DLLCall()

[smashly]

Hi,

I've been poking around AutoIt UDF includes.

I notice that most the error checks after a DllCall have the @extended macro in the SetError() return.

eg:

$aResult = DllCall(xxxx, xxxx, xxxx, xxxx, xxxx)
If @error Then Return SetError(@error, @extended, 0)

I've looked through AutoIt help file and I can't see any mention of @extended returns when using DllCall()

I have tried making an error DllCall() and check what the @extended value is retuning and it's always 0 no matter what error type is returned.

So when error checking after a DllCall() what's the @extended meant to be for?

I'm mainly asking as I'm writing some gdiplus udf functions and it's sorta bugging me as i can't see the logic of it atm.

Am I missing something?

Cheers

Edited September 27, 2009 by smashly

[PsaltyDS]

Hi,

I've been poking around AutoIt UDF includes.

I notice that most the error checks after a DllCall have the @extended macro in the SetError() return.

eg:

$aResult = DllCall(xxxx, xxxx, xxxx, xxxx, xxxx)
If @error Then Return SetError(@error, @extended, 0)

I've looked through AutoIt help file and I can't see any mention of @extended returns when using DllCall()

I have tried making an error DllCall() and check what the @extended value is retuning and it's always 0 no matter what error type is returned.

So when error checking after a DllCall() what's the @extended meant to be for?

I'm mainly asking as I'm writing some gdiplus udf functions and it's sorta bugging me as i can't see the logic of it atm.

Am I missing something?

Cheers

DllCall() leaves @extended undefined.

The syntax of the SetError() function requires you to specify a value for @extended if you want to set the return value. In order to leave that value unchanged, you set @extended = @extended. It may not be significant in the case of functions using DllCall(), but is a good generic practice any way. The alternative is to destroy its previous value by something like SetError(@error, 0, 0).

[smashly]

Hi and Thank You for taking the time to explane.

Until you explained it I thought there might of been some undocumented @extended value returned by DllCall() on error that I was missing. lol

Yep my logic saw it as SetError(@error, 0, 0)

Cheers

[PsaltyDS]

Hi and Thank You for taking the time to explane.

Until you explained it I thought there might of been some undocumented @extended value returned by DllCall() on error that I was missing. lol

Yep my logic saw it as SetError(@error, 0, 0)

Cheers

I should have tested before spouting off. @error and @extended are both set to 0 when DllCall() or any function is called, and since DllCall() doesn't change @extended during execution, it remains zeroed out. Any value from previous to the DllCall() is gone.

In addition, SetExtended() and SetError() are themselves functions and any previous value not re-set in the parameters will be lost. Even Return will not leave the values of @error and @extended unless SetError() is used on the same line:

expandcollapse popup

For $n = 1 To 5
    $iRet = Call("_Test" & $n)
    ConsoleWrite($n & ":  $iRET = " & $iRet & ";  @error = " & @error & ";  @extended = " & @extended & @LF)
Next

Func _Test1()
    ; Returns @error, but previous @extended is lost on DllCall()
    SetExtended(-1)
    DllCall("NoneSuch.dll", "int", "NoSuchFunction") ; Generate an error
    Return SetError(@error, @extended, 1)
EndFunc   ;==>_Test1

Func _Test2()
    ; Both @error and @extended are lost on Return
    SetExtended(-1)
    DllCall("NoneSuch.dll", "int", "NoSuchFunction") ; Generate an error
    Return 2
EndFunc   ;==>_Test2

Func _Test3()
    ; Both @error and @extended are lost because there is no Return
    SetExtended(-1)
    DllCall("NoneSuch.dll", "int", "NoSuchFunction") ; Generate an error
EndFunc   ;==>_Test2

Func _Test4()
    ; @error is lost when SetExtended() is called
    SetError(-1)
    SetExtended(-2)
    Return 3
EndFunc   ;==>_Test3

Func _Test5()
    ; Returns both @error and @extended
    SetError(-1, -2)
    Return 4
EndFunc   ;==>_Test4

The safe bet is what was used:

Return SetError(@error, @extended, $iRetVal)

[smashly]

Hi,

Dang what did you go and do that for .. lol

I thought it made logical sense the first time round when you explained it..

Basically your tests were similar to what I tried before I originally posted.

My logic sees it as @extended is unneeded in the situation of:

$aResult = DllCall("xxxx", "xxx", xxxx","xxx","xxxx")

If @error Return SetEerror(@error, @extended, 0)

The reason it got my attention was due to I use at @extended to get a value return of a function that sets @extended data.

But if a function does not set @extended value and I'm Returning the SetError on the first line after a DllCall,

then @extended will always be 0 no matter what value @extended was before the DllCall().

So once again I really can't see the logic of why @extended has been used the way it was in the udfs when placed after a DllCall().

I mean it's not causing any problems or issues apart from to my logic ,

but I still couldn't see why @extended would be used as opposed to 0.

In the end against my logic telling me that 0 is visually shorter then @extended I opted to be a sheep and follow the the tried and proven way it's been done before.

After a DllCall() I use

If @error Return SetEerror(@error, @extended, "failure return value")

Once again thank you for taking the time to check it out.

It's appreciated.

Cheers