From:	sl AT psycode DOT com DOT REMOVE_THIS
Newsgroups:	alt.msdos.programmer,comp.os.msdos.djgpp,comp.os.msdos.programmer
Subject:	Re: DOS-based DLL system
Date:	14 Oct 1998 11:30:57 GMT
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On Tue, 13 Oct 1998 17:54:34, Ilya Ryzhenkov <orangy AT inetlab DOT com> 
wrote:

> IMHO the world is much brighter than you described. The Ultimate DOS
> Dynamic
> Load Library Which Will Deal With Any DOS Programs - yes, it's a beast
> hard
> to implement. But if we are speaking of a particular compiler and
> library
> to dynamicaly load code - I see not so much problems. At first you
> should
> see, that one can safely call DATA in DOS environment - so you can
> simply
> alloc some memory, load DLL image into it, then get symbol address
> (somehow -
> depends on the DLL layout and your goals) and call the pointer. That is
> how
> it was done in Windows DLL system - you ask to load dll, then ask for
> pointer
> to function and then just call it via pointer. Import lib funcs are just
> wrappers to this scheme. 
> Another way is to create a wrap to the whole program - as it was done in
> my DLM engine. Special stub starts before all your code and creates the
> dynamic environment. What it actually load are object files. It resolves
> symbols and call the main. It also export LoadDLM and other API
> functions
> for modules to be able to access DLM engine features. 
>  
> As you see no TSR or DOS hacking required.
> 
> > The whole thing is utterly inefficient since dynamic linking was
> > designed for sharing one copy of library among different address spaces.
> > In DOS there is a single-tasking environment so DLL system will eat up a
> > lot of memory, saving nothing. What do you need it for, what is the
> > design goal?
> 
> There are much more reasons to use dynamic linking/loading than you
> mentioned.
> They include :
>  - loading drivers - are you going to link in your exe ALL possible
> drivers and
>    thus make you program unextendable ? Or you prefer to make several
> DRV/DLL/DLM's
>    which share interface and contain code specific for the device ?
>  - plugins - common object interface will help you to create installable
> plugins
>  - overlays. In low memory environment you can load/unload parts of you
> program as
>    needed.
>  - there are some more. anyone can easely continue the list.

	I agree with you.. We *do* need DLL support in DOS ;) But are you 
planning to make this an official (supported) project? I would love to
see DLL support built into future versions of DJGPP..

Gili

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