From: Andrey Borzenkov <arvidjaar@newmail.ru>
To: zsh-workers@sunsite.dk
Subject: Re: Library linkage portability?
Date: Sun, 29 Apr 2007 20:09:24 +0400 [thread overview]
Message-ID: <200704292009.24714.arvidjaar@newmail.ru> (raw)
In-Reply-To: <070429084431.ZM5861@torch.brasslantern.com>
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On Sunday 29 April 2007, Bart Schaefer wrote:
> On Apr 29, 5:34am, Phil Pennock wrote:
> }
> } Can someone please educate me as to the issues, or have I summed it up?
> } What about the stranger platforms, AIX etc?
>
> Search the zsh-workers archives for the years 1996-1998 for the terms
> "dynamic;link" "dynamic;load" and "dynamic;library". E.g.:
>
> http://tinyurl.com/3355m6
>
> In particular start here:
>
> http://tinyurl.com/37gaqe
>
> My recollection is that Cygwin and some other environments require not
> that dynamic modules be linked from the main executable, but that they
> be linked from another library, which is why the zsh/main module exists.
>
More precisely - some systems cannot export dynamic symbols (necessary for
run-time linking) from main executable; they can be exported only from
another dynamic module; library just being special case of dynamic module. I
have been using such system for some time. Because on Win32 you actually link
DLL against stub for another DLL, and such stub exists for DLL only, not for
exe, I guess it is true for Cygwin as well (modern Cygwin can generate stub
on the fly, but it is still required).
Also there are systems that do not support chained libraries (i.e. main
executable requires library liba.so which requires libb.so. In this case
libb.so won't be loaded unless explicitly listed during linking of main
executable. Whether linker does not put NEEDED entries or rtld ignores them,
does not matter - I believe on my system it was the latter). That is actually
what gave rise to something like "pkgcofig --libs ..."; also libtool should
cope with this too - it has full information about all requirements and links
main executable against all need libraries on systems that need it.
I do not know if you can find any such system in the wild today.
-andrey
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prev parent reply other threads:[~2007-04-29 16:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-29 12:34 Phil Pennock
2007-04-29 15:44 ` Bart Schaefer
2007-04-29 16:09 ` Andrey Borzenkov [this message]
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