starlark: use syscall.Mmap to avoid golang.org/x/sys dependency (goog…

…le#287)

Also, enable the optimization on other POSIX platforms.

go.mod

@@ -6,5 +6,5 @@ require (
 	github.com/chzyer/logex v1.1.10 // indirect
 	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e
 	github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 // indirect
-	golang.org/x/sys v0.0.0-20191002063906-3421d5a6bb1c
+	golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae // indirect
 )

go.sum

@@ -4,5 +4,5 @@ github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e h1:fY5BOSpyZCqRo5O
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 h1:q763qf9huN11kDQavWsoZXJNW3xEE4JJyHa5Q25/sd8=
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
-golang.org/x/sys v0.0.0-20191002063906-3421d5a6bb1c h1:Vco5b+cuG5NNfORVxZy6bYZQ7rsigisU1WQFkvQ0L5E=
-golang.org/x/sys v0.0.0-20191002063906-3421d5a6bb1c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae h1:Ih9Yo4hSPImZOpfGuA4bR/ORKTAbhZo2AbWNRCnevdo=
+golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

starlark/int_generic.go

@@ -1,4 +1,4 @@
-//+build !linux,!darwin darwin,arm64 !amd64,!arm64,!mips64x,!ppc64x
+//+build !linux,!darwin,!dragonfly,!freebsd,!netbsd,!openbsd,!solaris darwin,arm64 !amd64,!arm64,!mips64x,!ppc64x
 
 package starlark
 

starlark/int_posix64.go

@@ -1,4 +1,4 @@
-//+build linux darwin
+//+build linux darwin dragonfly freebsd netbsd openbsd solaris
 //+build amd64 arm64,!darwin mips64x ppc64x
 
 package starlark
@@ -22,9 +22,9 @@ import (
 	"log"
 	"math"
 	"math/big"
+	"runtime"
+	"syscall"
 	"unsafe"
-
-	"golang.org/x/sys/unix"
 )
 
 // intImpl represents a union of (int32, *big.Int) in a single pointer,
@@ -59,7 +59,15 @@ func makeBigInt(x *big.Int) Int { return Int{intImpl(x)} }
 var smallints = reserveAddresses(1 << 32)
 
 func reserveAddresses(len int) uintptr {
-	b, err := unix.Mmap(-1, 0, len, unix.PROT_READ, unix.MAP_PRIVATE|unix.MAP_ANONYMOUS)
+	// Use syscall to avoid golang.org/x/sys/unix dependency.
+	MAP_ANON := 0x1000 // darwin (and all BSDs)
+	switch runtime.GOOS {
+	case "linux":
+		MAP_ANON = 0x20
+	case "solaris":
+		MAP_ANON = 0x100
+	}
+	b, err := syscall.Mmap(-1, 0, len, syscall.PROT_READ, syscall.MAP_PRIVATE|MAP_ANON)
 	if err != nil {
 		log.Fatalf("mmap: %v", err)
 	}