	// Initialize .bss: zero-initialized global variables.
 	ptr := uintptr(unsafe.Pointer(&_sbss))
@@ -107,7 +116,6 @@ func ticks() timeUnit {
 }
 
 func abort() {
-	avr.Asm("cli")
 	for {
 		sleepWDT(WDT_PERIOD_2S)
 	}

src/runtime/runtime_nrf.go

@@ -16,9 +16,12 @@ const tickMicros = 1024 * 32
 func systemInit()
 
 //go:export Reset_Handler
-func handleReset() {
+func main() {
 	systemInit()
-	main()
+	preinit()
+	initAll()
+	mainWrapper()
+	abort()
 }
 
 func init() {

src/runtime/runtime_stm32.go

@@ -11,11 +11,11 @@ type timeUnit int64
 const tickMicros = 1 // TODO
 
 //go:export Reset_Handler
-func handleReset() {
-	main()
-}
-
-func init() {
+func main() {
+	preinit()
+	initAll()
+	mainWrapper()
+	abort()
 }
 
 func putchar(c byte) {

src/runtime/runtime_unix.go

@@ -24,10 +24,17 @@ type timespec struct {
 
 const CLOCK_MONOTONIC_RAW = 4
 
-func preinit() {
-}
+// Entry point for Go. Initialize all packages and call main.main().
+//go:export main
+func main() int {
+	// Run initializers of all packages.
+	initAll()
+
+	// Compiler-generated wrapper to main.main().
+	mainWrapper()
 
-func postinit() {
+	// For libc compatibility.
+	return 0
 }
 
 func putchar(c byte) {