syscall: keep Windows syscall pointers live too

Like https://golang.org/cl/139360044

LGTM=rsc, alex.brainman
R=alex.brainman, rsc
CC=golang-codereviews
https://golang.org/cl/138250043

src/syscall/mksyscall_windows.go

@@ -158,6 +158,7 @@ func (p *Param) SyscallArgList() []string {
 	case p.Type[0] == '*':
 		s = fmt.Sprintf("unsafe.Pointer(%s)", p.Name)
 	case p.Type == "string":
+		p.fn.use(p.tmpVar())
 		s = fmt.Sprintf("unsafe.Pointer(%s)", p.tmpVar())
 	case p.Type == "bool":
 		s = p.tmpVar()
@@ -303,6 +304,7 @@ type Fn struct {
 	Params      []*Param
 	Rets        *Rets
 	PrintTrace  bool
+	Used        []string
 	dllname     string
 	dllfuncname string
 	src         string
@@ -310,6 +312,15 @@ type Fn struct {
 	curTmpVarIdx int // insure tmp variables have uniq names
 }
 
+func (f *Fn) use(v string) {
+	for _, e := range f.Used {
+		if e == v {
+			return
+		}
+	}
+	f.Used = append(f.Used, v)
+}
+
 // extractParams parses s to extract function parameters.
 func extractParams(s string, f *Fn) ([]*Param, error) {
 	s = trim(s)
@@ -328,7 +339,7 @@ func extractParams(s string, f *Fn) ([]*Param, error) {
 			}
 		}
 		ps[i] = &Param{
-			Name:      trim(b[0]),
+			Name:      sanitizeName(trim(b[0])),
 			Type:      trim(b[1]),
 			fn:        f,
 			tmpVarIdx: -1,
@@ -337,6 +348,13 @@ func extractParams(s string, f *Fn) ([]*Param, error) {
 	return ps, nil
 }
 
+func sanitizeName(n string) string {
+	if n == "use" {
+		return "use_"
+	}
+	return n
+}
+
 // extractSection extracts text out of string s starting after start
 // and ending just before end. found return value will indicate success,
 // and prefix, body and suffix will contain correspondent parts of string s.
@@ -680,7 +698,7 @@ var (
 {{define "funcbody"}}
 func {{.Name}}({{.ParamList}}) {{if .Rets.List}}{{.Rets.List}} {{end}}{
 {{template "tmpvars" .}}	{{template "syscall" .}}
-{{template "seterror" .}}{{template "printtrace" .}}	return
+{{template "used" .}}{{template "seterror" .}}{{template "printtrace" .}}	return
 }
 {{end}}
 
@@ -689,6 +707,8 @@ func {{.Name}}({{.ParamList}}) {{if .Rets.List}}{{.Rets.List}} {{end}}{
 
 {{define "syscall"}}{{.Rets.SetReturnValuesCode}}{{.Syscall}}(proc{{.DLLFuncName}}.Addr(), {{.ParamCount}}, {{.SyscallParamList}}){{end}}
 
+{{define "used"}}{{range .Used}}use(unsafe.Pointer({{.}}));{{end}}{{end}}
+
 {{define "seterror"}}{{if .Rets.SetErrorCode}}	{{.Rets.SetErrorCode}}
 {{end}}{{end}}
 

src/syscall/zsyscall_windows.go

@@ -177,6 +177,7 @@ func LoadLibrary(libname string) (handle Handle, err error) {
 		return
 	}
 	r0, _, e1 := Syscall(procLoadLibraryW.Addr(), 1, uintptr(unsafe.Pointer(_p0)), 0, 0)
+	use(unsafe.Pointer(_p0))
 	handle = Handle(r0)
 	if handle == 0 {
 		if e1 != 0 {
@@ -207,6 +208,7 @@ func GetProcAddress(module Handle, procname string) (proc uintptr, err error) {
 		return
 	}
 	r0, _, e1 := Syscall(procGetProcAddress.Addr(), 2, uintptr(module), uintptr(unsafe.Pointer(_p0)), 0)
+	use(unsafe.Pointer(_p0))
 	proc = uintptr(r0)
 	if proc == 0 {
 		if e1 != 0 {
@@ -1559,6 +1561,7 @@ func GetHostByName(name string) (h *Hostent, err error) {
 		return
 	}
 	r0, _, e1 := Syscall(procgethostbyname.Addr(), 1, uintptr(unsafe.Pointer(_p0)), 0, 0)
+	use(unsafe.Pointer(_p0))
 	h = (*Hostent)(unsafe.Pointer(r0))
 	if h == nil {
 		if e1 != 0 {
@@ -1582,6 +1585,8 @@ func GetServByName(name string, proto string) (s *Servent, err error) {
 		return
 	}
 	r0, _, e1 := Syscall(procgetservbyname.Addr(), 2, uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(_p1)), 0)
+	use(unsafe.Pointer(_p0))
+	use(unsafe.Pointer(_p1))
 	s = (*Servent)(unsafe.Pointer(r0))
 	if s == nil {
 		if e1 != 0 {
@@ -1606,6 +1611,7 @@ func GetProtoByName(name string) (p *Protoent, err error) {
 		return
 	}
 	r0, _, e1 := Syscall(procgetprotobyname.Addr(), 1, uintptr(unsafe.Pointer(_p0)), 0, 0)
+	use(unsafe.Pointer(_p0))
 	p = (*Protoent)(unsafe.Pointer(r0))
 	if p == nil {
 		if e1 != 0 {
@@ -1624,6 +1630,7 @@ func DnsQuery(name string, qtype uint16, options uint32, extra *byte, qrs **DNSR
 		return
 	}
 	r0, _, _ := Syscall6(procDnsQuery_W.Addr(), 6, uintptr(unsafe.Pointer(_p0)), uintptr(qtype), uintptr(options), uintptr(unsafe.Pointer(extra)), uintptr(unsafe.Pointer(qrs)), uintptr(unsafe.Pointer(pr)))
+	use(unsafe.Pointer(_p0))
 	if r0 != 0 {
 		status = Errno(r0)
 	}
@@ -1743,8 +1750,8 @@ func NetApiBufferFree(buf *byte) (neterr error) {
 	return
 }
 
-func LookupAccountSid(systemName *uint16, sid *SID, name *uint16, nameLen *uint32, refdDomainName *uint16, refdDomainNameLen *uint32, use *uint32) (err error) {
-	r1, _, e1 := Syscall9(procLookupAccountSidW.Addr(), 7, uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(sid)), uintptr(unsafe.Pointer(name)), uintptr(unsafe.Pointer(nameLen)), uintptr(unsafe.Pointer(refdDomainName)), uintptr(unsafe.Pointer(refdDomainNameLen)), uintptr(unsafe.Pointer(use)), 0, 0)
+func LookupAccountSid(systemName *uint16, sid *SID, name *uint16, nameLen *uint32, refdDomainName *uint16, refdDomainNameLen *uint32, use_ *uint32) (err error) {
+	r1, _, e1 := Syscall9(procLookupAccountSidW.Addr(), 7, uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(sid)), uintptr(unsafe.Pointer(name)), uintptr(unsafe.Pointer(nameLen)), uintptr(unsafe.Pointer(refdDomainName)), uintptr(unsafe.Pointer(refdDomainNameLen)), uintptr(unsafe.Pointer(use_)), 0, 0)
 	if r1 == 0 {
 		if e1 != 0 {
 			err = error(e1)
@@ -1755,8 +1762,8 @@ func LookupAccountSid(systemName *uint16, sid *SID, name *uint16, nameLen *uint3
 	return
 }
 
-func LookupAccountName(systemName *uint16, accountName *uint16, sid *SID, sidLen *uint32, refdDomainName *uint16, refdDomainNameLen *uint32, use *uint32) (err error) {
-	r1, _, e1 := Syscall9(procLookupAccountNameW.Addr(), 7, uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(accountName)), uintptr(unsafe.Pointer(sid)), uintptr(unsafe.Pointer(sidLen)), uintptr(unsafe.Pointer(refdDomainName)), uintptr(unsafe.Pointer(refdDomainNameLen)), uintptr(unsafe.Pointer(use)), 0, 0)
+func LookupAccountName(systemName *uint16, accountName *uint16, sid *SID, sidLen *uint32, refdDomainName *uint16, refdDomainNameLen *uint32, use_ *uint32) (err error) {
+	r1, _, e1 := Syscall9(procLookupAccountNameW.Addr(), 7, uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(accountName)), uintptr(unsafe.Pointer(sid)), uintptr(unsafe.Pointer(sidLen)), uintptr(unsafe.Pointer(refdDomainName)), uintptr(unsafe.Pointer(refdDomainNameLen)), uintptr(unsafe.Pointer(use_)), 0, 0)
 	if r1 == 0 {
 		if e1 != 0 {
 			err = error(e1)