C++ dll param Handling

[JohnOne]

I have an exported C++ win32 dll function.
It has 2 parameters of LPTSTR.
It works as I expect when I give it correct params.

If I pass an empty string however ("wstr", ""), it errors out with...

ERROR_INVALID_PARAMETER

87 (0x57)

The parameter is incorrect.

 

I tried to handle it like so...

if (!param || param == L"") {
        CloseHandle(hndl);
        return 0;
}

But it does not seem to catch that and the function proceeds, and of course errors out.

I guess it's because there's nothing there to have a pointer to, but my question is, is there way to correctly handle this.

Cheers for reading, and I hope I made sense.

EDIT:

I figured an unsafe way to deal with the param that's expecting a fully qualified path, by testing for ":"

Of course that's just silly.

Edited February 17, 2014 by JohnOne

[Richard Robertson]

Equality of strings will check for the pointers being equal. What you actually want with C strings (character arrays) when checking for null or empty is this.

if (!param || !*param)

This will check to see if the pointer is null, and if it isn't, checks to see if the first character pointed to is null.

If it's supposed to be a path, you should probably validate it using this http://msdn.microsoft.com/en-us/library/windows/desktop/bb773584%28v=vs.85%29.aspx

Edited February 17, 2014 by Richard Robertson

[JohnOne]

So simple, I cannot believe I never thought of that.

Thank you Richard.