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