This function verifies that the calling process has write access to the specified range of memory.
Zero indicates that the calling process has write access to all bytes in the specified memory range. Nonzero indicates that the calling process does not have write access to all bytes in the specified memory range.
If the application is compiled as a debugging version and the process does not have write access to all bytes in the specified memory range, the function causes an assertion and breaks into the debugger. Leaving the debugger, the function continues as usual and returns a nonzero value. This behavior is by design, as a debugging aid.
If the calling process has write access to some, but not all, of the bytes in the specified memory range, the return value is nonzero.
When running in kernel mode, any pointer over 0x80000000 is returned as valid.
In a pre-emptive multitasking environment, another thread could change the access of the process to the memory being tested.
Even when the function indicates that the process has write access to the specified memory, use structured exception handling when attempting to access the memory.
Use of structured exception handling enables the system to notify the process if an access violation exception occurs, giving the process an opportunity to handle the exception.
This function is unsafe to use when checking your input parameters for correctness or accuracy. For more information about secure coding practices, see Security for Windows Mobile Devices.