Windows DLLs with Harbour code
Programs created with Clipper or Harbour are traditionally a
monolithic EXE containing all executable code. This includes
the Virtual Machine (VM) and the RunTime Library (RTL) as well as
your own code. Running under Windows with Harbour, you
can now also create and use Windows DLLs that contain PRG code.
Harbour supports Windows DLLs in 3 ways.
1) Self-contained DLLs containing functions from any platform.
(These are not what we call a "harbour.dll", although they may
be named that. The DLL entry points are different.)
These have the VM/RTL inside them and can be used by any other
Windows program. You can create a .lib for static linking,
or use GetProcAddress as in any standard Windows DLL.
Calling Harbour/Prg functions directly is limited to
those that take no parameters unless you include C functions
in the DLL that take parameters and then call the PRG-level
To do static linking, do this to create the .lib:
implib harbour.lib harbour.dll
For the Borland C platform, use that library and import32.lib
and cw32.lib from Borland, and you are ready to go.
2) PCode EXEs using a Harbour.dll
A Harbour.dll is designed to be called from a Harbour app.
A pcode EXE is a small Harbour executable that does not contain the
VM/RTL. To execute its functions, it must load and access a
If you want dynamic linking, then use this to execute a Harbour
dynamically loaded pcode DLL function or procedure:
This lets you have all your common code in a DLL, and have lots
of small EXEs that use it. Realize however that, even though this
may be a nice way to manage your code, each EXE may
load its own image of the Harbour.dll into memory at runtime.
In terms of Windows memory, there may not be a benefit to using pcode
EXEs over monolithic EXEs. But it may be a worthwhile maintenance
benefit to have lots of replaceable small exes.
3) PCode DLLs used from traditional EXEs
A pcode DLL does not contain the VM/RTL.
It is a library of Harbour-compiled PRG code that uses the VM/RTL
of the EXE that calls it. This has the benefit of having
replaceable modules in DLLs that don't necessarily require updating
The following is clipped from a msg by Antonio Linares to the Harbour
developer list explaining some of the details:
Please notice that there are three different Windows DLL entry points:
* maindll.c Windows self-contained DLL entry point
* maindllh.c Windows Harbour DLL entry point (harbour.dll)
* maindllp.c Windows pcode DLL entry point and VM/RTL routing functions
> * maindll.c Windows self-contained DLL entry point
To produce Harbour code, as DLLs, that may be used
from other programming languages applications (as VB,
Delphi, C++, etc...)
> * maindllh.c Windows Harbour DLL entry point (harbour.dll)
To produce Harbour.dll, to be just used from small pcode Harbour EXEs
> * maindllp.c Windows pcode DLL entry point and VM/RTL routing
To produce small pcode DLLs, to be used just from Harbour EXE apps.
maindllp.c is the entry point for the Harbour pcode DLLs. pcode DLLs
are quite small DLLs, that just contain pcode and/or C (using extend
mainwin.c is the entry point for Windows EXEs, not for DLLs.
You may use maindll.c, maindllh.c or maindllp.c based on
If you are looking to build a Harbour.dll, then you must use