expecting a user to use `port select` from a Portfile (re: Qt 5 support on OS X 10.6)

[René J.V. Bertin]

Hello,

I've managed to get Qt 5.3 to build on OS X 10.6 and adapt my qt5-mac-devel Portfile for that. No small feat, as this is not officially supported by Digia. Main issue here: the system compilers on 10.6 (*gcc-4.2, and clang from Xcode 3.2 as well as Xcode 4.2) are incapable of building Qt 5.3 and care must thus be taken not to use them accidentally.

This requires a modern version of clang, and in order to avoid ending up with a hard-wired clang version dependency my current approach instructs the user to use `port select` (or equivalent). The actual requirement is to have a modern compiler in the path (I've only tested with clang because that's what Qt 5.3 builds with on supported OS X versions). My own requirement is that there be no version information in the compiler name, in order to avoid said hard-wired dependencies and unnecessary rebuilds.

I caught flak on my trac ticket for "requiring" port select, despite IMHO conforming to its intended use, i.e. user convenience. This requirement takes the form of testing for ${prefix}/bin/clang{,++} and aborting with instructions if those items are missing. Those would normally be one-time instructions, of course.

What other approaches are there? I can only see a few

- Change the rewriting of several Qt build script/config files so that they don't contain a full path to ${prefix}/bin/clang{,++}, presume that ${prefix}/bin will always and reliably be first in the path, and cross eyes, fingers and toes that everything builds correctly. Qt and Qt applications alike. 

- Hack the build system even more in order to provide a Qt-specific equivalent for the port select mechanism.

- Drop the idea of supporting OS X 10.6 in an official port

If I'm missing something obvious and more elegant than asking the user to use `port select` I'd love to hear about it, but as things stand I think it's the best compromise that doesn't even violate official dogma.

BTW, it would also be about time to publish this port (and qt4-mac) so that more users can start installing and testing Qt4 and Qt5 applications alongside.

The current port directory: https://trac.macports.org/attachment/ticket/46536/port%3Dqt5-mac-devel.tar.bz2

R.