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Re: Incompatibilities between home-compiled and apple's libpng
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Re: Incompatibilities between home-compiled and apple's libpng


  • Subject: Re: Incompatibilities between home-compiled and apple's libpng
  • From: Andreas Grosam <email@hidden>
  • Date: Wed, 12 Oct 2005 17:54:49 +0200


On 11.10.2005, at 12:09, Damien Bobillot wrote:


Peter O'Gorman wrote :

D. Walsh wrote:

This doesn't work by mistake, it works because you are repackaging a static library as a dynamic library and providing the current and compatibility information.

There already was a dynamic shared library with the correct current and compatibility versions though, making up different numbers to solve the problem is not right, I feel.

The existing library with the same name cannot be used, because it does not export the same symbols. So I MUST compile my own version of the libpng.
I think, it's not supposed to be used. This library libPng.dylib is located in a private framework (ImageIO) within the framework ApplicationServices (only in 10.4, in previous system versions this may be different!).


Meanwhile, I've found an obvious solution to my problem : just adding the static lib libpng.a to my project... (300Ko is not so much).
Sure, this is the solution ;-)
... or just install libpng with darwinports and build static and dynamic versions. Then, in your app link against this lib.



The real issue is that Apple uses the opensource libpng library, but don't export the png_* symbols. So it's impossible to use this library in our programs without any hacks. Why Apple don't
make it publicly available ? (may be off topic...)
Most likely because Apple want to use this lib *privately*. This is a common use case. I know several other libraries that link (mostly statically) against a local copy of another open source library. The reasons may be:
- customized sources
- non-default configure options
- newest sources needed (cvs, unstable)
- independence of other installation paths and the existence of this libs
- etc,


If you find this library usefull, feel free to install it by yourself.


Anyway, I think the original poster has DYLD_LIBRARY_PATH set somewhere to be getting this behavior.

I do. However, if I put my library in /usr/lib, I don't need DYLD_LIBRARY_PATH anymore. So my problem has nothing to do with DYLD_LIBRARY_PATH.

/usr/lib is owned by system, you should not touch these folders/files.

You should better install the library from the package (using configure/make/make install) in usr/local or another "prefix" e.g. /opt/local.

Or better, use one of the package managers Darwinports or Fink to install third party libs:
<http://darwinports.opendarwin.org/> (currently down!?)
<http://fink.sourceforge.net/>



Andreas


-- Damien Bobillot


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References: 
 >Incompatibilities between home-compiled and apple's libpng (From: Damien Bobillot <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: "D. Walsh" <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: Damien Bobillot <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: "Peter O'Gorman" <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: "D. Walsh" <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: "Peter O'Gorman" <email@hidden>)
 >Re: Incompatibilities between home-compiled and apple's libpng (From: Damien Bobillot <email@hidden>)

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