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Defining a shared data segment in a dll using Borland C++ compiler

Posted on 2003-11-05
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Last Modified: 2013-12-14
Is there a way to define a shared data segment in a DLL using Borland C++5.5 compiler. Apparently it doesn't support the VC++ #pragma data_seg(). I would greatly appreciate an example.

Thank you in advance,
Alex
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Comment
Question by:FireClown
6 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 9688501
See the sample at http://community.borland.com/article/0,1410,20008,00.html 

To change the data segment and the class name, you need to add #pragma option -zR[SEGMENT NAME] and #pragma option -zT[CLASS NAME] to the file you want the data shared from. Below is the source file I am going to export the integer named 'data':

File: SharedData.cpp
//---------------------------------------------------------------------------
// Borland C++Builder
// Copyright (c) 1987, 1999 Inprise Corporation. All Rights Reserved.
//---------------------------------------------------------------------------

#pragma option -zRSHSEG      // change default data segment name
#pragma option -zTSHCLASS    // change default data class name

// Here is the initialized data that will be shared.
int data = 0;

Notice that the segment name for this file is: SHSEGSHCLASS. A .def file is required for the linker to create the shared segement. Below is what the .def file looks like:

File: Shared.def
LIBRARY SHAREDDLL

SEGMENTS
  SHSEG CLASS 'SHCLASS' SHARED

Below is the header and source file for the DLL which contains the entry point into the DLL, and the setters and getters for the 'data' variable in the shared memory space:

File: SharedDLL.h
//---------------------------------------------------------------------------
// Borland C++Builder
// Copyright (c) 1987, 1999 Inprise Corporation. All Rights Reserved.
//---------------------------------------------------------------------------

#ifdef __DLL__
#define DLL_EXPORT __declspec(dllexport)
#else
#define DLL_EXPORT __declspec(dllimport)
#endif

extern "C"
{
void DLL_EXPORT SetData(int x);
int DLL_EXPORT GetData(void);
}

File: SharedDLL.cpp
//---------------------------------------------------------------------------
// Borland C++Builder
// Copyright (c) 1987, 1999 Inprise Corporation. All Rights Reserved.
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
#include
#pragma hdrstop

#include "Shared.h"
//---------------------------------------------------------------------------
//   Important note about DLL memory management when your DLL uses the
//   static version of the RunTime Library:
//
//   If your DLL exports any functions that pass String objects (or structs/
//   classes containing nested Strings) as parameter or function results,
//   you will need to add the library MEMMGR.LIB to both the DLL project and
//   any other projects that use the DLL.  You will also need to use MEMMGR.LIB
//   if any other projects which use the DLL will be perfomring new or delete
//   operations on any non-TObject-derived classes which are exported from the
//   DLL. Adding MEMMGR.LIB to your project will change the DLL and its calling
//   EXE's to use the BORLNDMM.DLL as their memory manager.  In these cases,
//   the file BORLNDMM.DLL should be deployed along with your DLL.
//
//   To avoid using BORLNDMM.DLL, pass string information using "char *" or
//   ShortString parameters.
//
//   If your DLL uses the dynamic version of the RTL, you do not need to
//   explicitly add MEMMGR.LIB as this will be done implicitly for you
//---------------------------------------------------------------------------
USEUNIT("SharedData.cpp");
USEDEF("Shared.def");
//---------------------------------------------------------------------------
int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void*)
{
   return 1;
}
//---------------------------------------------------------------------------
extern int data;

//---------------------------------------------------------------------------
void DLL_EXPORT SetData(int x)
{
  data = x;
}
//---------------------------------------------------------------------------
int DLL_EXPORT GetData(void)
{
  return data;
}
//---------------------------------------------------------------------------

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Author Comment

by:FireClown
ID: 9689170
Thank you for a quick response,
I saw that article, but it applies to Borland C++ 4.0. The new compiler does not accept the -zR and -zT options for some reason. I therefore assumed that they designed another way of doing this and forgot to document it.
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LVL 30

Expert Comment

by:Axter
ID: 9691265
Try using MapView API functions instead.

MapView API functions work on any Win32 compiler.
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Accepted Solution

by:
GloomyFriar earned 125 total points
ID: 9693245
It's not an excellent way, but you can change section flags after compilation and linking with using program like "Lord PE":
http://scifi.pages.at/yoda9k/LordPE/info.htm
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Author Comment

by:FireClown
ID: 9710074
Thank you Axter, but I really need to get the sections defined the way VC++ lets me do it.
Thank you GloomyFriar it appears to require some extra fiddling, but works
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LVL 30

Expert Comment

by:Axter
ID: 9711724
>> I really need to get the sections defined the way VC++ lets me do it.

VC++ lets you use MapView API functions.
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