DllCall to my dll function returning structure is not working.

[IndianSage 0]

I have create a function in FreeBasic like below:

Extern "Windows-MS"

    Type tA
        f1 As Integer
        f2 As Integer
    End Type

    Public Function _switchOrder(ByVal no1 As Integer, ByVal no2 As Integer) As tA Export
        Dim result As Integer

        Dim taa As  tA  

        taa.f1 = no2

        taa.f2 = no1

        Return taa

    End Function

End Extern

Caller AutoIt code is:

#include <MsgBoxConstants.au3>

Global Const $sTag_ftdi_version_info="struct; int no1a; int no2a; endstruct"

Local $aRet=DllCall("Math1.dll","Ptr","_switchOrder", "Int", 10, "Int", 30)
;MsgBox (0,"",@error & "-" & $aRet[0] & "-" & $aRet[1]& "-" & $aRet[2])

Local $t_ftdi_version_info=DllStructCreate($sTag_ftdi_version_info,$aRet[0])
MsgBox (0,"msg1=",@error & "---" & $aRet[0] & "-" & $aRet[1]& "-" & $aRet[2])

;Local $retData1 = DllStructGetData($t_ftdi_version_info,"",1)
Local $retData1 = DllStructGetData($t_ftdi_version_info,"no1a")
MsgBox (0,"msg2=",@error & "--" & $retData1)

;Local $retData1 = DllStructGetData($t_ftdi_version_info,"",2)
Local $retData1 = DllStructGetData($t_ftdi_version_info,"no2a")
MsgBox (0,"msg2=",@error & "--" & $retData1)

;ConsoleWrite(DllStructGetData($t_ftdi_version_info,"",2) & "--" & @error)
;ConsoleWrite(DllStructGetData($t_ftdi_version_info,"no2a") & @CRLF)
;ConsoleWrite(DllStructGetData($tversion_str,1) & @CRLF)

Getting error 2 for DllStructGetData or it give Close Application AutoIt popup message. 

Certainly DllCall is not returning pointer to the Structure in $aRet[0] hence issue.

Can someone help me fix this please?

Thanks in advance.

 

 

[JLogan3o13 1,726]

Moved to the correct forum, as the Technical Discussion form very clearly states "DO not post general support questions here"

[IndianSage 0]

Mr. JLogan,

Just be clear, was my this question supposed to be in General Support category?

Thanks for bearing with me till I get to understand the categories clearly.

[Danp2 1,258]

Have you checked the size of the structure in FreeBasic and Autoit to ensure they match?

[Danyfirex 785]

Hello I'm not a freebasic programmer but I think your structure will be free when the function ends. probably you need to use a global structure. I'm not sure if freebasic provide structure pointer or need to use a function like strptr or varptr like old vb6 or something like @Mystructure.  I think is not a good practices to return an structure from a library.  the correct way should be that you pass your structure's pointer an be filled/modify inside the library.

 

Saludos

[jguinch 459]

It seems @Danyfirex is right.

After some tests, it seems this one works :

Extern "Windows-MS"
    Type tA
        f1 As Integer
        f2 As Integer
    End Type
    
    Public Function addition(no1  As Integer, no2  As Integer, Byref v As tA Ptr) As Integer Export
        Dim o As tA
        Dim s As Integer
        o.f1 = no2
        o.f2 = no1
        *v = o
        Return 0
    End Function

End Extern

Local $ptr = DllStructCreate("int f1;int f2")

$aRet = DllCall('test.dll', 'int', 'addition', 'int', 10, 'int', 30, 'ptr*', DllStructGetPtr($ptr) )
ConsoleWrite( "F1=" & DllStructGetData($ptr, 'f1') & @LF & _
              "F2=" & DllStructGetData($ptr, 'f2') & @LF )

 

Edited February 14, 2020 by jguinch

[Danp2 1,258]

I wonder if the code in the OP would work if you removed the "struct endstruct" from the DllStructCreate.

[jguinch 459]

21 hours ago, Danp2 said:

I wonder if the code in the OP would work if you removed the "struct endstruct" from the DllStructCreate.

No, it did not work (I just tried)

 

[IndianSage 0]

By the way I tried with Array too using ClassLibrary using Vb.net and C# both but it does not work. The other functions with VB.Net and C# returning Integers etc. worked fine.

I will try now with ByRef Array and modify them in ClassLibrary function as suggested by DanyFirex above and see if I get the data back. 

If it works fine my main purpose of returning multiple large number of items from classlibrary function is solved then in that case. 

I will revert after trying it out. Thanks in the meanwhile.