Several Windows Embedded CE API's deal with handles: an application obtains a handle to an object than it typically checks if the handle is valid or not; unfortunately there are two values which means invalid handle: for example CreateFile returns INVALID_HANDLE_VALUE (which is defined as -1 or 0xFFFFFFFF) while CreateEvent returns NULL.
A mnemonic aid is the following: all the API's that deal with files, storage and database (CreateFile, FindFirstChangeNotification, OpenStore, CeOpenDatabaseEx, ...) return INVALID_HANDLE_VALUE while the other API's return NULL.
Some noticeable exceptions to this statement are:
-
CreateToolhelp32Snapshot
-
FindFirstDevice
-
CeFindFirstRegChange
which returns INVALID_HANDLE_VALUE.
Note that there is an error in Windows Embedded CE documentation about OpenDeviceKey: it is stated that the function returns INVALID_HANDLE_VALUE in case of error while it actually returns NULL.