libpng transition?

Emmanuel Hainry milosh at
Sat Jan 22 00:43:20 PST 2011

Citando Jack Howarth :
> On Fri, Jan 21, 2011 at 05:25:46PM -0800, Bradley Giesbrecht wrote:
> >
> > Putting your local repository ahead of rsync in sources.conf provides a 
> > valuable method of preventing software from being upgraded.
> That would be a valuable method if MacPorts had the version dependency
> checking at the package level to prevent breakage like I witnessed with
> pymol vs libpng. Currently it is more of a high risk strategy as it leaves
> you open to soversion mismatches.

According to Ryan's first answer to your question, 

"When a port changes its library version number, all ports that use
that library need to be rebuilt. This is handled by increasing the
revision of those ports. For a central library like libpng, this means
many many ports receive a revision bump."

It means that maitainers are supposed to act. If you have a local
Portfile, you maintain your own version of pymol. Hence you are
supposed to revbump your Portfile. Yes being a maintainer is
sometimes fastidious, and can be risky if you don't do it properly.

Also, note that pymol does not require libpng to be 1.4 or 1.2, it
builds very well with either version, so version dependency would not
change anything to your problem. If someone has a local libpng port
blocked at his favorite version 1.2.x, he can however build pymol
without modifying pymol's portfile.


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