C/C++ import libraries for PBDLL - Revisited

[Cecil Williams]

This is in response to Peter Stephensen's post below dated 11-22.
This describes creating an import library for C/C++ programmers
to be able to link into and use PB DLLs. I did not realize
why Peter was using the "mangled" aka "decorated" functions in
the PB alias until I down loaded the source files. It is NOT
necessary to go to that much trouble, in fact it's double work, in
polling the linker to get the decorated value in C++.

I am going to leave out the semantics of using MSDEV here and
just list Peter's code modified. This would be a good example
for the new PB offering to list as a reference in the next
release.

1. Create the PB DLL:

#COMPILE DLL
#INCLUDE "WIN32API.INC"

 FUNCTION LibMain(BYVAL hInstance   AS LONG, _
                  BYVAL fwdReason   AS LONG, _
                  BYVAL Reserved    AS LONG) EXPORT AS LONG

     SELECT CASE fwdReason
       CASE %DLL_PROCESS_ATTACH
             FUNCTION = 1
             EXIT FUNCTION
       CASE %DLL_PROCESS_DETACH
            EXIT FUNCTION
       CASE %DLL_THREAD_ATTACH
            EXIT FUNCTION
       CASE %DLL_THREAD_DETACH
            EXIT FUNCTION
    END SELECT
 END FUNCTION

 SUB TestFunc1 CDECL ALIAS "TestFunc1" (s AS ASCIIZ) EXPORT
    MSGBOX s
 END SUB

 FUNCTION TestFunc2 CDECL ALIAS "TestFunc2" (BYVAL x AS LONG) EXPORT AS LONG
    FUNCTION = 2*x
 END FUNCTION

Notice the non-decorated alias in the above functions. Decorated
functions in C++ only are for overloaded functions which do not
work in PB.

2. Next compile the above code to a DLL.

3. Now, write the C header file for the PB functions:

#ifndef MYAPP_H
#define MYAPP_H

#ifdef __cplusplus
extern "C" {
#endif

void TestFunc1( char * );
int  TestFunc2( int );

#ifdef __cplusplus
}
#endif

#endif //MYAPP_H

Notice that we now have control over this header file if we are
compiling in C++ context. The extern "C" adder now forces C
linkage. The compiler uses standard C convention in decorating
the functions with a leading underscore. Not worried about this.

4. Create a console app in C++ to display our use of the PB DLL.

// TestLib.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "MyApp.h"

int main(void)
{
	char buffer[30];
	int y = 0;

	strcpy( buffer, "This is written in C++!" );
	
	TestFunc1( buffer );

	y = TestFunc2( 2 );
	_itoa( y, buffer, 10 );
	
	strcat( buffer, " is the product 2 X 2" );

	TestFunc1( buffer );

	return 0;
}

5. Create a definition file for the LIB utility program in VS6:

LIBRARY      Myapp

EXPORTS
             TestFunc1
             TestFunc2

6. Call LIB from an MSDOS command prompt as follows:
LIB /DEF:Myapp.def

7. We now have the import lib Myapp.lib and export file Myapp.exp

8. Compile and execute the above C++ file.

And that's all there is to it. You can supply a PB DLL in usable
form to C and C++ developers in the manner they expect.

Also, be mindfull of one fact, C/C++ is case sensitive so function
names must match exactly.

Cheers,
Cecil


------------------

[Peter P Stephensen]

Cecil,

I had the feeling that there had to be a non-decorated 'C-way'
to make the lib. Thanks for showing how.

Regards
Peter

------------------

[John Hackl]

here's how i got the above going in vc5.

1. create the files myapp.bas, myapp.def, myapp.h, testlib.cpp from above
2. in pb compile myapp.dll
3. from the dos prompt, find and run vcvars32.bat
4. from the dos prompt, lib /def:myapp.def
5. in vc5, file open testlib.cpp
6. comment out /* #include "stdafx.h" */ in testlib.cpp
7. build compile testlib.cpp, let vc5 add new project workspace
8. project add file myapp.lib
9. build build testlib.exe
10. copy myapp.dll to \debug\
11. in \debug\ testlib

some other info at: http://www.powerbasic.com/support/pb...ead.php?t=5457
and http://www.powerbasic.com/support/pb...ead.php?t=2330