[gentoo-user] How does autotools/emerge/revdep-rebuild pick libraries when dependency-checking/compiling? (libpng12/14)

[Mark David Dumlao]

I'm installing a 3rd party binary on my system (odesk team) from here:
http://www.odesk.com/community/linux

I remember last time I just picked the latest 64bit fedora version,
extracted their stuff, and placed it somewhere in opt. Recently
though, the app has been giving me some trouble, so I checked if there
was a later version and I was 3 minor revisions behind. Whoops! The
latest fc version depends on libpng12.

I still remember that whole libpng12 recompile nightmare a couple
months back that forced me to do a near equivalent of emerge -e...
hundreds of compiles, circular fails, some manual sedding,
lafilefixer, revdeps, and all that gentoo fun later and I've gotten me
to a pure libpng14 system in about a week. whoopee!

I'll probably try the arch version instead, but I'm curious now. If
ever I should install libpng12 (slotted to 1.2), what happens on my
next emerge? Configure will use a libpng version to use for compiles,
but which one will it use? Will my system still be mostly on libpng14
or is there a chance that some recompiles go back to libpng12? Havng
spent so much energy getting it one way I'd rather not have it
reversed.
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