| Author |
Message |
|
Chris Fran
#1 / 11
|
 Calling a function in a C++ Win32 Dll from VB 6 I am trying to write a Win32 DLL using Visual C++. Whenever I try to call a function from VB 6 I get an "Entry point not found" error. I can call the function from C++ with no problems. Is there a way to write
a Win32 DLL that VB can access or do I have to Write an ATL COM object?
Any sample code would be very helpful.
Thanks
Chris
|
| Fri, 13 Dec 2002 03:00:00 GMT |
|
 |
|
Jonathan Woo
#2 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 You need to create a DEF file that includes all your exports. However, if this is C++ code and not C, then you need to deal with the issue
of name mangling, which C++ implements to keep overloaded function names
unique.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
Quote: > I am trying to write a Win32 DLL using Visual C++. Whenever I try to call a > function from VB 6 I get an "Entry point not found" error. > I can call the function from C++ with no problems. Is there a way to
write
> a Win32 DLL that VB can access or do I have to Write an ATL COM object?
> Any sample code would be very helpful.
> Thanks
> Chris
|
| Fri, 13 Dec 2002 03:00:00 GMT |
|
|
|
Ray Merce
#3 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 The DEF file *is* how you deal with name mangling. There is an example C-DLL and VB project called RoundMe in my code sample
section:
Hope this helps,
Ray Mercer
www.shrinkwrapvb.com
Quote: > You need to create a DEF file that includes all your exports. > However, if this is C++ code and not C, then you need to deal with the
issue
> of name mangling, which C++ implements to keep overloaded function names
> unique.
> --
> Jonathan Wood
> SoftCircuits Programming
> http://www.softcircuits.com
> > I am trying to write a Win32 DLL using Visual C++. Whenever I try to
call
> a
> > function from VB 6 I get an "Entry point not found" error.
> > I can call the function from C++ with no problems. Is there a way to
> write
> > a Win32 DLL that VB can access or do I have to Write an ATL COM object?
> > Any sample code would be very helpful.
> > Thanks
> > Chris
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Chris Fran
#4 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Thanks! I got it to work. Now on to the hard stuff.
Quote: > The DEF file *is* how you deal with name mangling. > There is an example C-DLL and VB project called RoundMe in my code sample
> section:
> Hope this helps,
> Ray Mercer
> www.shrinkwrapvb.com
> > You need to create a DEF file that includes all your exports.
> > However, if this is C++ code and not C, then you need to deal with the
> issue
> > of name mangling, which C++ implements to keep overloaded function names
> > unique.
> > --
> > Jonathan Wood
> > SoftCircuits Programming
> > http://www.softcircuits.com
> > > I am trying to write a Win32 DLL using Visual C++. Whenever I try to
> call
> > a
> > > function from VB 6 I get an "Entry point not found" error.
> > > I can call the function from C++ with no problems. Is there a way to
> > write
> > > a Win32 DLL that VB can access or do I have to Write an ATL COM
object?
> > > Any sample code would be very helpful.
> > > Thanks
> > > Chris
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Jonathan Woo
#5 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Ray, Quote: > The DEF file *is* how you deal with name mangling.
Huh? Since I write my DLLs in C or assembler, I do in fact use a .DEF file to
deal with the underscore, etc. normally prepended to function names.
However, real C++ name mangling (the type used to keep overloaded function
named unique) cannot be resolved with a .DEF file. I brought that up because
it was not clear to me if the original poster was writing the DLL in C++.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
Quote: > The DEF file *is* how you deal with name mangling. > There is an example C-DLL and VB project called RoundMe in my code sample
> section:
> Hope this helps,
> Ray Mercer
> www.shrinkwrapvb.com
> > You need to create a DEF file that includes all your exports.
> > However, if this is C++ code and not C, then you need to deal with the
> issue
> > of name mangling, which C++ implements to keep overloaded function names
> > unique.
> > --
> > Jonathan Wood
> > SoftCircuits Programming
> > http://www.softcircuits.com
> > > I am trying to write a Win32 DLL using Visual C++. Whenever I try to
> call
> > a
> > > function from VB 6 I get an "Entry point not found" error.
> > > I can call the function from C++ with no problems. Is there a way to
> > write
> > > a Win32 DLL that VB can access or do I have to Write an ATL COM
object?
> > > Any sample code would be very helpful.
> > > Thanks
> > > Chris
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Mattias Sj?gr
#6 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Jonathan & Ray, Quote: >Since I write my DLLs in C or assembler, I do in fact use a .DEF file to >deal with the underscore, etc. normally prepended to function names. >However, real C++ name mangling (the type used to keep overloaded function
>named unique) cannot be resolved with a .DEF file. I brought that up because
>it was not clear to me if the original poster was writing the DLL in C++.
Correct me if I'm wrong, but I don't think C vs. C++ matters here. It's the calling convention that does it, isn't it? _stdcall functions get the name
And that can be "unmangled" by a DEF file. Whether or not it works for
other calling conventions seems irrelevant in this case, since VB only
supports _stdcall.
Mattias
____________________________________________
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Jonathan Woo
#7 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Mattias, Quote: > Correct me if I'm wrong, but I don't think C vs. C++ matters here. > It's the calling convention that does it, isn't it? _stdcall functions > get the name
> And that can be "unmangled" by a DEF file. Whether or not it works for
> other calling conventions seems irrelevant in this case, since VB only
> supports _stdcall.
True C++ functions employ their own name mangling. How do you suppose the linker resolves overloaded functions? int myfunc(char *p);
int myfunc(int i);
.DEF files have no say over this unless someone knows something I don't
here.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Mattias Sj?gr
#8 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Hi Jonathan, Quote: >True C++ functions employ their own name mangling. How do you suppose the
>linker resolves overloaded functions?
Darn.. yes, of course you're right. Sorry you had to write that three times for me to believe it :-) Back to your previous post then:
Quote: >However, real C++ name mangling (the type used to keep overloaded function
>named unique) cannot be resolved with a .DEF file.
That's not completely true however. And this time I'm pretty sure, because I just tried it :-) It requires a bit more work, and of course you can't export the functions with the same name, but it *is* possible. First export them using _declspec(dllexport). Use Dependency Walker,
Dumpbin or similar tool to get the decorated name. Put it in the DEF
file, remove the _declspec(dllexport) statements and rebuild.
Here's what I tested with:
--- CPP file ---
int _stdcall func1(char* s)
{ /* ... */ }
int _stdcall func1(int i)
{ /* ... */ }
--- DEF file ---
EXPORTS
Mattias
____________________________________________
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Jonathan Woo
#9 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Mattias, Quote: > EXPORTS
Yep, that's what I was looking for. Hadn't tried that since I have never used C++ to write DLL libraries to be called from VB. However, I still consider it a bit of a pain, if you ask me, to find what
the mangled names are, and that they can change if you compile with a
different C++ compiler.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Berger, Kristo
#10 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Hi! Use stdcall calling-convention.
Cheers
Kristof
Quote: -----Original Message-----
Posted At: Dienstag, 27. Juni 2000 02:49
Posted To: winapi
Conversation: Calling a function in a C++ Win32 Dll from VB 6
Subject: Re: Calling a function in a C++ Win32 Dll from VB 6
You need to create a DEF file that includes all your exports.
However, if this is C++ code and not C, then you need to deal with the
issue
of name mangling, which C++ implements to keep overloaded function names
unique.
--
Jonathan Wood
SoftCircuits Programming
http://www.softcircuits.com
> I am trying to write a Win32 DLL using Visual C++. Whenever I try to
call
a
> function from VB 6 I get an "Entry point not found" error.
> I can call the function from C++ with no problems. Is there a way to
write
> a Win32 DLL that VB can access or do I have to Write an ATL COM
object?
> Any sample code would be very helpful.
> Thanks
> Chris
|
| Sat, 14 Dec 2002 03:00:00 GMT |
|
|
|
Ray Merce
#11 / 11
|
Calling a function in a C++ Win32 Dll from VB 6 Hi Jonathon, Quote: > > The DEF file *is* how you deal with name mangling. > Huh?
> Since I write my DLLs in C or assembler, I do in fact use a .DEF file to
> deal with the underscore, etc. normally prepended to function names.
> However, real C++ name mangling (the type used to keep overloaded function
> named unique) cannot be resolved with a .DEF file. I brought that up
because
> it was not clear to me if the original poster was writing the DLL in C++.
This is only an issue if the DLL uses overloaded functions, which the poster made no mention of. As Mattias pointed out you can get around even those with a DEF file, but for the vast majority of C++ DLLs all you need is this: EXPORTS
FunctionName
The linker is smart enough to export the function with that name just as it
is in either C or C++, no need for extern C or anything. The MSVC docs
don't explain this well however and even hint that DEF files are no longer
necessary. However, I have found that they make life *much* easier when
writing DLLs for VB (of course it's not necessary if you are writing the DLL
for C++ use).
If you want to add some options:
LIBRARY DLLName
DESCRIPTION "Cool function library by Joe Blow"
EXPORTS
FunctionOne
FunctionTwo
e.g.,
[Private] Declare Function FunctionOne Lib "DLLName" (ByVal inPut as Long)
as Long
Ray Mercer
MS-MVP Visual Basic
www.shrinkwrapvb.com
|
| Mon, 16 Dec 2002 03:00:00 GMT |
|
| |
