fix backward comp call to shell32.SHGetFolderPathW

Author: cmaglie

shell32_windows.go

@@ -37,7 +37,7 @@ import (
 
 //sys getKnownFolderPath(rfid *syscall.GUID, dwFlags uint32, hToken syscall.Handle, path **uint16) (regerrno error) = shell32.SHGetKnownFolderPath
 //sys taskMemFree(pv uintptr) = ole32.CoTaskMemFree
-//sys getFolderPath(hwndOwner uint32, nFolder int, hToken syscall.Handle, dwFlags uint32, path *uint16) (err error) = shell32.SHGetFolderPathW
+//sys getFolderPath(hwndOwner uint32, nFolder int, hToken syscall.Handle, dwFlags uint32, path *uint16) (regerrno error) = shell32.SHGetFolderPathW
 
 func init() {
 	if err1, err2 := procSHGetKnownFolderPath.Find(), procCoTaskMemFree.Find(); err1 != nil || err2 != nil {

zshell32_windows.go

@@ -58,14 +58,10 @@ func taskMemFree(pv uintptr) {
 	return
 }
 
-func getFolderPath(hwndOwner uint32, nFolder int, hToken syscall.Handle, dwFlags uint32, path *uint16) (err error) {
-	r1, _, e1 := syscall.Syscall6(procSHGetFolderPathW.Addr(), 5, uintptr(hwndOwner), uintptr(nFolder), uintptr(hToken), uintptr(dwFlags), uintptr(unsafe.Pointer(path)), 0)
-	if r1 == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
+func getFolderPath(hwndOwner uint32, nFolder int, hToken syscall.Handle, dwFlags uint32, path *uint16) (regerrno error) {
+	r0, _, _ := syscall.Syscall6(procSHGetFolderPathW.Addr(), 5, uintptr(hwndOwner), uintptr(nFolder), uintptr(hToken), uintptr(dwFlags), uintptr(unsafe.Pointer(path)), 0)
+	if r0 != 0 {
+		regerrno = syscall.Errno(r0)
 	}
 	return
 }