Re: Would like some help fixing bug in TclMagick

Bob Friesenhahn <[email protected]>
Newsgroups gmane.comp.video.graphicsmagick.help
Message-ID <[email protected]>
On Fri, 14 Apr 2017, Computer Jock wrote:

> I'm curious, why the change:
>
> 2016-12-31  Bob Friesenhahn  <[email protected]>
>
>    * generic/Makefile.am: Applied patch by Massimo Manghi (plus some
>    fixes by me) to add a 'libttkcommon' shared library to contain
>    codde common to the TclMagick/TkMagick loadable modules, and
>    particularly to allow TkMagick to access TclMagick functions
>    without depending on dlopen() with RTLD_GLOBAL behavior.
>
> If a DLL or SO could not refer to functions defined in a dependent DLL/SO, 
> how would anything work? ie. On windows (using dll's from Msys2/MinGW):

If two libraries link with another library, then each can see that 
library's symbols but not necessarily each other's symbols.  It is not 
assured that libraries/modules see each other's symbols just by being 
loaded in a particular order (which is the assumption when TclMagick 
was originally written).

Linux decided to make it the default that if a shared module is 
loaded, it can not resolve symbols from previously loaded modules. 
This decision improves security, reliability, and namespace isolation, 
but might lessen convenience.

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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