Weird return from C++ dll

[JohnOne]

Getting an odd result from a DllCall.

I'd expect 65 as a result.

MsgBox(0,"Success", _Asc("A"))

Func _Asc($char)
    $a_Asc = DllCall("AU3.dll", "uint", "_Asc", "str", $char)
    If @error Then
        Exit MsgBox(0, "_Asc Error", @error)
    EndIf
    
    Return $a_Asc[0]
EndFunc

unsigned int __stdcall _Asc(char Char){

    return static_cast<unsigned int>(Char);
}

Instead I'm getting what appears to be random results such as 120, 4294967184 and others.

Can anyone give me a hint as to why this might be happening?

Win 7 32

VS 2010

Edited January 13, 2014 by JohnOne

[jaberwacky]

Only thing I see is that the c++ func expects a char but you call it a string in _Asc.

[JohnOne]

Yes, I'm not sure dllcall has a type char, well it errors out with 1 if  I use it with a data struct value, and if I use byte or int the return is 0.

[jaberwacky]

OK, my current research leads me to believe that the problem lies in the cast.  Maybe there is some sort of undefined compiler issue.

[JohnOne]

Possibly, cheers.

I've tried using a c style cast "(unsigned int)Char;" which is no good either.

[jaberwacky]

One possible solution I came across is this:

char a = "A";

unsigned int b = a;

return b;

[JohnOne]

I believe it's on autoit side.

this works fine.

unsigned int __stdcall _Asc(char Char){

    return static_cast<unsigned int>('A');
}

[Richard Robertson]

You can't mark the parameter as a string. Strings are sent via handles and not as literal data. The value you are printing is just one part of a handle.

Try using CHAR since that is valid in DllStructs. If that doesn't work, use BYTE and change the C function parameter type to unsigned char.

[trancexx]

When you say "wstr" or "str" it means string pointer. That means your dll func should accept just that:

unsigned int __stdcall _Asc(wchar_t* Char)
{

    // Sanity check
    if (Char == nullptr) return 0;

    // Read firts character
    wchar_t x = Char[0];
    
    // Return character value of your type
    return static_cast<unsigned int>(x);
}

And on script side:

MsgBox(0,"Success", _Asc("A"))

Func _Asc($char)
    $a_Asc = DllCall("AU3.dll", "uint", "_Asc", "wstr", $char)
    If @error Then
        Exit MsgBox(0, "_Asc Error", @error)
    EndIf

    Return $a_Asc[0]
EndFunc

[JohnOne]

Thanks trancex, I was so sure i was getting it wrong on AU3 side, I'd stopped looking on C side.

What is reason you recommend wstr over str?

[trancexx]

Of course you can use "str" if that suits your needs, only then you should adjust dll code to accept char* because the null terminator would be missing if you pass strings larger than one character and you would get results you don't expect.

[JohnOne]

I see, thank you very kindly ma'am.

[jchd]

Isn't it also that str is retricted to ANSI while wstr welcomes UTF-16?

[trancexx]

Yes, but maybe JohnOne is ANSI gay.

[JohnOne]

I'm everything the ladies want me to be, all kinds of gay too, if the price is right.

EDIT:

But I'll be honest, I do get mixed up with ANSI and ASCII all the time until I'm reminded.

Edited January 13, 2014 by JohnOne

[jchd]

You never know: maybe he's learning glagolitic.