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Post by Walt Decker on Dec 5, 2020 16:42:48 GMT -5
Definition of the function:
SUB TestLb ALIAS "TestLb"(BYVAL Varb_0 AS DWORD, BYVAL Varb_2 AS DWORD) EXPORT
The following passes incorrect value to Varb_2
OPEN "E:\PBwin10\DLLS\DbFetch.dll" for DLL as #Fetch
RetVal = 0
Varb.0 = 1
Varb.1 = 2
CALLDLL #Fetch, "TestLb", Varb.0 AS long, Varb.1 AS long, RetVal as LONG
CLOSE #Fetch
PRINT Varb.0, Varb.1, RetVal
Retval comes back as 1 when it should be 0
If I eliminate the RetVal reference, then Varb.0 = 1, Varb.1 = 1 and RetVal = 0
wait
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Post by Chris Iverson on Dec 5, 2020 17:22:35 GMT -5
If I'm reading that definition correctly, TestLb is a sub. It doesn't return anything. You declared in LB that it does return a value, and are surprised when you get garbage back.
Garbage in, garbage out; if you get the calling convention wrong, you'll get meaningless results.
If you're calling a function that doesn't return a value, you should declare it in LB as "void".
That is, in LB, you always need to have a final parameter specified as the return value, otherwise, it'll think one of your other parameters is supposed to hold the return value.
"Retval as void" should do what you need.
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Post by Walt Decker on Dec 6, 2020 10:14:14 GMT -5
Ah, "VOID." That should take care of that problem.
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Post by Walt Decker on Dec 17, 2020 12:06:53 GMT -5
Given:
STRUCT tH, _
MainDlg AS ULONG, _
TxtCtl AS ULONG, _
TxtId AS ULONG, _
OrigCB AS ULONG
MainHndl = 0
TxtHndl = 0
C = 0
NOMAINWIN
WinLeftX = 300
WinLeftY = 100
WindowWidth = 300
WindowHeight = 200
TEXTEDITOR #Win.Txt, 0, 0, 300, 200
OPEN "Edit Test" FOR WINDOW AS #Win
tH.MainDlg.struct = HWND(#Win)
tH.TxtCtl.struct = HWND(#Win.Txt)
MainHndl = tH.MainDlg.struct
TxtHndl = tH.TxtCtl.struct
OPEN "User32" FOR DLL AS #USER
CALLDLL #USER, "GetDlgCtrlID", TxtHndl AS ULONG, tH.TxtCtl.struct AS ULONG
PRINT #Win.Txt, tH.TxtCtl.struct
CALLDLL #USER, "GetDlgCtrlID", TxtHndl AS ULONG, C AS ULONG
PRINT #Win.Txt, C
WAIT
CLOSE #Win
CLOSE #USER
END
"GetDlgCtrlID" returns the ID number of a control.
On return "tH.TxtCtl.struct" contains some off the wall number (possibly a pointer) whereas the same call with "C" as a return variable contains a proper control ID.
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Post by Brandon Parker on Dec 20, 2020 20:29:25 GMT -5
First, you should use a temporary value for your return from the "GetDlgCtrlID" function and then assign that to a structure member. Also, did you not want to assign the return value to tH.TxtId.struct?
Second, the return type for the "GetDlgCtrlID" function is Int according to MSDN; in LB one would normally use a Long data type for an Int. Handle variables should be Ulong always.
When I do that I get 101 as the return value.
STRUCT tH, _
MainDlg AS ULONG, _
TxtCtl AS ULONG, _
TxtId AS LONG, _
OrigCB AS LONG
MainHndl = 0
TxtHndl = 0
C = 0
NOMAINWIN
WinLeftX = 300
WinLeftY = 100
WindowWidth = 300
WindowHeight = 200
TEXTEDITOR #Win.Txt, 0, 0, 300, 200
OPEN "Edit Test" FOR WINDOW AS #Win
tH.MainDlg.struct = HWND(#Win)
tH.TxtCtl.struct = HWND(#Win.Txt)
MainHndl = tH.MainDlg.struct
TxtHndl = tH.TxtCtl.struct
OPEN "User32" FOR DLL AS #USER
CALLDLL #USER, "GetDlgCtrlID", TxtHndl AS ULONG, TxtCtl AS LONG
tH.TxtId.struct = TxtCtl
PRINT #Win.Txt, tH.TxtId.struct
CALLDLL #USER, "GetDlgCtrlID", TxtHndl AS ULONG, C AS LONG
PRINT #Win.Txt, C
Wait
CLOSE #Win
CLOSE #USER
END
{:0)
Brandon Parker
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