I have been looking into replacing Fedora's obsolete version of libpng (1.2.x release series) with something more modern. The possible choices are the 1.4.x and 1.5.x release series. The 1.5.x series adds some more features that 1.4.x did not have, but it also poses significantly more migration problems. The reason is that 1.5.x no longer exposes the contents of the library's internal "png_info" struct. Direct access to fields of png_info has been deprecated for a long time, in favor of using accessor functions, but up through 1.4 you can get away with it. I did test rebuilds in mock of all rawhide packages that are reported to be dependent on libpng. Out of 964 packages with dependencies on libpng, we have: Packages that rebuilt successfully with 1.5 658 Packages that FTBFS for non-libpng reasons 186 Packages that rebuilt with 1.4, but not 1.5 74 Packages that need help even with 1.4 46 (The non-libpng failures seem to mostly be due to the recent upgrade to glib 2.0. Some of those probably have libpng issues as well, but didn't get far enough in their builds to expose them.) About half of the "need help anyway" group may just need their BuildRequires to be rebuilt first --- it looked like they had no source-code dependency, but were just absorbing "-lpng12" from library link flags reported by other packages. I built each package independently rather than trying to chain the builds, so this wasn't catered for. The vast majority of the 74 packages that would need extra work if we move to libpng 1.5 are trying to access the png_info struct directly, and so would need patches to use the accessor functions instead. This is work that should be done and upstreamed anyway, but if we move to 1.4 we would not have to do it Right Now. It looks like it would be a fairly large amount of work, too --- I count 1164 "incomplete type" failures in the build logs for those packages, and it's quite likely there are more in source files that the build runs didn't get to. On the other hand, if we move to 1.4 there will not be any pressing reason for these fixes to get made, and so I'm not sure that we'll be any better off when we try to move to 1.5 later. Another point is that we'd have to build these same 964 packages over again if we plan a two-stage upgrade. Any opinions on which way to jump? In either case, as per the discussion at http://lists.fedoraproject.org/pipermail/devel/2011-October/157712.html I plan to provide the 1.2.x libpng shared library (and only the library, not its devel support files) in a libpng-compat subpackage for the time being. So existing programs that depend on 1.2.x will continue to work, but it won't be possible to rebuild a package that has source-level dependencies on 1.2.x until those are fixed. I think this is enough to avoid needing a special build tag for staging the rebuilds. regards, tom lane -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
