Visual Basic, PLEASE HELP ! : Calling DLL in 32bit VB4.0

PLEASE HELP ! : Calling DLL in 32bit VB4.0

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Mark #1 / 4	PLEASE HELP ! : Calling DLL in 32bit VB4.0 --------------AFD3EE49CDC6055D6B7E70E5 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit I'm having problems calling a function in a C++ DLL. The DLL is found by the VB app, but gives an error ("Run-time error '453': Specified DLL function not found). This is how I have the DLL declared in the projects module file : Declare Function TestFunction Lib "test.dll" (ByVal word1 As String, ByVal word2 As String, ByVal word3 As String, ByVal word4 As String) And this is how I call the Function : returnVal = TestFunction(ByVal word1, ByVal word2, ByVal word3, ByVal word4) The DLL is built with Visual C++ version 4.1, and I have the source-code. The function takes 4 parameters - all pointers to strings. WHAT AM I DOING WRONG ??? Thanks in advance ! Mark. --------------AFD3EE49CDC6055D6B7E70E5 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit <HTML> I'm having problems calling a function in a C++ DLL. The DLL is found by the VB app, but gives an error ("Run-time error '453': Specified DLL function not found). This is how I have the DLL declared in the projects module file : <BR>? <P><B>Declare Function TestFunction Lib "test.dll" (ByVal word1 As String, ByVal word2 As String, ByVal word3 As String, ByVal word4 As String)</B> <P>And this is how I call the Function : <P><B>returnVal = TestFunction(ByVal word1, ByVal word2, ByVal word3, ByVal word4)</B><B></B> <P>The DLL is built with Visual C++ version 4.1, and I have the source-code. The function takes 4 parameters - all pointers to strings. <BR>? <P>WHAT AM I DOING WRONG ??? <BR>Thanks in advance ! <P>Mark. <BR>? <BR>?</HTML> --------------AFD3EE49CDC6055D6B7E70E5--
Mon, 01 May 2000 03:00:00 GMT

Jonna R?tt #2 / 4	PLEASE HELP ! : Calling DLL in 32bit VB4.0 This is a multi-part message in MIME format. ------=_NextPart_000_0044_01BCF0A1.58380B00 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Declare Function TestFunction Lib "test.dll" (ByVal word1 As String, = ByVal word2 As String, ByVal word3 As String, ByVal word4 As String)=20 =20 =20 =20 You need to use Alias, because you are dealing with string = variables. Try following: =20 Declare Function TestFunction Lib "test.dll" Alias "TestFunctionA" = ... =20 That should help you! =20 =20 =20 Thomas =20 =20 =20 ------=_NextPart_000_0044_01BCF0A1.58380B00 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type> <META content=3D'"MSHTML 4.71.1712.3"' name=3DGENERATOR> </HEAD> <BODY bgColor=3D#ffffff> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: = 5px"> <P><B>Declare Function TestFunction Lib "test.dll" (ByVal = word1 As=20 String, ByVal word2 As String, ByVal word3 As String, ByVal word4 As = String)</B>=20 <P>  <P><FONT color=3D#000000 size=3D2>You need to use Alias, because you = are dealing=20 with string variables. Try following:</FONT></P> <P><FONT color=3D#000000 size=3D2>Declare Function TestFunction Lib=20 "test.dll" Alias "TestFunctionA" ...</FONT></P> <P><FONT size=3D2>That should help you!</FONT></P> <P><FONT size=3D2></FONT> </P> <P><FONT size=3D2>Thomas</FONT></P> <P> </P></BLOCKQUOTE></BODY></HTML> ------=_NextPart_000_0044_01BCF0A1.58380B00--
Tue, 02 May 2000 03:00:00 GMT

Bart Late #3 / 4	PLEASE HELP ! : Calling DLL in 32bit VB4.0 Quote: >Declare Function TestFunction Lib "test.dll" (ByVal word1 As String, >ByVal word2 As String, ByVal word3 As String, ByVal word4 As String) >And this is how I call the Function : >returnVal = TestFunction(ByVal word1, ByVal word2, ByVal word3, ByVal >word4) Ah, don't do that: you're using Byval BOTH in the declaration and in the function call. Remove all Byval's from the function call. Second, does the function exist under that name? Try (in Win95) to right-click on the DLL-file, and see what name the function has been exported as. Probably it's NOT TestFunction. My bet is that the name has been mangled by VC. You'll have to declare the function properly in the EXPORTS section, but I'm not fluent enough with C to tell you exactly how this should be done. HTH, Bart.
Sat, 06 May 2000 03:00:00 GMT

Chuck Stase #4 / 4	PLEASE HELP ! : Calling DLL in 32bit VB4.0 Just a couple of things about this. I assume since you are passing them as byval that the procedure does not attempt to modify them so this is probably a mute argument. But if by some chance the procedure wants to modify any of the passed parameters then one thing you might want to do is predefine the word1, word2, word3 and word4 strings and fill them with blanks and pass them by reference. In this case Visual Basic passes an uninitialized string as a NULL and the DLL functions usually don't like this. Again, this is only if the dll wants to modify and return the parameter. Word1 = string(length," ") Another thing that Mark suggested is that the actual name of the procedure may not be what you think it is. I'm not sure just looking at the properties of the DLL is going to tell you the procedure names but there is something else you can do. If you have a hex editor you can load the DLL into it and search for what you believe to be the name of the function. When it finds it, note if it has any additional characters before or after the name and use the "ALIAS" keyword added to your declaration to call out the procedure name. Quote: > >Declare Function TestFunction Lib "test.dll" (ByVal word1 As String, > >ByVal word2 As String, ByVal word3 As String, ByVal word4 As String) > >And this is how I call the Function : > >returnVal = TestFunction(ByVal word1, ByVal word2, ByVal word3, ByVal > >word4) > Ah, don't do that: you're using Byval BOTH in the declaration and in the > function call. Remove all Byval's from the function call. > Second, does the function exist under that name? Try (in Win95) to > right-click on the DLL-file, and see what name the function has been > exported as. Probably it's NOT TestFunction. My bet is that the name has > been mangled by VC. You'll have to declare the function properly in the > EXPORTS section, but I'm not fluent enough with C to tell you exactly > how this should be done. > HTH, > Bart.
Sat, 06 May 2000 03:00:00 GMT

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