bug#10578: 24.0.92; No png images on OpenSUSE 12.1

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>> 2) If I have both libpng12 and 14 installed, why is Emacs building
>>> against 14 and then preferring 12 when running?
>> Because Emacs on GNU/Linux doesn't use the kind of machinery it does
>> on MS-Windows, whereby it will reject 12 if it was compiled against
>> 14.  See w32-win.el:dynamic-library-alist, and in particular how it
>> consults the variable libpng-version (which is set at compile time).
> Right.  From what ldd said, it seemed like it was (dynamically) linked
> against both lippng12 and 14, which seems odd to me.  Is that a bug?

Emacs probably links against one of the two, and then one of the other
libs used by Emacs (e.g., Gtk) link to the other one.

> Anyway, this is the first time I've seen something like this.  My home
> machines usually grow very old and get a lot of different versions of
> various libraries over the year, but compilation of stuff usually
> doesn't fail just because of that.

My machines also accumulate stuff like that and I rarely bump into the
problem, but it can happen.


        Stefan