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Mail Archives: cygwin-apps/2002/04/19/03:33:03

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From: "Ralf Habacker" <Ralf DOT Habacker AT freenet DOT de>
To: "Cygwin-Apps" <cygwin-apps AT cygwin DOT com>
Subject: RE: FW: libtool devel package still dll crippled.
Date: Fri, 19 Apr 2002 09:31:11 +0200
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In-Reply-To: <200204181338.42655.bastian@kde.org>

> > 1. When someone build a shared lib on linux and uses a static lib, are the
> > symbols of the static lib automatically  exported ?
> Yes, using a static lib is no different than compiling that code
> directly into your codebase.

Thats the behavior we have on cygwin, isn't it

> > 2a. If yes, and if someone build a second dll with the same static lib, the
> > symbols of the static libs are in both
> > shared lib defined. Then if someone uses these two shared libs to build for
> > example an application, ld fails with duplicated symbol errors. How does ld
> > prevent this ?
> ld checks the symbols in the shared libs during compile time to see if it can
> resolve all symbols and appearantly also detects duplicated symbols. On Linux
> it is not necassery impossible to have two libs that define the same symbols.
> E.g. this feature can be used to override the malloc implementation of libc.
> Of course when this happens inadvertently it can lead to unexpected
> behaviour/crashes. ELF (The linking format used on Linux) has rather complex
> rules for determining which symbol should be used if it is defined multiple
> times. It also distinguishes between weak and strong symbols. It might be
> that it is only possible to override weak-symbols and that multiple
> strong-symbols result in link-errors.

Does the cygwin ld has some similar rules ?

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