misc/cgo: prepare for 64-bit ints

In a few places, the existing cgo tests assume that a
Go int is the same as a C int. Making int 64 bits wide
on 64-bit platforms violates this assumption.
Change that code to assume that Go int32 and C int
are the same instead. That's still not great, but it's better,
and I am unaware of any systems we run on where it is not true.

Update #2188.

R=iant, r
CC=golang-dev
https://golang.org/cl/6552064

misc/cgo/life/life.go

@@ -11,8 +11,8 @@ import "C"
 
 import "unsafe"
 
-func Run(gen, x, y int, a []int) {
-	n := make([]int, x*y)
+func Run(gen, x, y int, a []int32) {
+	n := make([]int32, x*y)
 	for i := 0; i < gen; i++ {
 		C.Step(C.int(x), C.int(y), (*C.int)(unsafe.Pointer(&a[0])), (*C.int)(unsafe.Pointer(&n[0])))
 		copy(a, n)

misc/cgo/life/main.go

@@ -24,7 +24,7 @@ var gen = flag.Int("gen", 10, "generations")
 func main() {
 	flag.Parse()
 
-	var a [MAXDIM * MAXDIM]int
+	var a [MAXDIM * MAXDIM]int32
 	for i := 2; i < *dim; i += 8 {
 		for j := 2; j < *dim-3; j += 8 {
 			for y := 0; y < 3; y++ {

misc/cgo/test/issue1560.go

@@ -28,7 +28,7 @@ func parallelSleep(n int) {
 }
 
 //export BackgroundSleep
-func BackgroundSleep(n int) {
+func BackgroundSleep(n int32) {
 	go func() {
 		C.sleep(C.uint(n))
 		sleepDone <- true