[fpc-devel] Dynamically Loading Libraries

[Leonardo M. Ramé]

Regarding a similar subject, I found an article by Hallvards Vassbotn showing a method to delay load dlls in Delphi, its usage is pretty similar to static linking, but the library is loaded on demand (without explicitly calling LoadLibrary).

This is a short version: http://hallvards.blogspot.com/2008/03/tdm8-delayloading-of-dlls.html

The long PDF version: http://vassbotn.googlepages.com/DelayLoadingOfDLLs.pdf

Leonardo M. Ramé
http://leonardorame.blogspot.com


--- On Wed, 11/11/09, Marco van de Voort <marcov at stack.nl> wrote:

> From: Marco van de Voort <marcov at stack.nl>
> Subject: Re: [fpc-devel] Dynamically Loading Libraries
> To: "FPC developers' list" <fpc-devel at lists.freepascal.org>
> Date: Wednesday, November 11, 2009, 8:54 AM
> In our previous episode, Jeppe
> Johansen said:
> > >>     procedure proc;
> external name 'proc';
> > >> denotes a static linked function.
> > >>     
> > >
> > > This syntax is not possible. The external 'xxx'
> name 'proc' is there for a reason,
> > > for systems with multiple linker namespaces.
> Moreover there is already an
> > > enormous codebase that uses this.
> > >   
> > I don't know if I'm making a fool of myself, but what
> systems? Skimming 
> > the sources, I couldn't find any mention of it in the
> ELF writers. An 
> > external symbol will simply be linked to the first
> occurrence of a 
> > matching symbol in the first shared or static
> object(unless there's some 
> > name mangling going on that I didn't spot). The COFF
> writer already does 
> > it the way I suggested.
> 
> Windows, Darwin, and afaik Solaris. The ELF writers are
> probably not updated
> for Solaris yet.
> 
> > >> This is ofcourse a solution that would
> require modification of the 
> > >> compiler, but I think in the long run that
> it'll make alot of things 
> > >> more comprehensible
> > >
> > > I don't. I think this dynamically loading of
> headers has already gone to
> > > far. It is a good workaround for a few headers
> that are versionwise a
> > > disaster, like MySQL, but universally, it doesn't
> solve problems.
> > >   
> > In principle, doing it this way would make cross
> compiling to an ELF 
> > platform with dynamic linking easier, once the
> internal ELF linker is 
> > made. 
> 
> While partially true, this is a brute force approach.
> Having a few simple
> map files (that can be generated on target from the libs)
> over which files
> contain which symbols might help too. 
> 
> 
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