DllCall - CallBack

[MadaraUchiha]

Hi,

I am currently learning how to use DLLCalls etc.

So I made my first script, using the help files instructions etc:

Local $dwFreq = 600
Local $dwDuration = 1500
Local $DLL_BEEP = DllCall("kernel32.dll","BOOLEAN","Beep",'UINT',$dwFreq,'UINT',$dwDuration)

This works perfectly fine, but I checked PInvoke and MSDN, and it says it has a return type (Boolean in this case)

How can I get the return type, if it succeeded or not, and if not, why? Using GetLastError or something similar?

[MadaraUchiha]

And also...

If I try it like this:

Func SYS_BEEP($dwFreq,$dwDuration)
    Global $BEEP_Return = DllCall("kernel32.dll","BOOLEAN","Beep",'UINT',$dwFreq,'UINT',$dwDuration)
EndFunc

SYS_BEEP(343,500)

MsgBox(0,'Result','DllCall Result was:  ' & $BEEP_Return[0])

It returns me 1 (true?); - even if I set garbage as parameters like letters instead of numbers for the duration.

It still returns 1??

[kylomas]

MU,

Run it like this and look at DLLCALL in the Help file...

#include <array.au3>

Local $dwFreq = 600
Local $dwDuration = 1500
Local $DLL_BEEP = DllCall("kernel32.dll","BOOLEAN","Beep",'UINT',$dwFreq,'UINT',$dwDuration)

_arraydisplay($DLL_BEEP)

kylomas

edit: Feed the call garbage and look at the parms when the callreturns

Edited November 7, 2013 by kylomas

[MadaraUchiha]

If i change for example the durations param to some garbage, it returns 0 for duration, but main result, $Result[0] is still 1?

[kylomas]

Yes, I see what you mean.  Tried feeding it

-1

string($dwFreq) with $dwFreq = 'a'

chr($dwFreq)

and none of that makes the function fail...?

Maybe someone else has an idea...

kylomas

[MadaraUchiha]

Hm, okay, the problem is still unsolved...

[trancexx]

There are no problems here.

[kylomas]

trancexx,

Are you saying that DLLCALL concerts whatever you feed it into a dWord, consequently the call never fails (keeping in mind that 0 is a valid value)?

[trancexx]

If that word is "converts" then yes. Whatever you pass as argument is converted to specified type before the actual call happens.