VC++ DLL in VB

[ss2905]

Hi,
I have a VB app that needs to call a function written in VC++.The VB app passes an int and the function returns a LPSTR.
e.g VB passes 1 to the function which returns "st".Similarly, for 2, "nd" is returned,etc..that The function works fine but problem is it returns junk char after the string.So, I am not able to append any strings to this variable in VB.
eg.Instead of "2nd day" I am getting only "2nd".I'm padding up the LPSTR with nulls in my code.
Is this a problem with calling conventions of VB and VC++?BSTR and LPSTR?
Thanx in advance
----Sanjeev

 

[palbano]

Sanjeev,

You might try asking this question in a VB forum.

Good luck
-pete

 

[chiph]

ss2905 -
Returning a string as result of a function call is a problem in VB because of the various BSTR, LPSTR, Unicode, and ANSI problems. It's much better if you returned it as an "Out" parameter in the function call.

If you were to do that, in your VB code you'd do the following:
[tt]
Declare sub lib "MyDLL.dll"(ByVal SendAnInteger as Long, ByRef GetAString as string)
[/tt]
Note that all strings need to be passed "Byref" to external DLLs in VB. Also note that 'int' datatype in C++ is a 32-bit value, and needs to be declared as 'long' in VB.

Also Also note, that when VB7 (aka .NET) comes out, this hassle of mis-matched datatypes will go away, since VB and VC++ will use the same runtime libraries.

Chip H.

 

[Guest_imported]

You might try using an
InStr(retStr,0) and see if you can find the end of the character string returned. Then apply the Right (Left??? i forget which, it has been a while) function to modify your string.